PDMS with designer functionalities—Properties, modifications strategies, and applications

Oral administration microrobots for drug delivery

Oral administration is the most simple, noninvasive, convenient treatment. With the increasing demands on the targeted drug delivery, the traditional oral treatment now is facing some challenges: 1) biologics how to implement the oral treatment and ensure the bioavailability is not lower than the subcutaneous injections; 2) How to achieve targeted therapy of some drugs in the gastrointestinal tract? Based on these two issues, drug delivery microrobots have shown great application prospect in oral drug delivery due to their characteristics of flexible locomotion or driven ability. Therefore, this paper summarizes various drug delivery microrobots developed in recent years and divides them into four categories according to different driving modes: magnetic-controlled drug delivery microrobots, anchored drug delivery microrobots, self-propelled drug delivery microrobots and biohybrid drug delivery microrobots. As oral drug delivery microrobots involve disciplines such as materials science, mechanical engineering, medicine, and control systems, this paper begins by introducing the gastrointestinal barriers that oral drug delivery must overcome. Subsequently, it provides an overview of typical materials involved in the design process of oral drug delivery microrobots. To enhance readers' understanding of the working principles and design process of oral drug delivery microrobots, we present a guideline for designing such microrobots. Furthermore, the current development status of various types of oral drug delivery microrobots is reviewed, summarizing their respective advantages and limitations. Finally, considering the significant concerns regarding safety and clinical translation, we discuss the challenges and prospections of clinical translation for various oral drug delivery microrobots presented in this paper, providing corresponding suggestions for addressing some existing challenges.

Microplastics and nanoplastics released from injection syringe, solid and liquid dimethylpolysiloxane (PDMS)

For a plastic syringe, a stopper at the end of plunger is usually made of polydimethylsiloxane (PDMS, and co-ingredients). To reduce friction and prevent leakage between the stopper and barrel, short chain polymer of liquid PDMS is also used as lubricant. Consequently, an injection process can release solid PDMS debris from the stopper and barrel, and liquid PDMS droplets from the lubricant, both of which are confirmed herein as solid and liquid micro(nano)plastics. From molecular spectrum perspective to directly visualise those micro(nano)plastics, Raman imaging was employed to analyse hundreds-to-thousands of spectra (hyper spectrum or hyperspectral matrix) and significantly enhance signal-to-noise ratio. From morphology perspective to provide high resolution of image, scanning electron microscopy (SEM) was engaged to cross-check with Raman images and increase assignment / quantification certainty. The weak Raman imaging signal of nanoplastics was extracted using image deconvolution algorithm to remove the background noise and average the signal variation. To increase the result's representativeness and avoid quantification bias, multiple syringes were tested and multiple areas were randomly scanned toward statistical results. It was estimated that thousands of microplastics and millions of nanoplastics of solid/liquid PDMS might be injected when using a plastic syringe of 1 mL. Overall, Raman imaging (along with algorithm and SEM) can be helpful for further research on micro(nano)plastics, and it should be cautious to use plastic syringe due to the increasing concern on the emerging contamination of not only solid but also liquid micro(nano)plastics.

Effect of polydimethylsiloxane on the structure and barrier properties of starch/PBAT composite films

This study aimed to investigate the effects of polydimethylsiloxane (PDMS) with a low surface energy on the structure and physicochemical properties of starch/poly (butylene adipate-co-terephthalate) (PBAT) blown films. The film's appearance was not significantly changed after the addition of PDMS. Compared with the films without PDMS, the films with PDMS displayed a smoother surface. A 2% w/w PDMS addition resulted in the maximum mechanical properties (8.10 MPa of strength, 211.00% of modulus) and surface hydrophobicity (87°) of the films. By contrast, the film with 3% w/w PDMS showed the lowest light transmittance, water vapor (2.73 × 10-11 g·cm·cm2·s-1·Pa-1) and oxygen permeability (9.73 × 10-13·cm3·cm·cm-2·s-1·Pa-1), owing to the improved tightness of the matrix, which increased the zigzag path for molecules to pass through. Films with higher PDMS contents effectively extended the shelf life of packaged bananas and shiitake mushrooms, benefiting from the outstanding and appropriate barrier properties, according to principal component analysis results. Findings supported that high-content starch/PBAT films containing PDMS had potential in the preservation of fresh agricultural products.

Molecular behavior of silicone adhesive at buried polymer interface studied by molecular dynamics simulation and sum frequency generation vibrational spectroscopy

Silicones have excellent material properties and are used extensively in many applications, ranging from adhesives and lubricants to electrical insulation. To ensure strong adhesion of silicone adhesives to a wide variety of substrates, silane-based adhesion promotors are typically blended into the silicone adhesive formulation. However, little is known at the molecular level about the true silane adhesion promotion mechanism, which limits the ability to develop even more effective adhesion promoters. To understand the adhesion promotion mechanism of silane molecules at the molecular level, this study has used sum frequency generation vibrational spectroscopy (SFG) to determine the behavior of (3-glycidoxypropyl)trimethoxy silane (γ-GPS) at the buried interface between poly(ethylene terephthalate) (PET) and a bulk silicone adhesive. To complement and extend the SFG results, atomistic molecular dynamics (MD) simulations were applied to investigate molecular behavior and interfacial interaction of γ-GPS at the silicone/PET interface. Free energy computations were used to study the γ-GPS interaction in the sample system and determine the γ-GPS interfacial segregation mechanism. Both experiments and simulations consistently show that γ-GPS molecules prefer to segregate at the interface between PET and PDMS. The methoxy groups on γ-GPS molecules orient toward the PDMS polymer phase. The consistent picture of interfacial structure emerging from both simulation and experiment provides enhanced insight on how γ-GPS behaves in the silicone - PET system and illustrates why γ-GPS could improve the adhesion of silicone adhesive, leading to further understanding of silicone adhesion mechanisms useful in the design of silicone adhesives with improved performance.

Droplet Microfluidics Powered Hydrogel Microparticles for Stem Cell-Mediated Biomedical Applications

Stem cell-related therapeutic technologies have garnered significant attention of the research community for their multi-faceted applications. To promote the therapeutic effects of stem cells, the strategies for cell microencapsulation in hydrogel microparticles have been widely explored, as the hydrogel microparticles have the potential to facilitate oxygen diffusion and nutrient transport alongside their ability to promote crucial cell-cell and cell-matrix interactions. Despite their significant promise, there is an acute shortage of automated, standardized, and reproducible platforms to further stem cell-related research. Microfluidics offers an intriguing platform to produce stem cell-laden hydrogel microparticles (SCHMs) owing to its ability to manipulate the fluids at the micrometer scale as well as precisely control the structure and composition of microparticles. In this review, the typical biomaterials and crosslinking methods for microfluidic encapsulation of stem cells as well as the progress in droplet-based microfluidics for the fabrication of SCHMs are outlined. Moreover, the important biomedical applications of SCHMs are highlighted, including regenerative medicine, tissue engineering, scale-up production of stem cells, and microenvironmental simulation for fundamental cell studies. Overall, microfluidics holds tremendous potential for enabling the production of diverse hydrogel microparticles and is worthy for various stem cell-related biomedical applications.

Photoacoustic: A Versatile Nongenetic Method for High-Precision Neuromodulation

High-precision neuromodulation plays a pivotal role in elucidating fundamental principles of neuroscience and treating specific neurological disorders. Optical neuromodulation, enabled by spatial resolution defined by the diffraction limit at the submicrometer scale, is a general strategy to achieve such precision. Optogenetics offers single-neuron spatial resolution with cellular specificity, whereas the requirement of genetic transfection hinders its clinical application. Direct photothermal modulation, an alternative nongenetic optical approach, often associates a large temperature increase with the risk of thermal damage to surrounding tissues.Photoacoustic (also called optoacoustic) neural stimulation is an emerging technology for neural stimulation with the following key features demonstrated. First, the photoacoustic approach demonstrated high efficacy without the need for genetic modification. The generated pulsed ultrasound upon ns laser pulses with energy ranging from a few μJ to tens of μJ is sufficient to activate wild-type neurons. Second, the photoacoustic approach provides sub-100-μm spatial precision. It overcomes the fundamental wave diffraction limit of ultrasound by harnessing the localized ultrasound field generated through light absorption. A spatial precision of 400 μm has been achieved in rodent brains using a fiber-based photoacoustic emitter. Single-cell stimulation in neuronal cultures in vitro and in brain slices ex vivo is achieved using tapered fiber-based photoacoustic emitters. This precision is 10 to 100 times better than that for piezo-based low-frequency ultrasound and is essential to pinpoint a specific region or cell population in a living brain. Third, compared to direct photothermal stimulation via temperature increase, photoacoustic stimulation requires 40 times less laser energy dose to evoke neuron activities and is associated with a minimal temperature increase of less than 1 °C, preventing potential thermal damage to neurons. Fourth, photoacoustics is a versatile approach and can be designed in various platforms aiming at specific applications. Our team has shown the design of fiber-based photoacoustic emitters, photoacoustic nanotransducers, soft biocompatible photoacoustic films, and soft photoacoustic lenses. Since they interact with neurons through ultrasound without the need for direct contact, photoacoustic enables noninvasive transcranial and dura-penetrating brain stimulation without compromising high precision.In this Account, we will first review the basic principles of photoacoustic and discuss the key design elements of PA transducers for neural modulation guided by the principle. We will also highlight how these design goals were achieved from a materials chemistry perspective. The design of different PA interfaces, their unique capability, and their applications in neural systems will be reviewed. In the end, we will discuss the remaining challenges and future perspectives for this technology.

Merging σ-Bond Metathesis with Polymerization Catalysis: Insights into Rare-Earth Metal Complexes, End-Group Functionalization, and Application Prospects

Polymers with well-defined structures, synthesized through metal-catalyzed processes, and having end groups exhibiting different polarity and reactivity than the backbone, are gaining considerable attention in both scientific and industrial communities. These polymers show potential applications as fundamental building blocks and additives in the creation of innovative functional materials. Investigations are directed toward identifying the most optimal and uncomplicated synthetic approach by employing a combination of living coordination polymerization mediated by rare-earth metal complexes and C-H bond activation reaction by σ-bond metathesis. This combination directly yields catalysts with diverse functional groups from a single precursor, enabling the production of terminal-functionalized polymers without the need for sequential reactions, such as termination reactions. The utilization of this innovative methodology allows for precise control over end-group functionalities, providing a versatile approach to tailor the properties and applications of the resulting polymers. This perspective discusses the principles, challenges, and potential advancements associated with this synthetic strategy, highlighting its significance in advancing the interface of metalorganic chemistry, polymer chemistry, and materials science.

Fast-Crosslinking Enabled Self-Roughed Polydimethylsiloxane Transparent Superhydrophobic Coating and Its Application in Anti-Liquid-Interference Electrothermal Device

Polydimethylsiloxane (PDMS)-based transparent and superhydrophobic coatings have important applications, such as anti-icing, corrosion resistance, self-cleaning, etc. However, their applications are limited by the inevitable introduction of nanoparticles/high-temperature/segmented PDMS to facilitate a raspy surface. In this study, a self-roughed, neat PDMS superhydrophobic coating with high transparency is developed via a one-step spray-coating technique. PDMS suspensions with various droplet sizes are synthesized and used as building blocks for raspy surface formation by controlled curing on the warm substrate. The optimal coating exhibits a large water contact angle of 155.4° and transparency (T550 = 82.3%). Meanwhile, the employed spray-coating technique is applicable to modify a plethora of substrates. For proof-of-concept demonstrations, the use of the PDMS hydrophobic coating for anti-liquid-interference electrothermal devices and further transparent observation window for long-term operation in a sub-zero environment is shown successful. The proposed facile synthesis method of hydrophobic PDMS coating is expected to have great potential for a broad range of applications in the large-scale fabrication of fluorine-free, eco-friendly superhydrophobic surfaces.

Large-area, self-healing block copolymer membranes for energy conversion

Membranes are widely used for separation processes in applications such as water desalination, batteries and dialysis, and are crucial in key sectors of our economy and society1. The majority of technologically exploited membranes are based on solid polymers and function as passive barriers, whose transport characteristics are governed by their chemical composition and nanostructure. Although such membranes are ubiquitous, it has proved challenging to maximize selectivity and permeability independently, leading to trade-offs between these pertinent characteristics2. Self-assembled biological membranes, in which barrier and transport functions are decoupled3,4, provide the inspiration to address this problem5,6. Here we introduce a self-assembly strategy that uses the interface of an aqueous two-phase system to template and stabilize molecularly thin (approximately 35 nm) biomimetic block copolymer bilayers of scalable area that can exceed 10 cm2 without defects. These membranes are self-healing, and their barrier function against the passage of ions (specific resistance of approximately 1 MΩ cm2) approaches that of phospholipid membranes. The fluidity of these membranes enables straightforward functionalization with molecular carriers that shuttle potassium ions down a concentration gradient with exquisite selectivity over sodium ions. This ion selectivity enables the generation of electric power from equimolar solutions of NaCl and KCl in devices that mimic the electric organ of electric rays.

A Review of Methods to Modify the PDMS Surface Wettability and Their Applications

Polydimethylsiloxane (PDMS) has attracted great attention in various fields due to its excellent properties, but its inherent hydrophobicity presents challenges in many applications that require controlled wettability. The purpose of this review is to provide a comprehensive overview of some key strategies for modifying the wettability of PDMS surfaces by providing the main traditional methods for this modification and the results of altering the contact angle and other characteristics associated with this property. Four main technologies are discussed, namely, oxygen plasma treatment, surfactant addition, UV-ozone treatment, and the incorporation of nanomaterials, as these traditional methods are commonly selected due to the greater availability of information, their lower complexity compared to the new techniques, and the lower cost associated with them. Oxygen plasma treatment is a widely used method for improving the hydrophilicity of PDMS surfaces by introducing polar functional groups through oxidation reactions. The addition of surfactants provides a versatile method for altering the wettability of PDMS, where the selection and concentration of the surfactant play an important role in achieving the desired surface properties. UV-ozone treatment is an effective method for increasing the surface energy of PDMS, inducing oxidation, and generating hydrophilic functional groups. Furthermore, the incorporation of nanomaterials into PDMS matrices represents a promising route for modifying wettability, providing adjustable surface properties through controlled dispersion and interfacial interactions. The synergistic effect of nanomaterials, such as nanoparticles and nanotubes, helps to improve wetting behaviour and surface energy. The present review discusses recent advances of each technique and highlights their underlying mechanisms, advantages, and limitations. Additionally, promising trends and future prospects for surface modification of PDMS are discussed, and the importance of tailoring wettability for applications ranging from microfluidics to biomedical devices is highlighted. Traditional methods are often chosen to modify the wettability of the PDMS surface because they have more information available in the literature, are less complex than new techniques, and are also less expensive.

Polydimethylsiloxane Surface Modification of Microfluidic Devices for Blood Plasma Separation

Over the last decade, researchers have developed a variety of new analytical and clinical diagnostic devices. These devices are predominantly based on microfluidic technologies, where biological samples can be processed and manipulated for the collection and detection of important biomolecules. Polydimethylsiloxane (PDMS) is the most commonly used material in the fabrication of these microfluidic devices. However, it has a hydrophobic nature (contact angle with water of 110°), leading to poor wetting behavior and issues related to the mixing of fluids, difficulties in obtaining uniform coatings, and reduced efficiency in processes such as plasma separation and molecule detection (protein adsorption). This work aimed to consider the fabrication aspects of PDMS microfluidic devices for biological applications, such as surface modification methods. Therefore, we studied and characterized two methods for obtaining hydrophilic PDMS surfaces: surface modification by bulk mixture and the surface immersion method. To modify the PDMS surface properties, three different surfactants were used in both methods (Pluronic® F127, polyethylene glycol (PEG), and polyethylene oxide (PEO)) at different percentages. Water contact angle (WCA) measurements were performed to evaluate the surface wettability. Additionally, capillary flow studies were performed with microchannel molds, which were produced using stereolithography combined with PDMS double casting and replica molding procedures. A PDMS microfluidic device for blood plasma separation was also fabricated by soft lithography with PDMS modified by PEO surfactant at 2.5% (v/v), which proved to be the best method for making the PDMS hydrophilic, as the WCA was lower than 50° for several days without compromising the PDMS's optical properties. Thus, this study indicates that PDMS surface modification shows great potential for enhancing blood plasma separation efficiency in microfluidic devices, as it facilitates fluid flow, reduces cell aggregations and the trapping of air bubbles, and achieves higher levels of sample purity.

Preparation of Polyaniline-Modified Cellulose/PDMS Composite Triboelectric Material and Application of Its Pretreatment in MOW Pulp

Self-powered electronic equipment has rapidly developed in the fields of sensing, motion monitoring, and energy collection, posing a greater challenge to triboelectric materials. Triboelectric materials need to enhance their electrical conductivity and mechanical strength to address the increasing demand for stability and to mitigate unpredictable physical damage. In this study, polyaniline-modified cellulose was prepared by means of in situ polymerization and compounded with polydimethylsiloxane, resulting in a triboelectric material with enhanced strength and conductivity. The material was fabricated into a tubular triboelectric nanogenerator (TENG) (G-TENG), and an electrocatalytic pretreatment of mixed office waste paper (MOW) pulp was performed using papermaking white water as the flowing liquid to improve the deinking performance. The electrical output performance of G-TENG is highest at a flow rate of 400 mL/min, producing a voltage of 22.76 V and a current of 1.024 μA. Moreover, the deinking effect of MOW was enhanced after the electrical pretreatment. This study explores the potential application of G-TENG as a self-powered sensor power supply and emphasizes its prospect as an energy collection device.

Characterization of Buried Interfaces of Silicone Materials in Situ to Understand Their Fouling-Release, Antifouling, and Adhesion Properties

Poly(dimethylsiloxane) (PDMS) has numerous excellent properties and is extensively used as the main component of many silicone products in a variety of research fields and practical applications such as biomedical materials, aviation, construction, electronic devices, and automobiles. Interfacial structures of PDMS and other components in silicone systems are important for such research and applications. It is difficult to probe interfacial molecular structures of buried solid-liquid and solid-solid interfaces of silicone materials due to the lack of appropriate analytical tools. In this feature article, we presented our research on elucidating the molecular structures of PDMS as well as other additives in silicone samples at buried interfaces in situ at the molecular level using a nonlinear optical spectroscopic technique, sum frequency generation (SFG) vibrational spectroscopy. SFG was applied to study various PDMS surfaces in liquid environments to understand their fouling-release and antifouling activities. SFG has also been used to study buried solid-solid interfaces between silicone adhesives and polymers, elucidating the molecular adhesion mechanisms. Our SFG studies provide important knowledge on interfacial structure-function relationships of silicone materials, helping the design and development of silicone materials with improved properties through optimization of silicone interfacial structures.

Frequency dependence of nanorod self-alignment using microfluidic methods

Dielectrophoresis is a potential candidate for aligning nanorods on electrodes, in which the interplay between electric fields and microfluidics is critically associated with its yield. Despite much of previous work on dielectrophoresis, the impact of frequency modulation on dielectrophoresis-driven nanorod self-assembly is insufficiently understood. In this work, we systematically explore the frequency dependence of the self-alignment of silicon nanorod using a microfluidic channel. We vary the frequency from 1kHz to 1000 kHz and analyze the resulting alignments in conjunction with numerical analysis. Our experiment reveals an optimal alignment yield at approximately 100 kHz, followed by a decrease in alignment efficiency. The nanorod self-alignments are influenced by multiple consequences, including the trapping effect, induced electrical double layer, electrohydrodynamic flow, and particle detachment. This study provides insights into the impact of frequency modulation of electric fields on the alignment of silicon nanorods using dielectrophoresis, broadening its use in various future nanotechnology applications.

Advancements in Soft Robotics: A Comprehensive Review on Actuation Methods, Materials, and Applications

The flexibility and adaptability of soft robots enable them to perform various tasks in changing environments, such as flower picking, fruit harvesting, in vivo targeted treatment, and information feedback. However, these fulfilled functions are discrepant, based on the varied working environments, driving methods, and materials. To further understand the working principle and research emphasis of soft robots, this paper summarized the current research status of soft robots from the aspects of actuating methods (e.g., humidity, temperature, PH, electricity, pressure, magnetic field, light, biological, and hybrid drive), materials (like hydrogels, shape-memory materials, and other flexible materials) and application areas (camouflage, medical devices, electrical equipment, and grippers, etc.). Finally, we provided some opinions on the technical difficulties and challenges of soft robots to comprehensively comprehend soft robots, lucubrate their applications, and improve the quality of our lives.

Recent developments and future perspectives of microfluidics and smart technologies in wearable devices

Wearable devices are gaining popularity in the fields of health monitoring, diagnosis, and drug delivery. Recent advances in wearable technology have enabled real-time analysis of biofluids such as sweat, interstitial fluid, tears, saliva, wound fluid, and urine. The integration of microfluidics and emerging smart technologies, such as artificial intelligence (AI), machine learning (ML), and Internet of Things (IoT), into wearable devices offers great potential for accurate and non-invasive monitoring and diagnosis. This paper provides an overview of current trends and developments in microfluidics and smart technologies in wearable devices for analyzing body fluids. The paper discusses common microfluidic technologies in wearable devices and the challenges associated with analyzing each type of biofluid. The paper emphasizes the importance of combining smart technologies with microfluidics in wearable devices, and how they can aid diagnosis and therapy. Finally, the paper covers recent applications, trends, and future developments in the context of intelligent microfluidic wearable devices.

Resveratrol-Loaded Polydimethylsiloxane-Silica Hybrid Materials: Synthesis, Characterization, and Antitumoral Activity

In this work, hybrid materials within the polydimethylsiloxane-silica (PDMS-SiO2) system, synthesized via the sol-gel method, were developed and characterized for their potential to incorporate and release the bioactive compound resveratrol (RES). RES was incorporated into the materials with a high loading efficiency (>75%) using the rotary evaporator technique. This incorporation induced the amorphization of RES, resulting in enhanced solubility and in vitro release when compared to the free polyphenolic compound. The release profiles displayed pH dependence, exhibiting notably faster release at pH 5.2 compared to pH 7.4. The gradual release of RES over time demonstrated an initial time lag of approximately 4 h, being well described by the Weibull model. In vitro cytotoxicity studies were conducted on human osteosarcoma cells (MG-63), revealing a concentration-dependent decrease in cell viability for RES-loaded samples (for concentrations >50 µg mL-1).

Inkjet Printing of Pharmaceuticals

Inkjet printing (IJP) is an additive manufacturing process that selectively deposits ink materials, layer-by-layer, to create 3D objects or 2D patterns with precise control over their structure and composition. This technology has emerged as an attractive and versatile approach to address the ever-evolving demands of personalized medicine in the healthcare industry. Although originally developed for nonhealthcare applications, IJP harnesses the potential of pharma-inks, which are meticulously formulated inks containing drugs and pharmaceutical excipients. Delving into the formulation and components of pharma-inks, the key to precise and adaptable material deposition enabled by IJP is unraveled. The review extends its focus to substrate materials, including paper, films, foams, lenses, and 3D-printed materials, showcasing their diverse advantages, while exploring a wide spectrum of therapeutic applications. Additionally, the potential benefits of hardware and software improvements, along with artificial intelligence integration, are discussed to enhance IJP's precision and efficiency. Embracing these advancements, IJP holds immense potential to reshape traditional medicine manufacturing processes, ushering in an era of medical precision. However, further exploration and optimization are needed to fully utilize IJP's healthcare capabilities. As researchers push the boundaries of IJP, the vision of patient-specific treatment is on the horizon of becoming a tangible reality.

PDMS diaphragm based miniature fiber-optic Fabry-Perot dynamic pressure sensor for turbomachinery application

Small-sized, highly sensitive dynamic pressure sensors are crucial in the field of turbomachinery application. In this paper, a fiber-tip structure dynamic pressure sensor utilizing a small piece of glass tube as the air cavity and PDMS material as the diaphragm was fabricated. It has the advantage of being small in size with the diameter of 125 µm while having high sensitivity of 26.26 pm/kPa. The fabrication process was described in detail, which is simple and cost-effective. The sensor characteristics were studied theoretically and experimentally. Quasi-square pressure signal of different frequencies generated by the siren disk were measured by the sensor and compared with that obtained from the commercial piezoresistive pressure sensor to verify the accuracy of the proposed sensor. The R2 of the four pairs of pressure waveforms were 0.94, 0.81, 0.93, and 0.96, respectively. Stability testing of the sensor was also performed, showing that the sensor can work reliably under dynamic pressure environment.

Planar Polymer Membranes Accommodate Functional Self-Assembly of Inserted Resorcinarene Nanocapsules

Solid-supported polymer membranes (SSPMs) offer great potential in material and life sciences due to their increased mechanical stability and robustness compared to solid-supported lipid membranes. However, there is still a need for expanding the functionality of SSPMs by combining them with synthetic molecular assemblies. In this study, SSPMs served as a flexible matrix for the insertion of resorcinarene monomers and their self-assembly into functional hexameric resorcinarene capsules. Resorcinarene capsules provide a large cavity with affinity specifically for cationic and polyhydroxylated molecules. While the capsules are stable in apolar organic solvents, they disassemble when placed in polar solvents, which limits their application. Here, a solvent-assisted approach was used for copolymer membrane deposition on solid support and simultaneous insertion of the resorcinarene monomers. By investigation of the molecular factors and conditions supporting the codeposition of the copolymer and resorcinarene monomers, a stable hybrid membrane was formed. The hydrophobic domain of the membrane played a crucial role by providing a sufficiently thick and apolar layer, allowing for the self-assembly of the capsules. The capsules were functional inside the membranes by encapsulating cationic guests from the aqueous environment. The amount of resorcinarene capsules in the hybrid membranes was quantified by a combination of quartz-crystal microbalance with dissipation and liquid chromatography-mass spectrometry, while the membrane topography and layer composition were analyzed by atomic force microscopy and neutron reflectometry. Functional resorcinarene capsules inside SSPMs can serve as dynamic sensors and potentially as cross-membrane transporters, thus holding great promise for the development of smart surfaces.

Transparent PDMS Surfaces with Covalently Attached Lubricants for Enhanced Anti-adhesion Performance

Liquid-like surfaces featuring slippery, omniphobic, covalently attached liquids (SOCALs) reduce unwanted adhesion by providing a molecularly smooth and slippery surface arising from the high mobility of the liquid chains. Such SOCALs are commonly prepared on hard substrates, such as glass, wafers, or metal oxides, despite the importance of nonpolar elastomeric substrates, such as polydimethylsiloxane (PDMS) in anti-fouling or nonstick applications. Compared to polar elastomers, hydrophobic PDMS elastomer activation and covalent functionalization are significantly more challenging, as PDMS tends to display fast hydrophobic recovery upon activation as well as superficial cracking. Through the extraction of excess PDMS oligomers and fine-tuning of plasma activation parameters, homogeneously functionalized PDMS with fluorinated polysiloxane brushes could be obtained while at the same time reducing crack formation. Polymer brush mobility was increased through the addition of a smaller molecular silane linker to exhibit enhanced dewetting properties and reduced substrate swelling compared to functionalizations featuring hydrocarbon functionalities. Linear polymer brushes were verified by thermogravimetric analysis. The optical properties of PDMS remained unaffected by the activation in high-frequency plasma but were impacted by low-frequency plasma. Drastic decreases in solid adhesion of not just complex contaminants but even ice could be shown in horizontal push tests, demonstrating the potential of SOCAL-functionalized PDMS surfaces for improved nonstick applications.

Plasma-Activated Polydimethylsiloxane Microstructured Pattern with Collagen for Improved Myoblast Cell Guidance

We focused on polydimethylsiloxane (PDMS) as a substrate for replication, micropatterning, and construction of biologically active surfaces. The novelty of this study is based on the combination of the argon plasma exposure of a micropatterned PDMS scaffold, where the plasma served as a strong tool for subsequent grafting of collagen coatings and their application as cell growth scaffolds, where the standard was significantly exceeded. As part of the scaffold design, templates with a patterned microstructure of different dimensions (50 × 50, 50 × 20, and 30 × 30 μm2) were created by photolithography followed by pattern replication on a PDMS polymer substrate. Subsequently, the prepared microstructured PDMS replicas were coated with a type I collagen layer. The sample preparation was followed by the characterization of material surface properties using various analytical techniques, including scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). To evaluate the biocompatibility of the produced samples, we conducted studies on the interactions between selected polymer replicas and micro- and nanostructures and mammalian cells. Specifically, we utilized mouse myoblasts (C2C12), and our results demonstrate that we achieved excellent cell alignment in conjunction with the development of a cytocompatible surface. Consequently, the outcomes of this research contribute to an enhanced comprehension of surface properties and interactions between structured polymers and mammalian cells. The use of periodic microstructures has the potential to advance the creation of novel materials and scaffolds in tissue engineering. These materials exhibit exceptional biocompatibility and possess the capacity to promote cell adhesion and growth.

Revolutionizing targeting precision: microfluidics-enabled smart microcapsules for tailored delivery and controlled release

As promising delivery systems, smart microcapsules have garnered significant attention owing to their targeted delivery loaded with diverse active materials. By precisely manipulating fluids on the micrometer scale, microfluidic has emerged as a powerful tool for tailoring delivery systems based on potential applications. The desirable characteristics of smart microcapsules are associated with encapsulation capacity, targeted delivery capability, and controlled release of encapsulants. In this review, we briefly describe the principles of droplet-based microfluidics for smart microcapsules. Subsequently, we summarize smart microcapsules as delivery systems for efficient encapsulation and focus on target delivery patterns, including passive targets, active targets, and microfluidics-assisted targets. Additionally, based on release mechanisms, we review controlled release modes adjusted by smart membranes and on/off gates. Finally, we discuss existing challenges and potential implications associated with smart microcapsules.

Enhancement of the mechanical properties in ultra-low weight SWCNT sandwiched PDMS composites using a novel stacked architecture

This study focuses on enhancing the mechanical properties of thin, soft, free-standing films via a layer-by-layer (LBL) fabrication process called LBL-FP. Soft polymer nanocomposite (PNC) thin films, combining polydimethylsiloxane (PDMS) and single-walled carbon nanotubes (SWCNT) at ultra-low loadings using a unique bottom-up LBL-FP, are examined. Two different structures of layered composites, (i) LBL PNCs- Layered composites with alternating layers of PDMS and SWCNT, (ii) Bulk PNCs- Layered composites with SWCNT dispersed in the bulk of PDMS, are comparatively investigated for their structural and mechanical properties. Silane-functionalized SWCNT strengthens the chemical bonding with PDMS, improving adhesion and dispersion. Mechanical analysis using nanoindentation, delamination, and dynamic analysis highlights the advantages of LBL PNCs with alternating layers of PDMS and SWCNT. Notably, LBL PNC (0.5 wt%) exhibits significant improvements, such as 2.6X increased nanoindentation resistance, 3X improved viscoelasticity, and (2-5)X enhanced tensile properties in comparison with neat PDMS. Due to this, LBL PNCs offer potential for soft, lightweight applications like wearables, electromagnetic interference shielding materials, and strain sensors while advancing composite thin film mechanics. The study emphasizes using a stacked architecture to produce PDMS-SWCNT multilayered PNCs with improved mechanics utilizing ultra-low concentrations of SWCNT. This first-of-its-kind stack design facilitates possibilities for lightweight composites utilizing less fillers. The LBL assembly involves the stacking of alternating layers of different materials, each contributing specific properties to enhance the overall strength and toughness of the structure.

Performance-Enhanced Flexible Self-Powered Tactile Sensor Arrays Based on Lotus Root-Derived Porous Carbon for Real-Time Human-Machine Interaction of the Robotic Snake

Flexible tactile sensors play an important role in the development of wearable electronics and human-machine interaction (HMI) systems. However, poor sensing abilities, an indispensable external energy supply, and limited material selection have significantly constrained their advancement. Herein, a self-powered flexible triboelectric sensor (TES) is proposed by integrating lotus-root-derived porous carbon (PC) into polydimethylsiloxane (PDMS). Owing to the superior charge capturing capability of PC, the PDMS/PC (PPC)-based TES exhibits an open-circuit voltage (Voc) of 22.8 V when it is periodically patted by skin at the pressure of 2 N and the frequency of 1 Hz, which is 5 times higher than that of a pristine PDMS-based TES. Furthermore, the as-prepared self-powered TES exhibits a high sensitivity of 3.24 V kPa-1 below 15 kPa for detecting human motion signals, such as finger clicks, joint bends, etc. Last but not the least, after the assembly of a PPC-based TES array and construction of an HMI system, the robotic snake can be controlled remotely by recognizing finger touching signals. This work shows broad potential applications for the self-powered TES in the fields of intelligent robotics, flexible electronics, disaster relief, and intelligence spying.

Batch Fabrication of Microelectrode Arrays with Glassy Carbon Microelectrodes and Interconnections for Neurochemical Sensing: Promises and Challenges

Flexible multielectrode arrays with glassy carbon (GC) electrodes and metal interconnection (hybrid MEAs) have shown promising performance in multi-channel neurochemical sensing. A primary challenge faced by hybrid MEAs fabrication is the adhesion of the metal traces with the GC electrodes, as prolonged electrical and mechanical stimulation can lead to adhesion failure. Previous devices with GC electrodes and interconnects made of a homogeneous material (all GC) demonstrated exceptional electrochemical stability but required miniaturization for enhanced tissue integration and chronic electrochemical sensing. In this study, we used two different methods for the fabrication of all GC-MEAs on thin flexible substrates with miniaturized features. The first method, like that previously reported, involves a double pattern-transfer photolithographic process, including transfer-bonding on temporary polymeric support. The second method requires a double-etching process, which uses a 2 µm-thick low stress silicon nitride coating of the Si wafer as the bottom insulator layer for the MEAs, bypassing the pattern-transfer and demonstrating a novel technique with potential advantages. We confirmed the feasibility of the two fabrication processes by verifying the practical conductivity of 3 µm-wide 2 µm-thick GC traces, the GC microelectrode functionality, and their sensing capability for the detection of serotonin using fast scan cyclic voltammetry. Through the exchange and discussion of insights regarding the strengths and limitations of these microfabrication methods, our goal is to propel the advancement of GC-based MEAs for the next generation of neural interface devices.

Energy renormalization for temperature transferable coarse-graining of silicone polymer

The bottom-up prediction of thermodynamic and mechanical behaviors of polymeric materials based on molecular dynamics (MD) simulation is of critical importance in polymer physics. Although the atomistically informed coarse-grained (CG) model can access greater spatiotemporal scales and retain essential chemical specificity, the temperature-transferable CG model is still a big challenge and hinders widespread application of this technique. Herein, we use a silicone polymer, i.e., polydimethylsiloxane (PDMS), having an incredibly low chain rigidity as a model system, combined with an energy-renormalization (ER) approach, to systematically develop a temperature-transferable CG model. Specifically, by introducing temperature-dependent ER factors to renormalize the effective distance and cohesive energy parameters, the developed CG model faithfully preserved the dynamics, mechanical and conformational behaviors compared with the target all-atomistic (AA) model from glassy to melt regimes, which was further validated by experimental data. With the developed CG model featuring tremendously improved computational efficiency, we systematically explored the influences of cohesive interaction strength and temperature on the dynamical heterogeneity and mechanical response of polymers, where we observed consistent trends with other linear polymers with varying chain rigidity and monomeric structures. This study serves as an extension of our proposed ER approach of developing temperature transferable CG models with diverse segmental structures, highlighting the critical role of cohesive interaction strength on CG modeling of polymer dynamics and thermomechanical behaviors.

Reprogrammable Magnetic Soft Actuators with Microfluidic Functional Modules via Pixel-Assembly

Magnetic soft actuators and robots have attracted considerable attention in biomedical applications due to their speedy response, programmability, and biocompatibility. Despite recent advancements, the fabrication process of magnetic actuators and the reprogramming approach of their magnetization profiles continue to pose challenges. Here, a facile fabrication strategy is reported based on arrangements and distributions of reusable magnetic pixels on silicone substrates, allowing for various magnetic actuators with customizable architectures, arbitrary magnetization profiles, and integration of microfluidic technology. This approach enables intricate configurations with decent deformability and programmability, as well as biomimetic movements involving grasping, swimming, and wriggling in response to magnetic actuation. Moreover, microfluidic functional modules are integrated for various purposes, such as on/off valve control, curvature adjustment, fluid mixing, dynamic microfluidic architecture, and liquid delivery robot. The proposed method fulfills the requirements of low-cost, rapid, and simplified preparation of magnetic actuators, since it eliminates the need to sustain pre-defined deformations during the magnetization process or to employ laser heating or other stimulation for reprogramming the magnetization profile. Consequently, it is envisioned that magnetic actuators fabricated via pixel-assembly will have broad prospects in microfluidics and biomedical applications.

Functionalization of Polydimethylsiloxane with Diazirine-Based Linkers for Covalent Protein Immobilization

Biomolecule attachment to solid supports is critical for biomedical devices, such as biosensors and implants. Polydimethylsiloxane (PDMS) is commonly used for these applications due to its advantageous properties. To enhance the biomolecule immobilization on PDMS, a novel technique is demonstrated using newly synthesized diazirine molecules for the surface modification of PDMS. This nondestructive process involves a reaction between diazirine molecules and PDMS through C-H insertion with thermal or ultraviolet activation. The success of the PDMS modification is confirmed by various surface characterization techniques. Bovine serum albumin (BSA) and immunoglobulin G (IgG) are strongly attached to the modified PDMS surfaces, and the amount of protein is quantified using iodine-125 radiolabeling. The results demonstrate that PDMS is rapidly functionalized, and the stability of the immobilized proteins is significantly improved with multiple types of diazirine molecules and activation methods. Confocal microscopy provides three-dimensional images of the distribution of immobilized IgG on the surfaces and the penetration of diazirine-based linkers through the PDMS substrate during the coating process. Overall, this study presents a promising new approach for functionalizing PDMS surfaces to enhance biomolecule immobilization, and its potential applications can extend to multimaterial modifications for various diagnostic and medical applications such as microfluidic devices and immunoassays with relevant bioactive proteins.

Surface-segregating zwitterionic copolymers to control poly(dimethylsiloxane) surface chemistry

The use of microfluidic devices in biomedicine is growing rapidly in applications such as organs-on-chip and separations. Polydimethylsiloxane (PDMS) is the most popular material for microfluidics due to its ability to replicate features down to the nanoscale, flexibility, gas permeability, and low cost. However, the inherent hydrophobicity of PDMS leads to the adsorption of macromolecules and small molecules on device surfaces. This curtails its use in "organs-on-chip" and other applications. Current technologies to improve PDMS surface hydrophilicity and fouling resistance involve added processing steps or do not create surfaces that remain hydrophilic for long periods. This work describes a novel, simple, fast, and scalable method for improving surface hydrophilicity and preventing the nonspecific adsorption of proteins and small molecules on PDMS through the use of a surface-segregating zwitterionic copolymer as an additive that is blended in during manufacture. These highly branched copolymers spontaneously segregate to surfaces and rearrange in contact with aqueous solutions to resist nonspecific adsorption. We report that mixing a minute amount (0.025 wt%) of the zwitterionic copolymer in PDMS considerably reduces hydrophobicity and nonspecific adsorption of proteins (albumin and lysozyme) and small molecules (vitamin B12 and reactive red). PDMS blended with these zwitterionic copolymers retains its mechanical and physical properties for at least six months. Moreover, this approach is fully compatible with existing PDMS device manufacture protocols without additional processing steps and thus provides a low-cost and user-friendly approach to fabricating reliable biomicrofluidics.

Mechanisms underlying the influence of skin properties on a single cavitation bubble in low-frequency sonophoresis

As a safe and effective method for systemic transdermal drug delivery (TDD), sonophoresis has drawn much attention from researchers. Despite numerous studies confirming cavitation as the main reason for sonophoresis, the effect skin has on cavitation bubble dynamics remains elusive due to the difficulty of experimental challenges. For a start, we reveal how single cavitation bubble (SCB) dynamics are affected by skin properties, including elasticity, hydrophilicity and texture. We use polydimethylsiloxane (PDMS) to simulate human skin and record the temporary evolution of SCBs with synchronous ultrafast photography. The influences of skin properties on SCBs are concluded: 1) SCBs collapse later near walls with better elasticities and generate microjets with higher speed; 2) SCBs collapse later near hydrophilic walls with slower microjets; and 3) the existence of a texture structure on walls also delays the time of bubble collapse near them and slows the velocities of microjets (v) during collapses.

Application of positively charged red mud-based carriers for anaerobic ammonium oxidizing bacteria biofilm formation

Enrichment of anaerobic ammonium oxidizing bacteria (AnAOB) in the anaerobic ammonium oxidation (anammox) process remains a challenge in engineering applications. In this study, for faster enrichment of AnAOB, red mud-based carriers were positively charged with FeCl3 and microbial promoters. The experimental results showed that the average nitrogen removal rates of the red mud-based carriers (RMGA), FeCl3-modified red mud-based carriers (RMGA-Fe), and microbial promoter-modified red mud-based carriers (RMGA-MA) increased by 24.4%-175% compared with the commercially available K3 carriers. Combining the results of SEM and laser confocal microscope, electrostatic attraction played a leading role on loading AnAOB. The increase in the surface roughness and specific area of the carriers after the attachment and the presence of Fe2+, Ca2+, and Mg2+ plasma were necessary for the subsequent growth of AnAOB, while the leaching of Cr(VI) promoted the nitrogen removal effect of AnAOB.

Functional PDMS Elastomers: Bulk Composites, Surface Engineering, and Precision Fabrication

Polydimethylsiloxane (PDMS)-the simplest and most common silicone compound-exemplifies the central characteristics of its class and has attracted tremendous research attention. The development of PDMS-based materials is a vivid reflection of the modern industry. In recent years, PDMS has stood out as the material of choice for various emerging technologies. The rapid improvement in bulk modification strategies and multifunctional surfaces has enabled a whole new generation of PDMS-based materials and devices, facilitating, and even transforming enormous applications, including flexible electronics, superwetting surfaces, soft actuators, wearable and implantable sensors, biomedicals, and autonomous robotics. This paper reviews the latest advances in the field of PDMS-based functional materials, with a focus on the added functionality and their use as programmable materials for smart devices. Recent breakthroughs regarding instant crosslinking and additive manufacturing are featured, and exciting opportunities for future research are highlighted. This review provides a quick entrance to this rapidly evolving field and will help guide the rational design of next-generation soft materials and devices.

Hydrogel-Sheathed hiPSC-Derived Heart Microtissue Enables Anchor-Free Contractile Force Measurement

In vitro reconstruction of highly mature engineered heart tissues (EHTs) is attempted for the selection of cardiotoxic drugs suitable for individual patients before administration. Mechanical contractile force generated in the EHTs is known to be a critical indicator for evaluating the EHT response. However, measuring contractile force requires anchoring the EHT in a tailored force-sensing cell culture chamber, causing technical difficulties in the stable evaluation of contractile force in long-term culture. This paper proposes a hydrogel-sheathed human induced pluripotent stem cell (hiPSC)-derived heart microtissue (H3 M) that can provide an anchor-free contractile force measurement platform in commonly used multi-well plates. The contractile force associated with tissue formation and drug response is calculated by motion tracking and finite element analysis on the bending angle of the hydrogel sheath. From the experiment of the drug response, H3 M is an excellent drug screening platform with high sensitivity and early testing capability compared to conventionally anchored EHT. This unique platform would be useful and versatile for regenerative therapy and drug discovery research in EHT.

Stress Concentration on PDMS: An evaluation of three numerical constitutive models using digital image correlation

The examination of hyperelastic materials' behavior, such as polydimethylsiloxane (PDMS), is crucial for applications in areas as biomedicine and electronics. However, the limitations of hyperelastic models for specific stress scenarios, with stress concentration, are not well explored on the literature. To address this, firstly, three constitutive models were evaluated (Neo-Hookean, Mooney-Rivlin, and Ogden) using numerical simulations and Digital Image Correlation (DIC) analysis during a uniaxial tensile test. The samples were made of PDMS with stress concentration geometries (center holes, shoulder fillets, and edge notches). Results of ANOVA analysis showed that any of the three models can be chosen for numerical analysis of PDMS since no significant differences in suitability were found. Finally, the Ogen model was chosen to obtain the stress concentration factors for these geometries, a property which characterize how discontinuities change the maximum stress supported by an element. Our study provides new values for variables needed to analyze and design hyperelastic elements and produce a foundation for understanding PDMS stress-strain behavior.

Nanomaterials Solutions for Contraception: Concerns, Advances, and Prospects

Preventing unintentional pregnancy is one of the goals of a global public health policy to minimize effects on individuals, families, and society. Various contraceptive formulations with high effectiveness and acceptance, including intrauterine devices, hormonal patches for females, and condoms and vasectomy for males, have been developed and adopted over the last decades. However, distinct breakthroughs of contraceptive techniques have not yet been achieved, while the associated long-term adverse effects are insurmountable, such as endocrine system disorder along with hormone administration, invasive ligation, and slowly restored fertility after removal of intrauterine devices. Spurred by developments of nanomaterials and bionanotechnologies, advanced contraceptives could be fulfilled via nanomaterial solutions with much safer and more controllable and effective approaches to meet various and specific needs for women and men at different reproductive stages. Nanomedicine techniques have been extended to develop contraceptive methods, such as the targeted drug delivery and controlled release of hormone using nanocarriers for females and physical stimulation assisted vasectomy using functional nanomaterials via photothermal treatment or magnetic hyperthermia for males. Nanomaterial solutions for advanced contraceptives offer significantly improved biosafety, noninvasive administration, and controllable reversibility. This review summarizes the nanomaterial solutions to female and male contraceptives including the working mechanisms, clinical concerns, and their merits and demerits. This work also reviewed the nanomaterials that have been adopted in contraceptive applications. In addition, we further discuss safety considerations and future perspectives of nanomaterials in nanostrategy development for next-generation contraceptives. We expect that nanomaterials would potentially replace conventional materials for contraception in the near future.

Dimethylsilanediol from silicone elastomers: Analysis, release from biopharmaceutical process equipment, and clearance studies

Polysiloxanes are considered one of the most important commercial families of synthetic elastomers. They are frequently employed in biopharmaceutical manufacturing equipment as flexible single-use solutions due to superior material properties and compatibility with diverse sterilization methods. Extractables and leachables (E&L) testing is essential in qualifying such equipment, involving extraction studies to assess the potential release of compounds from plastic components for risk assessment. Silicone releases oligomeric siloxanes and small hydrolysis products, with dimethylsilanediol (DMSD) being the main hydrolysis product found in significant concentrations in aqueous process solutions. DMSD presents challenges for analysis, requiring specifically tailored analytical methods to detect it, which are commonly not applied in standard E&L screening tests. In biopharmaceutical manufacturing, it is relevant to consider the potential of DMSD to repolymerize into silicone oil when specific process parameters are altered. This may lead to interactions with drug ingredients, including proteins, resulting in the formation of aggregates. We synthesized and characterized DMSD using X-ray structure analysis and established an HPLC method with a refractive index detector to investigate the release of DMSD from commercially available silicone tubing used in drug manufacturing following autoclaving and irradiation. Subsequently, we assessed typical biopharmaceutical downstream operations for effectively removing this compound from the process stream.

Tunable thermoplastic elastomer gels derived from controlled-distribution triblock copolymers with crystallizable endblocks

Thermoplastic elastomers (TPEs), a commercially important category of triblock copolymers, are employed alone or upon physical modification with a midblock-selective oil (to form TPE gels, TPEGs) in a broad range of contemporary technologies. While most copolymers in this class of self-networking macromolecules possess glassy polystyrene endblocks and a rubbery polydiene or polyolefin midblock, we investigate TPEGs fabricated from a novel controlled-distribution copolymer with crystallizable polyolefin endblocks and a random-copolymer midblock. According to both electron microscopy and small-angle scattering, the morphologies of these TPEGs remain largely invariant up to 40 wt% oil and then transform considerably at higher oil levels. Although reductions in endblock melting point and crystallinity measured by thermal calorimetry accompany increasing oil content, mechanical properties such as the uniaxial strain at break and fracture toughness improve in some cases by over 50% between 5 and 40 wt% oil. In fact, the strain at break can reach 2500% within this range, thereby confirming that (i) the structure-property relationships of these unique TPEGs are highly composition-tunable and (ii) these TPEGs, stabilized by crystallizable endblocks, provide an attractive alternative for ultrasoft and stretchy recyclable materials.

A Rapid and Dual Optical CO2 -responsive Polydimethylsiloxane Elastomer with a Fluorinated Cyanine Dye

We found that our optically CO2 -responsive polydimethylsiloxane (PDMS) elastomer rapidly and reversibly underwent both visible and fluorescent color changes in the presence of CO2 gas. Unlike conventional optically CO2 -responsive polymeric materials, it functions in totally dry gaseous conditions. The visible color and fluorescence of the elastomer sheet change after only 1 min of exposure to CO2 , and the sheet exhibits excellent repeatability in terms of color switching that persists for at least 20 times.

Degradable Elastomeric Silk Biomaterial for Flexible Bioelectronics

The integration of degradable and biomimetic approaches in material and device development can facilitate the next generation of sustainable (bio) electronics. The use of functional degradable materials presents exciting opportunities for applications in healthcare, soft robotics, energy, and electronics. These include conformability to curved surfaces, matching of stiffness of tissue, and the ability to withstand mechanical deformations. Nature-derived materials such as silk fibroin (SF) provide excellent biocompatibility, resorbability, and tunable properties toward such goals. However, fibroin alone lacks the required mechanical properties and durability for processing in biointegrated electronics and dry conditions. To overcome these limitations, we report on an elastomeric photocurable composite of silk fibroin and poly(dimethylsiloxane) (PDMS). Photofibroin (containing methacryl functionalities) is doped with photoPDMS (methacryloxypropyl-terminated poly(dimethylsiloxane)) to form an elastomeric photofibroin (ePF) composite. The elastomeric silk is photocurable, allowing for microfabrication using UV photolithography. It is suitable for circuits, strain-sensing devices, and biointegrated systems. The ePF exhibits flexibility in both wet and dry conditions, enhanced mechanical strength and long-term durability, and optical transparency. It is stable at high temperatures, compatible with electronic materials, and cytocompatible while being enzymatically degradable. This work therefore highlights a path toward combining natural and synthetic materials to achieve versatile properties and demonstrates the potential of silk fibroin composites in (bio) electronics, encapsulation, and packaging.

Dual optofluidic distributed feedback dye lasers for multiplexed biosensing applications

Integrated optofluidic devices have become subjects of high interest for rapid biosensor devices due to their unique ability to combine the fluidic processing of small volumes of microfluidics with the analysis capabilities of photonic structures. By integrating dynamically reconfigurable optofluidic lasers on-chip, complex coupling can be eliminated while further increasing the capabilities of sensors to detect an increasing number of target biomarkers. Here, we report a polydimethylsiloxane-based device with two on-chip fluidic distributed feedback (DFB) laser cavities that are integrated with an orthogonal analyte channel for multiplexed fluorescence excitation. One DFB grating is filled with 4-(dicyanomethylene)-2-methyl-6-(4-dimethylaminostyryl)-4H-pyran dissolved in dimethyl sulfoxide. The second grating is filled with rhodamine 6G dissolved in a diluted ethylene glycol solution. We present characterization of both lasers through analysis of the lasing spectra for spectral narrowing along with a power series to observe threshold behavior. We then demonstrate simultaneous detection of two different fluorescent microbeads as a proof of concept for scalable, single biomarker analysis using on-chip optofluidic lasers.

Current Trends and Promising Electrode Materials in Micro-Supercapacitor Printing

The development of scientific and technological foundations for the creation of high-performance energy storage devices is becoming increasingly important due to the rapid development of microelectronics, including flexible and wearable microelectronics. Supercapacitors are indispensable devices for the power supply of systems requiring high power, high charging-discharging rates, cyclic stability, and long service life and a wide range of operating temperatures (from -40 to 70 °C). The use of printing technologies gives an opportunity to move the production of such devices to a new level due to the possibility of the automated formation of micro-supercapacitors (including flexible, stretchable, wearable) with the required type of geometric implementation, to reduce time and labour costs for their creation, and to expand the prospects of their commercialization and widespread use. Within the framework of this review, we have focused on the consideration of the key commonly used supercapacitor electrode materials and highlighted examples of their successful printing in the process of assembling miniature energy storage devices.

Bio-inspired microfluidics: A review

Biomicrofluidics, a subdomain of microfluidics, has been inspired by several ideas from nature. However, while the basic inspiration for the same may be drawn from the living world, the translation of all relevant essential functionalities to an artificially engineered framework does not remain trivial. Here, we review the recent progress in bio-inspired microfluidic systems via harnessing the integration of experimental and simulation tools delving into the interface of engineering and biology. Development of "on-chip" technologies as well as their multifarious applications is subsequently discussed, accompanying the relevant advancements in materials and fabrication technology. Pointers toward new directions in research, including an amalgamated fusion of data-driven modeling (such as artificial intelligence and machine learning) and physics-based paradigm, to come up with a human physiological replica on a synthetic bio-chip with due accounting of personalized features, are suggested. These are likely to facilitate physiologically replicating disease modeling on an artificially engineered biochip as well as advance drug development and screening in an expedited route with the minimization of animal and human trials.

Design of Intelligent Protective Composite Material with Stress Rate Sensitivity, Strong Interface Adhesion, and Recyclability

Poly(dimethyl siloxane) (PDMS) elastomers play a significant role in smart materials, actuators, and flexible electronics. However, current PDMS lacks adhesion abilities and intelligent responsive properties, which limit its further application. In this study, the polydimethylsiloxane-ureidopyrimidinone impact hardening polymer (PDMS-UI) composites are manufactured by a dual cross-linking compositing tactic. PDMS, a chemically stable cross-linked network, acts as a framework owing to its excellent mechanical strength, whereas UI, a reversible dynamic physically cross-linked network with quadruple hydrogen bonding, endows the PDMS-UI with excellent self-healing ability (efficiency > 90%) and energy absorption (75.23%). Impressively, owing to multivalent hydrogen bonds, the PDMS-UI exhibits superior adhesion performance: the adhesion strength on various substrates exceed 150 kPa and that on the Ferrum substrate reaches 570 kPa. These outstanding properties make the PDMS-UI a potential candidate for application in both well-developed fields, such as, wearable protective materials, artificial skin and soft robotics.

A Needle-Free Transdermal Patch for Sampling Interstitial Fluid

OBJECTIVE

Modern diagnostics is pivoting towards less invasive health monitoring in dermal interstitial fluid, rather than blood or urine. However, the skin's outermost layer, the stratum corneum, makes accessing the fluid more difficult without invasive, needle-based technology. Simple, minimally invasive means for surpassing this hurdle are needed.

METHODS

To address this problem, a flexible, Band-Aid-like patch for sampling interstitial fluid was developed and tested. This patch uses simple resistive heating elements to thermally porate the stratum corneum, allowing the fluid to exude from the deeper skin tissue without applying external pressure. Fluid is then transported to an on-patch reservoir through self-driving hydrophilic microfluidic channels.

RESULTS

Testing with living, ex-vivo human skin models demonstrated the device's ability to rapidly collect sufficient interstitial fluid for biomarker quantification. Further, finite-element modeling showed that the patch can porate the stratum corneum without raising the skin's temperature to pain-inducing levels in the nerve-laden dermis.

CONCLUSION

Relying only on simple, commercially scalable fabrication methods, this patch outperforms the collection rate of various microneedle-based patches, painlessly sampling a human bodily fluid without entering the body.

SIGNIFICANCE

The technology holds potential as a clinical device for an array of biomedical applications, especially with the integration of on-patch testing.

Polymeric and biological membranes for organ-on-a-chip devices

Membranes are fundamental elements within organ-on-a-chip (OOC) platforms, as they provide adherent cells with support, allow nutrients (and other relevant molecules) to permeate/exchange through membrane pores, and enable the delivery of mechanical or chemical stimuli. Through OOC platforms, physiological processes can be studied in vitro, whereas OOC membranes broaden knowledge of how mechanical and chemical cues affect cells and organs. OOCs with membranes are in vitro microfluidic models that are used to replace animal testing for various applications, such as drug discovery and disease modeling. In this review, the relevance of OOCs with membranes is discussed as well as their scaffold and actuation roles, properties (physical and material), and fabrication methods in different organ models. The purpose was to aid readers with membrane selection for the development of OOCs with specific applications in the fields of mechanistic, pathological, and drug testing studies. Mechanical stimulation from liquid flow and cyclic strain, as well as their effects on the cell's increased physiological relevance (IPR), are described in the first section. The review also contains methods to fabricate synthetic and ECM (extracellular matrix) protein membranes, their characteristics (e.g., thickness and porosity, which can be adjusted depending on the application, as shown in the graphical abstract), and the biological materials used for their coatings. The discussion section joins and describes the roles of membranes for different research purposes and their advantages and challenges.

Engineering of Siloxanes for Stabilizing Silicon Anode Materials

Silicon (Si) is considered the most promising anode material for the next generation of lithium-ion batteries (LIBs) because of its high theoretical specific capacity and abundant reserves. However, the volume expansion of silicon in the cycling process causes the destruction of the electrode structure and irreversible capacity loss. As a result, the commercial application of silicon materials is greatly hindered. In recent years, siloxane-based organosilicon materials have been widely used in silicon anode of LIBs because of their unique structure and physical and chemical properties, and have shown excellent electrochemical properties. The comprehensive achievement of siloxanes in silicon-based LIBs can be understood better through a systematic summary, which is necessary to guide the design of electrodes and achieve better electrochemical performance. This paper systematically introduces the unique advantages of siloxane materials in electrode, surface/interface modification, binder, and electrolyte. The challenges and future directions for siloxane materials are presented to enhance their performance and expand their application in silicon-based LIBs.

Zn(II)-Siloxane Clusters as Versatile Building Blocks for Carboxylate-Based Metal-Organic Frameworks

Siloxanes have long been known for their highly desirable properties suited for a wide range of practical applications; however, their utilization as modular building blocks for crystalline open frameworks has been limited. In this study, a simple solvothermal pathway has been found to synthesize unprecedented Zn(II)-siloxane clusters supported by acetate ligands, [(RSiO2)8Zn8(CH3CO2)8] (R = Me or Ph). The same reaction using a dicarboxylate ligand such as 1,4-benzenedicarboxylate or 2,6-naphthalenedicarboxylate produces a new type of metal-organic framework, named SiMOF here, based on the [Si8Zn8] units. With the maximum connectivity of 8, the building block is shown to form topologically interesting structures such as octahedral supercages or uninodal 8-connected frameworks. All SiMOFs synthesized possess permanent porosity and high thermal stability and are naturally hydrophobic, as demonstrated by adsorptions of toluene, ethanol, methanol, and water vapor as well as water contact angle measurements. These promising characteristics for well-defined porous solids are attributed to metal-bound siloxane groups in the structural building units.

Transparent Electronics for Wearable Electronics Application

Recent advancements in wearable electronics offer seamless integration with the human body for extracting various biophysical and biochemical information for real-time health monitoring, clinical diagnostics, and augmented reality. Enormous efforts have been dedicated to imparting stretchability/flexibility and softness to electronic devices through materials science and structural modifications that enable stable and comfortable integration of these devices with the curvilinear and soft human body. However, the optical properties of these devices are still in the early stages of consideration. By incorporating transparency, visual information from interfacing biological systems can be preserved and utilized for comprehensive clinical diagnosis with image analysis techniques. Additionally, transparency provides optical imperceptibility, alleviating reluctance to wear the device on exposed skin. This review discusses the recent advancement of transparent wearable electronics in a comprehensive way that includes materials, processing, devices, and applications. Materials for transparent wearable electronics are discussed regarding their characteristics, synthesis, and engineering strategies for property enhancements. We also examine bridging techniques for stable integration with the soft human body. Building blocks for wearable electronic systems, including sensors, energy devices, actuators, and displays, are discussed with their mechanisms and performances. Lastly, we summarize the potential applications and conclude with the remaining challenges and prospects.

Compact highly sensitive Fabry-Perot temperature and gas pressure sensing probe fabricated by a femtosecond laser and PDMS

A high sensitivity optical fiber temperature and gas pressure sensor with integrated micro-cavity is proposed. First, a single-mode optical fiber (SMF) is spliced with a section of capillary, and then the sensitive material polydimethylsiloxane (PDMS) is filled into the capillary to form a Fabry-Perot interferometer (FPI). Finally, a femtosecond laser is used to ablate the fiber core of the SMF to form the third reflecting surface, constituting two cascaded FPIs. When two FPIs have a similar free spectral range, a Vernier effect is produced. The temperature and gas pressure sensitivity of the sensor reached 14.41 nm/°C and 113.82 nm/MPa, respectively, after using the sensitive material and Vernier effect double sensitization technology. In addition, a fiber Bragg grating is cascaded with the sensor, which can realize the simultaneous measurement of temperature and gas pressure and eliminate cross-sensitivity.