Droplet Microarrays: From Surface Patterning to High-Throughput Applications

Advances in high-throughput screening approaches for biosurfactants: current trends, bottlenecks and perspectives

The market size of biosurfactants (BSs) has been expanding at an extremely fast pace due to their broad application scope. Therefore, the re-construction of cell factories with modified genomic and metabolic profiles for desired industrial performance has been an intriguing aspect. Typical mutagenesis approaches generate huge mutant libraries, whereas a battery of specific, robust, and cost-effective high-throughput screening (HTS) methods is requisite to screen target strains for desired phenotypes. So far, only a few specialized HTS assays have been developed for BSs that were successfully applied to obtain anticipated mutants. The most important milestones to reach, however, continue to be: specificity, sensitivity, throughput, and the potential for automation. Here, we discuss important colorimetric and fluorometric HTS approaches for possible intervention on automated HTS platforms. Moreover, we explain current bottlenecks in developing specialized HTS platforms for screening high-yielding producers and discuss possible perspectives for addressing such challenges.

Tailoring the Wettability of Bacterial Cellulose Magnetobots via the Assembly of In Situ Synthesized and Surfactant-Coated Magnetic Nanoparticles

This study showcases the possibility of tailoring the wettability of magnetic bacterial cellulose (m-BC) composites by the combined effect of in situ synthesized magnetic nanoparticles (MNPs) distribution and simultaneous oleic acid (OA) coating within the BC matrix. This combined effect of MNPs and OA resulted in m-BC composites exhibiting solvent-dependent and time-dependent surface-wetting behavior, which was not observed in either individual cases of BC that have been modified with OA or BC that has MNPs adsorbed on its fibers. This tailored wettability in m-BCs was achieved via varying the concentrations of iron precursors, which governed the arrangement and morphology of MNPs (uniformly or clustered) on the BC membrane, although the same fraction of MNPs was observed in both the m-BCs. Finally, we have achieved delayed water absorption in m-BC_x (synthesized in a comparatively lower precursor concentration) and no absorption of water in m-BC_4x (synthesized in a 4-times-higher precursor concentration). The m-BC_4x composite maintained its hydrophobic characteristics in diverse environments, ranging from highly acidic conditions (pH 1.2) to physiological environments at pH 4, 5.5, and 7.4. The MNP agglomerates on the BC nanofibers in the m-BC_4x composite were found to be instrumental in attaining a stable cyclic absorption performance with structural integrity. Additionally, the magnetic-inducing heat generation efficiency of the m-BCs can be extended for evaporating low-boiling-point solvents. The present study expands the frontiers of BC-based magnetic composites by emphasizing the assembly of surfactant-coated magnetic nanostructures in their responsiveness to polar/nonpolar liquids with stable performance even in complex scenarios.

Valved Microwell Array Platforms for Stepwise Liquid Dispensing

The fabrication of microarray chips and the precise dispensing of nanoliter to microliter liquids are fundamental for high-throughput parallel biochemical testing. Conventional microwells, typically featuring a uniform cross section, fill completely in a single operation, complicating the introduction of multiple reagents for stepwise and combinatorial analyses. To overcome this limitation, we developed an innovative valved microwell array. Using ultraviolet (UV)-curing resin three-dimensional (3D) printing, these multilayer configurations can be rapidly fabricated through direct template printing and polydimethylsiloxane (PDMS) casting. Each microwell incorporates a microvalve structure, truncating fluids within the upper metering well and allowing transfer to the bottom reservoir well under centrifugal force. Sequential operations enable the introduction of multiple reagents, facilitating orthogonal combinations for complex assays. We explored four types of valving methods: DeepWell, Expansion, Bottleneck, and Membrane valve, each offering varying degrees of design complexity, operational efficiency, robustness, and precision. These methods constitute a versatile toolkit to accommodate a broad spectrum of analytical requirements. Our innovative approach redefines microwell architecture, direct manufacturing techniques, and stepwise fluid dispensation in microarrays.

Improved Teflon lift-off for droplet microarray generation and single-cell separation on digital microfluidic chips

Droplet microarrays (DMAs) leveraging wettability differences are instrumental in digital immunoassays, single-cell analysis, and high-throughput screening. This study introduces an enhanced Teflon lift-off process to fabricate hydrophilic-hydrophobic patterns on a digital microfluidic (DMF) chip, thereby integrating DMAs with DMF technology. By employing DMF for droplet manipulation and utilizing wettability differences, the automated generation of high-throughput DMAs was achieved. The volume of the microdroplets ranged from picoliters to nanoliters. For droplets with a diameter of 150 μm, the array density reached up to 1282 cm-2. We systematically investigated the influence of various DMF parameters on the formation of DMAs and applied this technique to particle distribution, achieving a single-cell isolation rate of approximately 30%. We believe that this method will be a potent tool to enhance the capabilities of DMAs and DMF technology and extend their applicability across more fields.

Deriving Superhydrophobicity Directly and Solely from Molecules: A Facile and Emerging Approach

Nature-inspired superhydrophobic surfaces have gained significant attention due to their various potential applications. Artificial superhydrophobic surfaces were fabricated through co-optimization of topography and low-surface-energy chemistry. In the conventional approach, artificial superhydrophobic surfaces are developed through associating mostly polymer, metal, alloys, nanoparticles, microparticles, etc. and commonly encounter several challenges related to scalability, durability, and complex fabrication processes. In response to these challenges, molecule-based approaches have emerged as a promising alternative, providing several advantages such as prolonged shelf life of depositing solution, higher solvent compatibility, and a simple fabrication process. In this Perspective, we have provided a concise overview of traditional and molecule-based approaches to fabricating superhydrophobic surfaces, highlighting recent advancements and challenges. We have discussed various molecule-based strategies for tailoring water wettability, customizing mechanical properties, developing substrate-independent coatings, prolonging the shelf life of deposition solutions, and so on. Here, we have illustrated the potential of molecule-based approaches in overcoming existing limitations and its importance to diverse and prospective practical applications.

Heterogeneous Organohydrogel Toward Automated and Interference-Free Gradient Feeding of Drugs in Cell Screening

Cell-based microarrays are widely used in the fields of drug discovery and toxicology. Precise gradient generation and automated drug feeding are essential for high-throughput screening of live cells in tiny droplets. However, most existing technologies either require sophisticated robotic equipment or cause mechanical/physiological interference with cells. Here, a heterogeneous organohydrogel is presented for automated gradient drug feeding, while ensuring minimal interference with cells. The heterogeneous organohydrogel comprises three crucial components. The bottom surface can automatically generate gradients functioning as a gradient generator, the organohydrogel bulk allows unidirectional transport of drugs without backflow, and the top surface with hydrophilic arrays can firmly anchor the cell-based droplet array to evaluate the concentration-dependent bioeffects of drugs accurately. Such a unique structure enables universal screening of different cell types and drugs dissolved in different solvents, requiring neither additional accessories nor arduous drug functionalization. The heterogeneous organohydrogel with unprecedented automation and non-interference possesses the enormous potential to be a next-generation platform for drug screening.

A Droplet-Based Microfluidic Platform for High-Throughput Culturing of Yeast Cells in Various Conditions

Yeast plays a significant role in a variety of fields. In particular, it is extensively used as a model organism in genetics and cellular biology studies, and is employed in the production of vaccines, pharmaceuticals, and biofuels. Traditional "bulk"-based studies on yeast growth often overlook cellular variability, emphasizing the need for single-cell analysis. Micro-droplets, tiny liquid droplets with high surface-area-to-volume ratios, offer a promising platform for investigating single or a small number of cells, allowing precise control and monitoring of individual cell behaviors. Microfluidic devices, which facilitate the generation of micro-droplets, are advantageous due to their reduced volume requirements and ability to mimic in vivo micro-environments. This study introduces a custom-designed microfluidic device to encapsulate yeasts in micro-droplets under various conditions in a parallel manner. The results reveal that optimal glucose concentrations promoted yeast growth while cycloheximide and Cu2+ ions inhibited it. This platform enhances yeast cultivation strategies and holds potential for high-throughput single-cell investigations in more complex organisms.

A droplet robotic system enabled by electret-induced polarization on droplet

Robotics for scientific research are evolving from grasping macro-scale solid materials to directly actuating micro-scale liquid samples. However, current liquid actuation mechanisms often restrict operable liquid types or compromise the activity of biochemical samples by introducing interfering mediums. Here, we propose a robotic liquid handling system enabled by a novel droplet actuation mechanism, termed electret-induced polarization on droplet (EPD). EPD enables all-liquid actuation in principle and experimentally exhibits generality for actuating various inorganic/organic liquids with relative permittivity ranging from 2.25 to 84.2 and volume from 500 nL to 1 mL. Moreover, EPD is capable of actuating various biochemical samples without compromising their activities, including various body fluids, living cells, and proteins. A robotic system is also coupled with the EPD mechanism to enable full automation. EPD's high adaptability with liquid types and biochemical samples thus promotes the automation of liquid-based scientific experiments across multiple disciplines.

High-Throughput Miniaturized Synthesis of PROTAC-Like Molecules

The development of miniaturized high-throughput in situ screening platforms capable of handling the entire process of drug synthesis to final screening is essential for advancing drug discovery in the future. In this study, an approach based on combinatorial solid-phase synthesis, enabling the efficient synthesis of libraries of proteolysis targeting chimeras (PROTACs) in an array format is presented. This on-chip platform allows direct biological screening without the need for transfer steps.  UV-induced release of target molecules into individual droplets facilitates further on-chip experimentation. Utilizing a mitogen-activated protein kinase kinases (MEK1/2) degrader as a template, a series of 132 novel PROTAC-like molecules is synthesized using solid-phase Ugi reaction. These compounds are further characterized using various methods, including matrix-assisted laser desorption ionization mass spectrometry (MALDI-MS) imaging, while consuming only a few milligrams of starting materials in total. Furthermore, the feasibility of culturing cancer cells on the modified spots and quantifying the effect of MEK suppression is demonstrated. The miniaturized synthesis platform lays a foundation for high-throughput in situ biological screening of potent PROTACs for potential anticancer activity and offers the potential for accelerating the drug discovery process by integrating miniaturized synthesis and biological steps on the same array.

EZ-SPOTs: A simple and robust high-throughput liquid handling platform

Liquid handling is a fundamental capability for many scientific experiments. Previously, we introduced the Surface Patterned Omniphobic Tiles (SPOTs) platform, which enables manipulation of hundreds to thousands of independent experiments without costly equipment or excessive consumable expenses. However, the SPOTs platform requires a custom coating formulation and lacks robustness. To overcome these limitations, we introduce EZ-SPOTs. These devices can be created in an hour with common fabrication tools and just three components - glass, a hydrophobic coating, and acrylic. EZ-SPOTs preserve many of the SPOTs platform's strengths - ease of use, ability to handle a wide range of volumes, and scalability - and adopt a durable and abrasion resistant coating that enables multiple reuses of each device. Here, we describe the fabrication of EZ-SPOTs and showcase how its reusability allows antibiotic susceptibility testing of many isolates using a single device. These results quantitatively match current gold standard assays and the increased throughput provides substantially more information than standard approaches.

Stretchable and Sweat-Wicking Patch for Skin-Attached Colorimetric Analysis of Sweat Biomarkers

Stretchable sweat sensors are promising technology that can acquire biomolecular insights for health and fitness monitoring by intimate integration with the body. However, current sensors often require microfabricated microfluidic channels to control sweat flow during lab-on-body analysis, which makes effective and affordable sweat sampling a significant practical challenge. Here, we present stretchable and sweat-wicking patches that utilize bioinspired smart wettable membranes for the on-demand manipulation of sweat flow. In a scalable process, the membrane is created by stacking hydrophobic elastomer nanofibers onto soft microfoams with predefined two-dimensional superhydrophobic and superhydrophilic patterns. The engineered heterogeneous wettability distribution allows these porous membranes to achieve enhanced extraction and selective collection of sweat in embedded assays. Despite the simplified architecture, the color reactions between sweat and chemical indicators are inhibited from directly contacting the skin to achieve a largely improved operation safety. The sensing patches can simultaneously quantify pH, urea, and calcium in sweat through digital colorimetric analysis with smartphone images. The construction with all compliant materials renders these patches soft and stretchy to achieve conformal attachment to the skin. Successfully analyzing sweat compositions after physical exercises illustrates the practical suitability of these skin-attachable sensors for health tracking and point-of-care diagnosis.

Compact Micropatterned Chip Empowers Undisturbed and Programmable Drug Addition in High-Throughput Cell Screening

Simultaneously adding multiple drugs and other chemical reagents to individual droplets at specific time points presents a significant challenge, particularly when dealing with tiny droplets in high-throughput screening applications. In this study, a micropatterned polymer chip is developed as a miniaturized platform for light-induced programmable drug addition in cell-based screening. This chip incorporates a porous superhydrophobic polymer film with atom transfer radical polymerization reactivity, facilitating the efficient grafting of azobenzene methacrylate, a photoconformationally changeable group, onto the hydrophilic regions of polymer matrix at targeted locations and with precise densities. By employing light irradiation, the cyclodextrin-azobenzene host-guest complexes formed on the polymer chip can switch from an "associated" to a "dissociated" state, granting precise photochemical control over the supramolecular coding system and its surface patterning ability. Significantly, the exceptional spatial and temporal control offered by these chemical transitions empowers to utilize digital light processing systems for simultaneous regulation and release of cyclodextrin-bearing drugs across numerous droplets containing suspended or adhered cells. This approach minimizes mechanical disruption while achieving precise control over the timing of addition, dosage, and integration varieties of released drugs in high-throughput screening, all programmable to meet specific requirements.

Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

ANDeS: An automated nanoliter droplet selection and collection device

The Droplet Microarray (DMA) has emerged as a tool for high-throughput biological and chemical applications by enabling miniaturization and parallelization of experimental processes. Due to its ability to hold hundreds of nanoliter droplets, the DMA enables simple screening and analysis of samples such as cells and biomolecules. However, handling of nanoliter volumes poses a challenge, as manual recovery of nanoliter volumes is not feasible, and traditional laboratory equipment is not suited to work with such low volumes, and small array formats. To tackle this challenge, we developed the Automated Nanoliter Droplet Selection device (ANDeS), a robotic system for automated collection and transfer of nanoliter samples from DMA. ANDeS can automatically collect volumes from 50 to 350 nL from the flat surface of DMA with a movement accuracy of ±30 µm using fused silica capillaries. The system can automatically collect and transfer the droplets from DMA chip into other platforms, such as microtiter plates, conical tubes or another DMA. In addition, to ensure high throughput and multiple droplet collection, the uptake of multiple droplets within a single capillary, separated by air gaps to avoid mixing of the samples within the capillary, was optimized and demonstrated. This study shows the potential of ANDeS in laboratory applications by using it for the collection and transfer of biological samples, contained in nanoliter droplets, for subsequent analysis. The experimental results demonstrate the ability of ANDeS to increase the versatility of the DMA platform by allowing for automated retrieval of nanoliter samples from DMA, which was not possible manually on the level of individual droplets. Therefore, it widens the variety of analytical techniques that can be used for the analysis of content of individual droplets and experiments performed using DMA. Thus, ANDeS opens up opportunities to expand the development of miniaturized assays in such fields as cell screening, omics analysis and combinatorial chemistry.

Stretchable and Smart Wettable Sensing Patch with Guided Liquid Flow for Multiplexed in Situ Perspiration Analysis

Stretchable sweat sensors have become a personalized wearable platform for continuous, noninvasive health monitoring through conformal integration with the human body. Typically, these devices are coupled with soft microfluidic systems to control sweat flow during advanced analysis processes. However, the implementation of these soft microfluidic devices is limited by their high fabrication costs and the need for skin adhesives to block natural perspiration. To overcome these limitations, a stretchable and smart wettable patch has been proposed for multiplexed in situ perspiration analysis. The patch includes a porous membrane in the form of a patterned microfoam and a nanofiber layer laminate, which extracts sweat selectively from the skin and directs its continuous flow across the device. The integrated electrochemical sensor array measures multiple biomarkers simultaneously such as pH, K+, and Na+. The soft sensing patch comprises compliant materials and structures that allow deformability of up to 50% strain, which enables a stable and seamless interface with the curvilinear human body. During continuous physical exercise, the device has demonstrated a special operating mode by actively accumulating sweat from the skin for multiplex electrochemical analysis of biomarker profiles. The smart wettable membrane provides an affordable solution to address the sampling challenges of in situ perspiration analysis.

Characterization of Particle Transport and Deposition Due to Heterogeneous Dewetting on Low-Cost Inkjet-Printed Devices

This work investigates the deposition patterns left by evaporating particle-laden droplets on heterogeneous surfaces with spatially varying wettability. Spatial differences in receding contact angles give rise to scalloped-shaped contact lines. During evaporation, the contact line recedes in one location and remains pinned in another. This nonuniform contact line recession results in particle self-assembly above areas where the contact line remains pinned but not where it recedes. This behavior is fairly robust across a variety of particle sizes, concentrations, and device geometries. We hypothesize that particle self-assembly in these cases is due to the competition between particle diffusion and evaporative-driven advective flow. Diffusion appears to be more pronounced in regions where the contact line recedes, while advection appears to be more pronounced near the pinned portion of the contact line. As such, particles appear to diffuse away from receding areas and toward pinned areas, where advection transports them to the contact line. The distribution of particle deposition above the pinned regions was influenced by the particle size and the concentration of particles in the droplet. Similar to homogeneous surfaces, deposition was more prevalent at the pinned portion of the contact line for smaller particles and lower concentrations and more uniformly distributed across the entire pinned region for larger particles and higher concentrations. A better understanding of this process may be beneficial in a wide variety of particle separation applications, such as printing, cell patterning, biosensing, and anti-icing.

Designing of anisotropic gradient surfaces for directional liquid transport: Fundamentals, construction, and applications

Many biological surfaces are capable of transporting liquids in a directional manner without energy consumption. Inspired by nature, constructing asymmetric gradient surfaces to achieve desired droplet transport, such as a liquid diode, brings an incredibly valuable and promising area of research with a wide range of applications. Enabled by advances in nanotechnology and manufacturing techniques, biomimetics has emerged as a promising avenue for engineering various types of anisotropic material system. Over the past few decades, this approach has yielded significant progress in both fundamental understanding and practical applications. Theoretical studies revealed that the heterogeneous composition and topography mainly govern the wetting mechanisms and dynamics behavior of droplets, including the interdisciplinary aspects of materials, chemistry, and physics. In this review, we provide a concise overview of various biological surfaces that exhibit anisotropic droplet transport. We discussed the theoretical foundations and mechanisms of droplet motion on designed surfaces and reviewed recent research advances in droplet directional transport on designed plane surfaces and Janus membranes. Such liquid-diode materials yield diverse promising applications, involving droplet collection, liquid separation and delivery, functional textiles, and biomedical applications. We also discuss the recent challenges and ongoing approaches to enhance the functionality and application performance of anisotropic materials.

Spontaneous Separation of Immiscible Organic Droplets on Asymmetric Wedge Channels with Hierarchical Microchannels

Spontaneous separation of immiscible organic droplets has substantial research implications for environmental protection and resource regeneration. Compared to the widely explored separation of oil-water mixtures, there are fewer reports on separating mixed organic droplets on open surfaces due to the low surface tension differences. Efficient separation of mixed organic liquids by exploiting the rapid spontaneous transport of droplets on open surfaces remains a challenge. Here, through the fusion of inspiration from the fast droplet transport capability of Sarracenia trichome and the asymmetric wedge channel structure of shorebird beaks, this work proposes a spine with hierarchical microchannels and wedge channels (SHMW). Due to the synergistic effect of capillary force and asymmetric Laplace force, the SHMW can rapidly separate mixed organic droplets into two pure phases without requiring additional energy. In particular, the self-spreading of the oil solution on the open channel surface is utilized to amplify the surface energy difference between two droplets, and SHMW achieves the pickup of oil droplets floating on the surface of the organic solution. The maximum separation efficiency on 3-SHMW can reach 99.63%, and it can also realize the antigravity separation of mixed organic droplets with a surface tension difference as low as 0.87 mN·m-1. Furthermore, SHMW performs controllable separation, oil droplet pickup, and continuous separation and collection of mixed organic droplets. It is expected that this cooperative structure composed of hierarchical microchannels and wedge channels will be realized in resource recovery or chemical reactions in industrial production processes.

Droplet Rolling Transport on Hydrophobic Surfaces Under Rotating Electric Fields: A Molecular Dynamics Study

Driving droplets by electric fields is usually achieved by controlling their wettability, and realizing a flexible operation requires complex electrode designs. Here, we show by molecular dynamics methods the droplet transport on hydrophobic surfaces in a rolling manner under a rotating electric field, which provides a simpler and promising way to manipulate droplets. The droplet internal velocity field shows the rolling mode. When the contact angle on the solid surface is 144.4°, the droplet can be transported steadily at a high velocity under the rotating electric field (E = 0.5 V nm-1, ω = π/20 ps-1). The droplet center-of-mass velocities and trajectories, deformation degrees, dynamic contact angles, and surface energies were analyzed regarding the electric field strength and rotational angular frequency. Droplet transport with a complex trajectory on a two-dimensional surface is achieved by setting the electric field, which reflects the programmability of the driving method. Nonuniform wettability stripes can assist in controlling droplet trajectories. The droplet transport on the three-dimensional surface is studied, and the critical conditions for the droplet passing through the surface corners and the motion law on the curved surface are obtained. Droplet coalescence has been achieved by surface designs.

Emerging open-channel droplet arrays for biosensing

Open-channel droplet arrays have attracted much attention in the fields of biochemical analysis, biofluid monitoring, biomarker recognition and cell interactions, as they have advantages with regard to miniaturization, parallelization, high-throughput, simplicity and accessibility. Such droplet arrays not only improve the sensitivity and accuracy of a biosensor, but also do not require sophisticated equipment or tedious processes, showing great potential in next-generation miniaturized sensing platforms. This review summarizes typical examples of open-channel microdroplet arrays and focuses on diversified biosensing integrated with multiple signal-output approaches (fluorescence, colorimetric, surface-enhanced Raman scattering (SERS), electrochemical, etc.). The limitations and development prospects of open-channel droplet arrays in biosensing are also discussed with regard to the increasing demand for biosensors.

A UV-Resistant Heterogeneous Wettability-Patterned Surface

Preparing UV-resistant heterogeneous wettability patterns is critical for the practical application of surfaces with heterogeneous wettability. However, combining UV-resistant superhydrophobic and superhydrophilic materials on heterogeneous surfaces is challenging. Inspired by the structure of cell membranes, a UV-resistant heterogeneous wettability-patterned surface (UPS) is designed via laser ablation of the coating of multilayer structures. UV-resistant superhydrophobic silica patterns can be created in situ on surfaces covered with superhydrophilic TiO2 nanoparticles. The UV resistance time of the UPS with a TiO2 -based surface is more than two orders of magnitude higher than that obtained with other surface molecular modification methods that require a mask. The cell-membrane-like structure of the UPS regulates the migration of internal siloxane chain segments in the hydrophilic and hydrophobic regions of the surface. The UPS enables efficient patterning of functional materials under UV irradiation, controlling the wetting behavior of liquids in open-air systems. Furthermore, its heterogeneous wettability remains stable even after 50 h of intense UV irradiation (365 nm, 500 mW cm-2 ). These UV-resistant heterogeneous wettability patterned surfaces will likely be applied in microfluidics, cell culture, energy conversion, and water collection in the future.

Self-Oxidation Resistance of the Curved Surface of Achromatic Copper

Copper surfaces that exhibit a wide range of achromatic colors while still metallic have not been studied, despite advancements in antireflection coatings. A series of achromatic copper films grown with [111] preferred orientation by depositing 3D porous nanostructures is introduced via coherent/incoherent atomic sputtering epitaxy. The porous copper nanostructures self-regulate the giant oxidation resistance by constructing a curved surface that generates a series of monoatomic steps, followed by shrinkage of the lattice spacing of one or two surface layers. First-principles calculations confirm that these structural components cooperatively increase the energy barrier against oxygen penetration. The achromaticity of the single-crystalline porous copper films is systematically tuned by geometrical parameters such as pore size distribution and 3D linkage. The optimized achromatic copper films with high oxidation resistance show an unusual switching effect between superhydrophilicity and superhydrophobicity. The tailored 3D porous nanostructures can be a candidate material for numerous applications, such as antireflection coatings, microfluidic devices, droplet tweezers, and reversible wettability switches.

Efficient Surfactant-Mediated Photovoltaic Manipulation of fL-Scale Aqueous Microdroplets for Diverse Optofluidic Applications on LiNbO3 Platform

The electrodeless biocompatible manipulation of femtoliter-scale aqueous microdroplets remains challenging. The appropriate isolation of electrostatic charges from femtoliter-scale aqueous microdroplets is crucial for electrodeless optoelectronic manipulation based on space-charge-density modulation. Here, surfactant-mediated photovoltaic manipulation is proposed, where the surfactant layers self-assembled at the water-oil and oil-Lithium niobate interfaces are employed to isolate photovoltaic charges. The reduced electrostatic attenuation, remarkable hydrophobicity, and strong electrical breakdown suppression of the surfactant layers enable the stable and swift manipulation of femtoliter-scale aqueous microdroplets using µW-level laser in oil media. By virtue of the surfactant-mediated photovoltaic manipulation, a controllable merging/touching/detaching switch of aqueous microdroplets by adjusting the laser illumination intensity and position is realized and the cascading biochemical operations and microreactions of aqueous microdroplets and microdroplet strings are demonstrated. To demonstrate its potential in photonic Micro-Electro-Mechanical-System assemblies, the end coupling of a focused-laser-beam into a ZnO microrod leveraging the refraction effect occurring at the water/oil interface is demonstrated. Moreover, because of the selective permeability of the droplet-interface-bilayer developed between the touching microdroplets, in situ adjustment of the size of the microdroplets and the fluorescent solute contained in the microdroplets are achieved, aiming at constructing multicomponent fluorescent microdroplets with tunable whispering-gallery-mode characteristics.

Miniaturizing chemistry and biology using droplets in open systems

Open droplet microfluidic systems manipulate droplets on the picolitre-to-microlitre scale in an open environment. They combine the compartmentalization and control offered by traditional droplet-based microfluidics with the accessibility and ease-of-use of open microfluidics, bringing unique advantages to applications such as combinatorial reactions, droplet analysis and cell culture. Open systems provide direct access to droplets and allow on-demand droplet manipulation within the system without needing pumps or tubes, which makes the systems accessible to biologists without sophisticated setups. Furthermore, these systems can be produced with simple manufacturing and assembly steps that allow for manufacturing at scale and the translation of the method into clinical research. This Review introduces the different types of open droplet microfluidic system, presents the physical concepts leveraged by these systems and highlights key applications.

Amoeba-Inspired Magnetic Venom Microrobots

Nature provides a successful evolutionary direction for single-celled organisms to solve complex problems and complete survival tasks - pseudopodium. Amoeba, a unicellular protozoan, can produce temporary pseudopods in any direction by controlling the directional flow of protoplasm to perform important life activities such as environmental sensing, motility, predation, and excretion. However, creating robotic systems with pseudopodia to emulate environmental adaptability and tasking capabilities of natural amoeba or amoeboid cells remains challenging. Here, this work presents a strategy that uses alternating magnetic fields to reconfigure magnetic droplet into Amoeba-like microrobot, and the mechanisms of pseudopodia generation and locomotion are analyzed. By simply adjusting the field direction, microrobots switch in monopodia, bipodia, and locomotion modes, performing all pseudopod operations such as active contraction, extension, bending, and amoeboid movement. The pseudopodia endow droplet robots with excellent maneuverability to adapt to environmental variations, including spanning 3D terrains and swimming in bulk liquids. Inspired by the "Venom," the phagocytosis and parasitic behaviors have also been investigated. Parasitic droplets inherit all the capabilities of amoeboid robot, expanding their applicable scenarios such as reagent analysis, microchemical reactions, calculi removal, and drug-mediated thrombolysis. This microrobot may provide fundamental understanding of single-celled livings, and potential applications in biotechnology and biomedicine.

One-Step Fabrication of Droplet Arrays Using a Biomimetic Structural Chip

In the field of one-step efficient preparation of dewetting droplet arrays, the process is hampered by the requirement for low chemical wettability of solid surfaces, which restricts the complete transition of wetting state and its broad prospects in biological applications. Inspired by the physical structure of the lotus leaf, enabling it to promote the change of the infiltration state of an aqueous solution on the surface, we developed a method of one-step fabrication of droplet arrays on the biomimetic structural chip designed in the present work. This greatly reduces the need for chemical modification techniques to achieve low wettability and reduces the reliance on complex and sophisticated surface preparation techniques, thus improving the fabrication efficiency of droplet arrays fully generated on a chip by one-step operation without the need for extra liquid phase or the control of harsh barometric pressure. We also studied the influence of dimensions of the biomimetic structure and the preparation process parameters such as number of smears and speed of smearing on the preparation rate and uniformity of the droplet arrays. The amplification of templating DNA molecules in the droplet arrays prepared in a one-step fabrication way is also performed to verify its application potential for DNA molecular diagnosis.

Mosaic Patterned Surfaces toward Generating Hardly-Volatile Capsular Droplet Arrays for High-Precision Droplet-Based Storage and Detection

Precise detection involving droplets based on functional surfaces is promising for the parallelization and miniaturization of platforms and is significant in epidemic investigation, analyte recognition, environmental simulation, combinatorial chemistry, etc. However, a challenging and considerable task is obtaining mutually independent droplet arrays without cross-contamination and simultaneously avoiding droplet evaporation-caused quick reagent loss, inaccuracy, and failure. Herein, a strategy to generate mutually independent and hardly-volatile capsular droplet arrays using innovative mosaic patterned surfaces is developed. The evaporation suppression of the capsular droplet arrays is 1712 times higher than the naked droplet. The high evaporation suppression of the capsular droplet arrays on the surfaces is attributed to synergistic blocking of the upper oil and bottom mosaic gasproof layer. The scale-up of the capsular droplet arrays, the flexibility in shape, size, component (including aqueous, colloidal, acid, and alkali solutions), liquid volume, and the high-precision hazardous substance testing proves the concept's high compatibility and practicability. The mutually independent capsular droplet arrays with amazingly high evaporation suppression are essential for the new generation of high-performance open-surface microfluidic chips used in COVID-19 diagnosis and investigation, primary screening, in vitro enzyme reactions, environmental monitoring, nanomaterial synthesis, etc.

Hierarchical hydrogel microarrays fabricated based on a microfluidic printing platform for high-throughput screening of stem cell lineage specification

2D cell cultures are suitable for rapid exploration of the factors in the extracellular matrix affecting the development of cells. The technology of the micrometre-sized hydrogel array provides a feasible, miniaturized, and high-throughput strategy for the process. However, current microarray devices lack a handy and parallelized methodology in sample treatment, which makes the process of high-throughput cell screening (HTCS) expensive and inefficient. Here, based on the functionalization of micro-nano structures and the fluid control capability of microfluidic chips, we build a microfluidic spotting-screening platform (MSSP). The MSSP can print 20000 microdroplet spots within 5 min, coupled with a simple strategy for parallel addition of compound libraries. Compared with open microdroplet arrays, the MSSP can control the evaporation rate of nanoliter droplets, providing a stable fabrication platform for hydrogel-microarray-based materials. As a proof-of-concept demonstration, the MSSP successfully controlled the adhesion, adipogenic, and osteogenic differentiation behavior of mesenchymal stem cells by rationally designing the substrate stiffness, adhesion area, and cell density. We anticipate that the MSSP may provide an accessible and promising tool for hydrogel-based HTCS. STATEMENT OF SIGNIFICANCE: High-throughput screening of cells is a common approach to improve the efficiency of biological experiments, and one challenge of the existing technologies is to achieve rapid and precise cell screening with a low-cost and simple strategy. Through the integration of the microfluidic and micro-nanostructure technologies, we fabricated a microfluidic spotting-screening platforms. Benefiting from the flexible control of the fluids, the device can print 20000 microdroplet spots within 5 min, coupled with a simple procedure for parallel addition of compound libraries. High-throughput screening of stem cell lineage specification has also been achieved by the platform, which provides a high-throughput, high-content information extraction strategy for cell-biomaterial interaction research.

Back to Basics: A Simplified Improvement to Multiple Displacement Amplification for Microbial Single-Cell Genomics

Microbial single-cell genomics (SCG) provides access to the genomes of rare and uncultured microorganisms and is a complementary method to metagenomics. Due to the femtogram-levels of DNA in a single microbial cell, sequencing the genome requires whole genome amplification (WGA) as a preliminary step. However, the most common WGA method, multiple displacement amplification (MDA), is known to be costly and biased against specific genomic regions, preventing high-throughput applications and resulting in uneven genome coverage. Thus, obtaining high-quality genomes from many taxa, especially minority members of microbial communities, becomes difficult. Here, we present a volume reduction approach that significantly reduces costs while improving genome coverage and uniformity of DNA amplification products in standard 384-well plates. Our results demonstrate that further volume reduction in specialized and complex setups (e.g., microfluidic chips) is likely unnecessary to obtain higher-quality microbial genomes. This volume reduction method makes SCG more feasible for future studies, thus helping to broaden our knowledge on the diversity and function of understudied and uncharacterized microorganisms in the environment.

Surface Modification, Topographic Design and Applications of Superhydrophobic Systems

Superhydrophobic surfaces with expanded wetting behaviors, like tunable adhesion, hybrid surface hydrophobicity and smart hydrophobic switching have attracted increasing attention due to their broad applications. Herein, the construction methods, mechanisms and advanced applications of special superhydrophobicity are reviewed, and hydro/superhydrophobic modifications are categorized and discussed based on their surface chemistry, and topographic design. The formation and maintenance of special superhydrophobicity in the metastable state are also examined and explored. In addition, particular attention is paid to the use of special wettability in various applications, such as membrane distillation, droplet-based electricity generators and anti-fogging surfaces. Finally, the challenges for practical applications and future research directions are discussed.

Split-Ring Structured All-Inorganic Perovskite Photodetector Arrays for Masterly Internet of Things

Photodetectors with long detection distances and fast response are important media in constructing a non-contact human-machine interface for the Masterly Internet of Things (MIT). All-inorganic perovskites have excellent optoelectronic performance with high moisture and oxygen resistance, making them one of the promising candidates for high-performance photodetectors, but a simple, low-cost and reliable fabrication technology is urgently needed. Here, a dual-function laser etching method is developed to complete both the lyophilic split-ring structure and electrode patterning. This novel split-ring structure can capture the perovskite precursor droplet efficiently and achieve the uniform and compact deposition of CsPbBr3 films. Furthermore, our devices based on laterally conducting split-ring structured photodetectors possess outstanding performance, including the maximum responsivity of 1.44 × 105 mA W-1, a response time of 150 μs in 1.5 kHz and one-unit area < 4 × 10-2 mm2. Based on these split-ring photodetector arrays, we realized three-dimensional gesture detection with up to 100 mm distance detection and up to 600 mm s-1 speed detection, for low-cost, integrative, and non-contact human-machine interfaces. Finally, we applied this MIT to wearable and flexible digital gesture recognition watch panel, safe and comfortable central controller integrated on the car screen, and remote control of the robot, demonstrating the broad potential applications.

On-demand, remote and lossless manipulation of biofluid droplets

The recent global outbreaks of epidemics and pandemics have shown us that we are severely under-prepared to cope with infectious agents. Exposure to infectious agents present in biofluids (e.g., blood, saliva, urine etc.) poses a severe risk to clinical laboratory personnel and healthcare workers, resulting in hundreds of millions of hospital-acquired and laboratory-acquired infections annually. Novel technologies that can minimize human exposure through remote and automated handling of infectious biofluids will mitigate such risk. In this work, we present biofluid manipulators, which allow on-demand, remote and lossless manipulation of virtually any liquid droplet. Our manipulators are designed by integrating thermo-responsive soft actuators with superomniphobic surfaces. Utilizing our manipulators, we demonstrate on-demand, remote and lossless manipulation of biofluid droplets. We envision that our biofluid manipulators will not only reduce manual operations and minimize exposure to infectious agents, but also pave the way for developing inexpensive, simple and portable robotic systems, which can allow point-of-care operations, particularly in developing nations.

A magnetic responsive composite surface for high-performance droplet and bubble manipulation

Here, a magnetic responsive composite surface (MRCS) was prepared by injecting a magnetic elastomer into ZnO nanoarrays for intelligent control of droplet/bubble transport. This non-pollution, non-contact operation method has shown great potential in micro-fluids, micro-chemical reactors, chip laboratory environments and other related applications.

Superhydrophilic–superhydrophobic patterned surfaces: From simplified fabrication to emerging applications

Superhydrophilic–superhydrophobic patterned surfaces constitute a branch of surface chemistry involving the two extreme states of superhydrophilicity and superhydrophobicity combined on the same surface in precise patterns. Such surfaces have many advantages, including controllable wettability, enrichment ability, accessibility, and the ability to manipulate and pattern water droplets, and they offer new functionalities and possibilities for a wide variety of emerging applications, such as microarrays, biomedical assays, microfluidics, and environmental protection. This review presents the basic theory, simplified fabrication, and emerging applications of superhydrophilic–superhydrophobic patterned surfaces. First, the fundamental theories of wettability that explain the spreading of a droplet on a solid surface are described. Then, the fabrication methods for preparing superhydrophilic–superhydrophobic patterned surfaces are introduced, and the emerging applications of such surfaces that are currently being explored are highlighted. Finally, the remaining challenges of constructing such surfaces and future applications that would benefit from their use are discussed.

Nanoextraction based on surface nanodroplets for chemical preconcentration and determination

Liquid-liquid extraction based on surface nanodroplets, namely nanoextraction, can continuously extract and enrich target analytes from the flow of a sample solution. This sample preconcentration technique is easy to operate in a continuous flow system with a low consumption of organic solvent and a high enrichment factor. In this review, the evolution from single drop microextraction to advanced nanoextraction will be briefly introduced. Moreover, the formation principle and key features of surface nanodroplets will be summarized. Further, the major findings of nanoextraction combined with in-droplet chemistry toward sensitive and quantitative detection will be discussed. Finally, we will give our perspectives for the future trend of nanoextraction.

A Reactive Superhydrophobic Platform for Living Photolithography

Superhydrophobic surfaces with regional functions have widespread applications in biotechnology, diagnostic applications, and micro-chemical synthesis and analysis. However, owing to their chemical inertness, superhydrophobic surfaces with chemical reactivity are difficult to achieve. Superhydrophobic surfaces that can be further modified with varied densities and expanded species of the functional moieties are not readily available. In this study, a single-step approach to achieve a reactive superhydrophobic surface is reported, on which chemical grafting of a library of molecules can be carried out through surface-initiated atom-transfer radical addition or surface-initiated atom-transfer radical polymerization. The excellent spatial and temporal controllability of these chemical processes under visible light enables us to take advantage of programmed liquid-crystal-display (LCD) or Digital Light Processing (DLP) photolithography systems to effortlessly regulate the location, density, and species of the functional molecules on the reactive superhydrophobic surface. The distinctive properties of this surface will provide new insight into intelligent superhydrophobic material development and practical applications, such as aqueous/oil microdroplets array, multi-anti-counterfeiting labels and integrated microfluidic reactors with enzymes for chemical logic learning.

Tri-templating Synthesis of Multilevel Mesoporous Silica Microspheres with a Complex Interior Structure for Efficient CO2 Capture and Catalysis

Multilevel porous architectures with microscopic shape control and tailor-made complex structures offer great potential for various innovative applications, but their elaborate design and synthesis have remained a scientific and technological challenge. Herein, we report a simple and effective tri-templating method, in which microscale Pickering droplets, nanoscale polystyrene colloids (PS), and molecular cetyltrimethylammonium chloride micelles are synchronously employed, for the fabrication of such micro-nanohierarchical mesoporous silica microspheres. In this protocol, Pickering droplet-directed interfacial sol-gel growth and its spatially confined surfactant assembly-directed sol-gel coating on PS suspensions are coupled together, enabling the successful formation of structured mesoporous silica that consists of numerous nanocompartments enclosed by a permeable shell. By varying the quantity of PS colloidal templates, rational regulation of the complex interior structure is achieved. Also, ascribed to the multilevel arrangement, this peculiar architecture not only shows desirable fast mass transport of external molecules but also possesses easy handling ability. After loading with tetraethylenepentamine or enzyme species, the yielded microspherical CO₂ sorbents or immobilized biocatalysts, respectively, exhibit enhanced CO₂ capture capacity and enzymatic catalysis efficiency. Notably, taking advantage of their microscopic characteristics, the immobilized biocatalysts could be ideally packed in a fixed-bed reactor for long-term continuous-flow enzymatic reactions. This tri-templating strategy provides a new synthetic route to access other multilevel microscopic materials with fascinating complex structures and paves a way to promote their practical applications.

Micro-object manipulation by decanol liquid lenses

The flexible and precise manipulation of droplets on an air-liquid interface with complex functions remains challenging. Herein, we propose a smart strategy for excellently manipulating target droplets by decanol liquid lenses. A moveable surface tension gradient field generated by decanol liquid lenses is responsible for realizing various functions of transportation, launching and splitting of target droplets. With such fascinating features, directional long-distance transportation and on-demand droplet coalescence are enabled. Moreover, paw-like liquid lenses are constructed, which realizes a complex process, including collection, capture, transportation and release of target droplets. Remarkably, this strategy can also be applied to manipulate particles and liquid marbles other than droplets, eliminating the limitation of object properties. This work offers a smart strategy for manipulating micro-objects, which shows great potential in applications such as lab-on-a-chip, diagnostics, analytical chemistry and bioengineering, etc.

Shape-Reconfigurable Ferrofluids

Ferrofluids (FFs) can adapt their shape to a magnetic field. However, they cannot maintain their shape when the magnetic field is removed. Here, with a magneto-responsive and reconfigurable interfacial self-assembly (MRRIS) process, we show that FFs can be structured by a magnetic field and maintain their shape, like solids, after removing the magnetic field. The competing self-assembly of magnetic and nonmagnetic nanoparticles at the liquid interface endow FFs with both reconfigurability and structural stability. By manipulating the external magnetic field, we show that it is possible to "write" and "erase" the shape of the FFs remotely and repeatedly. To gain an in-depth understanding of the effect of MRRIS on the structure of FFs, we systematically study the shape variation of these liquids under both the static and dynamic magnetic fields. Our study provides a simple yet novel way of manipulating FFs and opens opportunities for the fabrication of all-liquid devices.

Growth Rates of Hydrogen Microbubbles in Reacting Femtoliter Droplets

Chemical reactions in small droplets are extensively explored to accelerate the discovery of new materials and increase the efficiency and specificity in catalytic biphasic conversion and high-throughput analytics. In this work, we investigate the local rate of the gas-evolution reaction within femtoliter droplets immobilized on a solid surface. The growth rate of hydrogen microbubbles (≥500 nm in radius) produced from the reaction was measured online with high-resolution confocal microscopic images. The growth rate of bubbles was faster in smaller droplets and near the droplet rim in the same droplet. The results were consistent for both pure and binary reacting droplets and on substrates of different wettability. Our theoretical analysis based on diffusion, chemical reaction, and bubble growth predicted that the concentration of the reactant depended on the droplet size and the bubble location inside the droplet, in good agreement with experimental results. Our results reveal that the reaction rate may be spatially nonuniform in the reacting microdroplets. The findings may have implications for formulating the chemical properties and uses of these droplets.

Oil-Triggered and Template-Confined Dewetting for Facile and Low-Loss Sample Digitization

This paper proposes a simple and robust method for spontaneously digitizing aqueous samples into a high-density microwell array. The method is based on an oil-triggered template-confined dewetting phenomenon. To realize the dewetting-induced sample digitization, an aqueous sample is first infused into a networked microwell array (NMA) through a pre-degassing-based self-pumping mechanism, and an immiscible oil phase is then applied over the surface of NMA chip to induce the templated dewetting. Due to periodic interfacial tension heterogeneity, such dewetting ruptures the sample at the thinnest parts (i.e., connection channels) and spontaneously splits the sample into droplets in individual microwells. Without requiring any complex pumping or valving systems, this method can discretize a sample into tens of thousands of addressable droplets in a matter of minutes with nearly 98% usage. To demonstrate the utility and universality of this self-digitization method, we exploited it to discretize samples into 40 233 wells for a digital PCR assay, the digital quantification of bacteria, the self-assembly of spherical colloidal photonic crystals, and the spherical crystallization of drugs. We believe this facile technique will provide a substantial benefit to many compartmentalized assays or syntheses where it is necessary to partition samples into a large number of small individual volumes.

Inkjet-Patterned Microdroplets as Individual Microenvironments for Adherent Single Cell Culture

Adhesion of single cells is the foundation of manifold cellular behaviors and life processes. However, investigating the function of a specific cell is still challenging due to deficiency of adhesion or interference from surrounding cells. Herein, an open microfluidic system is reported for culturing adherent single cells, implemented by a micrometer-scale droplet matrix on an inkjet-printed polylysine template. The target cells are isolated from any cell from other droplets, and their adhesion strength is determined to be comparable to conventional petri dishes via an in-situ investigation with a microfluidic extractor. On this proposed platform, isolated single cells are observed to display an entirely distinct spreading behavior featuring total absence of elongation, indicating drastic cell behavior change from their "singleness." This system has high versatility and compatibility for various assaying methods, assuring a promising potential in detailed single cell behavior and cell heterogeneity studies.

Responsive Liquid Metal Droplets: From Bulk to Nano

Droplets exist widely in nature and play an extremely important role in a broad variety of industrial processes. Typical droplets, including water and oil droplets, have received extensive attention and research, however their single properties still cannot meet diverse needs. Fortunately, liquid metal droplets emerging in recent years possess outstanding properties, including large surface tension, excellent electrical and thermal conductivity, convenient chemical processing, easy transition between liquid and solid phase state, and large-scale deformability, etc. More interestingly, liquid metal droplets with unique features can respond to external factors, including the electronic field, magnetic field, acoustic field, chemical field, temperature, and light, exhibiting extraordinary intelligent response characteristics. Their development over the past decade has brought substantial breakthroughs and progress. To better promote the advancement of this field, the present article is devoted to systematically summarizing and analyzing the recent fundamental progress of responsive liquid metal droplets, not only involving droplet characteristics and preparation methods, but also focusing on their diverse response behaviors and mechanisms. On this basis, the challenges and prospects related to the following development of liquid metal droplets are also proposed. In the future, responsive liquid metal droplets with a rapid development trend are expected to play a key role in soft robots, biomedicine, smart matter, and a variety of other fields.

Rapid Mass Spectrometric Calibration and Standard Addition Using Hydrophobic/Hydrophilic Patterned Surfaces and Discontinuous Dewetting

The rapid calibration chip (RCC) is a device that uses the fast and reproducible wetting behavior of hydrophilic/hydrophobic patterned surfaces to confine a series of differently sized droplets on a substrate to obtain a calibration curve. Multiple series of droplets can be formed within seconds by dipping an RCC into a calibration solution. No pipetting, sequential droplet deposition, or advanced equipment is required. The performance and reproducibility of RCCs were evaluated with an electrospray ionization triple-quadrupole mass spectrometer equipped with a liquid microjunction-surface sampling probe (LMJ-SSP) that allows for fast sampling of surfaces. Using circular hydrophilic areas with diameters ranging from 0.25 to 2.00 mm, liquid volumes of 4.6-70.6 nL could be deposited. Furthermore, the use of a second hydrophobic/hydrophilic patterned transfer chip can be used to add internal standard solutions to each calibration spot of the RCC, allowing to transfer a liquid volume of 22.5 nL.

Fish Capsules: A System for High-Throughput Screening of Combinatorial Drugs

Large-scale screening of molecules heavily relies on phenotyping of small living organisms during preclinical development. However, deep profiling candidate therapeutics on whole animals typically requires laborious manipulations and anesthetic treatment using traditional techniques or automated tools. Here, a novel fish capsule system that combines automated zebrafish encapsulating technology and droplet microarray strategy for in vivo functional screening of mono/polytherapies is described. This platform enables automated, rapid zebrafish orientation and immobilization in agarose to generate large-scale fish capsules by using a microfluidic device. Based on the effect of discontinuous dewetting, the prompt trapping of fish capsules in the aqueous arrays is successfully demonstrate. This system provides the capability to integrate pharmaceutical treatments with real-time multispectral microscopic imaging in a simple, pipetting-free and highly parallel manner. Coupling with machine learning algorithms, a small library of compounds is screened and analyzed, and clues about how to exploit compound combinations as therapeutic candidates are obtained. It is believed that this proposed strategy can be readily applied to multiple fields and is especially useful in the exploration of combinatorial drugs with limited amounts of samples and resources to accelerate the identification of novel therapeutics for precision medicines.

Endogenous Electric-Field-Coupled Electrospun Short Fiber via Collecting Wound Exudation

Endogenous electric fields (EF) are the basis of bioelectric signal conduction and the priority signal for damaged tissue regeneration. Tissue exudation directly affects the characteristics of endogenous EF. However, current biomaterials lead to passive repair of defect tissue due to limited management of early wound exudates and inability to actively respond to coupled endogenous EF. Herein, the 3D bionic short-fiber scaffold with the functions of early biofluid collection, response to coupled endogenous EF, is constructed by guiding the short fibers into a 3D network structure and subsequent multifunctional modification. The scaffold exhibits rapid reversible water absorption, reaching maximum after only 30 s. The stable and uniform distribution of polydopamine-reduced graphene oxide endows the scaffold with stable electrical and mechanical performances even after long-term immersion. Due to its unique - bionic structure and tissue affinity, the scaffold further acts as an "electronic skin," which transmits endogenous bioelectricity via absorbing wound exudates, promoting the treatment of diabetic wounds. Furthermore, under the endogenous EF, the cascade release of vascular endothelial growth factor accelerates the healing process. Thus, the versatile scaffold is expected to be an ideal candidate for repairing different defect tissues, especially electrosensitive tissues.

Portable electrochemical micro-workstation platform for simultaneous detection of multiple Alzheimer's disease biomarkers

Alzheimer's disease, as a most prevalent type of dementia, is quickly becoming one of the most expensive, lethal, and burdening diseases of this century. Though there are still no efficient therapies, early diagnosis and intervention are important directive significance to clinical works. Here, we develop a portable electrochemical micro-workstation platform consisting of an electrochemical micro-workstation and integrated electrochemical microarray for simultaneously detecting multiple AD biomarkers including Aβ40, Aβ42, T-tau, and P-tau181 in serum. The integrated electrochemical microarray is mainly used for droplet sample manipulation and signal generation. The micro-workstation can regulate signals and transfer the signals to a smartphone by Bluetooth embedded inside. This portable electrochemical micro-workstation platform exhibits excellent analysis performance. The LODs for Aβ40, Aβ42, T-tau, and P-tau181 are 0.125 pg/mL, 0.089 pg/mL, 0.142 pg/mL, and 0.176 pg/mL, respectively, which satisfies the needs of detecting AD biomarkers in serum. The combination of portable micro-workstation and integrated electrochemical microarray provides a promising strategy for the early diagnosis of Alzheimer's disease and personal healthcare.