Bio-Inspired Dopamine Functionalization of Polypyrrole for Improved Adhesion and Conductivity

Label-free electrochemical biosensor based on dual amplification of gold nanoparticles and polycaprolactones for CEA detection

Carcinoembryonic Antigen (CEA), an acidic glycoprotein with human embryonic antigen properties, is found on the surface of cancer cells that have differentiated from endodermal cells. This paper presents a label-free electrochemical immunoassay for the dual amplification detection of CEA using gold nanoparticles loaded with polypyrrole polydopamine (Au/PPy-PDA) and polymerized polycaprolactone (Ng-PCL) prepared by ring-opening polymerization (ROP). First, the composite Au/PPy-PDA was adhered to the electrode surface. Then, gold nanoparticles form a Au-S bond with the sulfhydryl group in Apt1 to secure it on the electrode surface. Subsequently, the non-specific binding sites on the electrodes surface are closed by bovine serum albumin (BSA). Next, CEA is dropped onto the electrode surface, which is immobilized by antigen-antibody specific recognition, and the carboxyl-functionalized Apt2 forms a "sandwich structure" of antibody-antigen-antibody by specific recognition. Polymeric Ng-PCL is adhered to the electrode surface, leading to an increase in the electrochemical impedance signal, resulting in a complete chain of signal analysis. Finally, the response signal is detected by electrochemical impedance spectroscopy (EIS). Under optimal experimental conditions, the method has the advantages of high sensitivity and wide linear range (1 pg mL-1∼100 ng mL-1), and the lower limit of detection (LOD) is 0.234 pg mL-1. And it has the same high sensitivity, selectivity and interference resistance for the real samples detection. Thus, it provides a new way of thinking about biomedical and clinical diagnosis.

Mechanism of Self-Oxidative Copolymerization and its Application with Polydopamine-pyrrole Nano-copolymers

Currently, the copolymer of dopamine (DA) and pyrrole (PY) via chemical and electrochemical oxidation usually requires additional oxidants, and lacks flexibility in regulating the size and morphology, thereby limiting the broad applications of DA-PY copolymer in biomedicine. Herein, the semiquinone radicals produced by the self-oxidation of DA is ingeniously utilized as the oxidant to initiate the following copolymerization with PY, and a series of quinone-rich polydopamine-pyrrole copolymers (PDAm-nPY) with significantly enhanced absorption in near-infrared (NIR) region without any additional oxidant assistance is obtained. Moreover, the morphology and size of PDAm-nPY can be regulated by changing the concentration of DA and PY, thereby optimizing nanoscale PDA0.05-0.15PY particles (≈ 150 nm) with excellent NIR absorption and surface modification activity are successfully synthesized. Such PDA0.05-0.15PY particles show effective photoacoustic (PA) imaging and photothermal therapy (PTT) against 4T1 tumors in vivo. Furthermore, other catechol derivatives can also copolymerize with PY under the same conditions. This work by fully utilizing the semiquinone radical active intermediates produced through the self-oxidation of DA reduces the dependence on external oxidants in the synthesis of composite materials and predigests the preparation procedure, which provides a novel, simple, and green strategy for the synthesis of other newly catechol-based functional copolymers.

Surface Modification Progress for PLGA-Based Cell Scaffolds

Poly(lactic-glycolic acid) (PLGA) is a biocompatible bio-scaffold material, but its own hydrophobic and electrically neutral surface limits its application as a cell scaffold. Polymer materials, mimics ECM materials, and organic material have often been used as coating materials for PLGA cell scaffolds to improve the poor cell adhesion of PLGA and enhance tissue adaptation. These coating materials can be modified on the PLGA surface via simple physical or chemical methods, and coating multiple materials can simultaneously confer different functions to the PLGA scaffold; not only does this ensure stronger cell adhesion but it also modulates cell behavior and function. This approach to coating could facilitate the production of more PLGA-based cell scaffolds. This review focuses on the PLGA surface-modified materials, methods, and applications, and will provide guidance for PLGA surface modification.

Implantable Nerve Conduit Made of a Self-Powered Microneedle Patch for Sciatic Nerve Repair

Peripheral nerve defects, particularly those of a larger size, pose a significant challenge in clinical practice due to their limited regenerative capacity. To tackle this challenge, an advanced self-powered enzyme-linked microneedle (MN) nerve conduit is designed and fabricated. This innovative conduit is composed of anodic and cathodic MN arrays, which contain glucose oxidase (GOx) and horseradish peroxidase (HRP) encapsulated in ZIF-8 nanoparticles, respectively. Through an enzymatic cascade reaction, this MN nerve conduit generates microcurrents that stimulate the regeneration of muscles, blood vessels, and nerve fibers innervated by the sciatic nerve, eventually accelerating the repair of sciatic nerve injury. It is clear that this self-powered MN nerve conduit will revolutionize traditional treatment methods for sciatic nerve injury and find widespread application in the field of nerve tissue repair.

Chemically revised conducting polymers with inflammation resistance for intimate bioelectronic electrocoupling

Conducting polymers offer attractive mixed ionic-electronic conductivity, tunable interfacial barrier with metal, tissue matchable softness, and versatile chemical functionalization, making them robust to bridge the gap between brain tissue and electronic circuits. This review focuses on chemically revised conducting polymers, combined with their superior and controllable electrochemical performance, to fabricate long-term bioelectronic implants, addressing chronic immune responses, weak neuron attraction, and long-term electrocommunication instability challenges. Moreover, the promising progress of zwitterionic conducting polymers in bioelectronic implants (≥4 weeks stable implantation) is highlighted, followed by a comment on their current evolution toward selective neural coupling and reimplantable function. Finally, a critical forward look at the future of zwitterionic conducting polymers for in vivo bioelectronic devices is provided.

Microwave Gas Sensors Based on Electrodeposited Polypyrrole-Nickel Phthalocyanine Hybrid Films

Previous studies have shown that the incorporation of sulfonated metallophthalocyanines into sensitive sensor materials can improve electron transfer and thus species detection. Herein, we propose a simple and easy alternative to the use of generally expensive sulfonated phthalocyanines by electropolymerizing polypyrrole together with nickel phthalocyanine in the presence of an anionic surfactant. The addition of the surfactant not only helps the incorporation of the water-insoluble pigment into the polypyrrole film, but the obtained structure has increased hydrophobicity, which is a key property for developing efficient gas sensors with low sensitivity to water. The obtained results show the effectiveness of the materials tested for the detection of ammonia in the range of 100 to 400 ppm. It is shown by comparing the microwave sensor responses that the film without nickel phthalocyanine (hydrophilic) produces greater variations than the film with nickel phthalocyanine (hydrophobic). These results are consistent with the expected results since the hydrophobic film is not very sensitive to residual ambient water and therefore does not interfere with the microwave response. However, although this excess response is usually a handicap, as it is a source of drift, in these experiments the microwave response shows great stability in both cases.

Polydopamine/polypyrrole-modified graphite felt enhances biocompatibility for electroactive bacteria and power density of microbial fuel cell

The interactions between the microbes and the surface of an anode play an important role in capturing the respiratory electrons from bacteria in a microbial fuel cell (MFC). The chemical and electrochemical characteristics of the carbon material affect biofilm growth and direct electron transfer in MFCs. This study examined the electrodeposition of polydopamine (PDA) and polypyrrole (PPY) on graphite felt electrode (GF). The MFC with the modified PDA/PPY-GF reached 920 mW/m², which was 1.5, 1.17, and 1.18 times higher than those of the GF, PDA-GF, and PPY-GF, respectively. PDA has superior hydrophilicity and adhesive force biofilm formation, while PPY provides electrochemically active sites for microbial electron transfer. Raman spectroscopy, Fourier transform infrared spectroscopy, Brunauer-Emmett-Teller surface area measurements, and contact angle analysis revealed the enhanced physicochemical properties of the carbon electrode. These results show that co-doped PDA/PPY provides a strategy for electroactive biofilm development and improves the bioelectrochemical performance in realistic MFC reactors.

Polypyrrole-Dopamine Nanofiber Light-Trapping Coating for Efficient Solar Vapor Generation

Solar vapor generation (SVG) typically uses a solar absorbing material at the water-air interface to convert solar energy into heat for evaporation. However, the intrinsic solar absorption of the material determines the upper limit of the solar energy capture. By designing a light-trapping surface structure with open pores and channels, we can break this limit and further improve the absorption by enabling multiple reflections within the surface. Polypyrrole (PPy) is emerging as a promising solar thermal material. In this work, we propose an ultrasonic spray coating method to obtain a nanofiber light-trapping coating by copolymerization with dopamine (DA), which can be directly synthesized at room temperature rapidly (30 min). Due to its excellent wettability, this coating can transport water and can be directly coated on the thermal insulating layer, not requiring an additional water transport layer. This nanoscale coating significantly improves solar absorption at different incident angles across the full solar spectrum, achieving the highest solar-to-thermal conversion efficiency of 95.8% at 1.385 kg·m^-2·h^-1 under 1 sun. When applied on salt water, this solar evaporator achieves self-cleaning in the absence of solar irradiation. Moreover, the surface structure can be further tuned into granular/plane-fibrous/plane-granular structures by using different oxidants or surfactants, and their formation mechanisms are also proposed. This PPy-DA nanofiber coating shows great potential for SVG and other applications based on a PPy material, especially for those requiring a certain surface morphology.

Tunable, conductive, self-healing, adhesive and injectable hydrogels for bioelectronics and tissue regeneration applications

Conductive hydrogels are attracting considerable interest in view of their potential in a wide range of applications that include healthcare and electronics. Such hydrogels are generally incorporated with conductive materials/polymers. Herein, we present a series of conductive hydrogels (Ch-CMC-PDA), prepared with no additional conductive material. The hydrogels were synthesized using a combination of chitosan, cellulose (CMC) and dopamine (DA). The conductivity (0.01-3.4 × 10^-3 S cm^-1) in these gels is attributed to ionic conductivity. Very few conductive hydrogels are endowed with additional properties like injectability, adhesiveness and self-healing, which would help to widen their scope for applications. While the dynamic Schiff base coupling in our hydrogels facilitated self-healing and injectable properties, polydopamine imparted tissue adhesiveness. The porosity, rheological, mechanical and conductive properties of the hydrogels are regulated by the CMC-dialdehyde-polydopamine (CMC-D-PDA) content. The hydrogel was evaluated in various bioelectronics applications like ECG monitoring and triboelectric nanogenerators (TENG). The ability of the hydrogel to support cell growth and serve as a template for tissue regeneration was confirmed using in vitro and in vivo studies. In summary, the integration of such remarkable features in the ionic-conductive hydrogel would enable its usage in bioelectronics and biomedical applications.

Facile preparation of stretchable and self-healable conductive hydrogels based on sodium alginate/polypyrrole nanofibers for use in flexible supercapacitor and strain sensors

A series of multifunctional conductive hydrogels (denoted as SA-B-DAPPy) is developed by combining sodium alginate (SA) and dopamine functionalized polypyrrole (DAPPy) nanofibers with borax as a cross-linking agent. By modulation of the DAPPy weight ratio to 3.5 wt%, the conductivity of the hydrogel can reach a high value of 1.33 ± 0.012 S/m. Both borate interactions and hydrogen bonds within hydrogel frameworks can account for the satisfactory stretchability (more than 800%) and instantaneous self-healing ability. More significantly, the SA-B-DAPPy hydorgels can be easily fabricated as electrode component in the symmetric supercapacitor with SA-B-DAPPy//SA-B//SA-B-DAPPy configuration. Due to the self-healing of the electrode/electrolyte interface, the obtained all-in-one device can deliver superior areal specific capacitance of 587 mF/cm² at current density of 1.0 mA/cm², high energy density of 52.18 μWh/cm² at power density of 800 μW/cm², good capacitance retention of 80% after 2000 cycles, as well as integration characteristics. Furthermore, on account of high conductivity, a thin SA-B-DAPPy hydrogel film can be fabricated into the motion sensor to detect and distinguish various human movements. The sensor exhibits high gauge factor (GF) up to 10.23, and stable, repeatable response signals, which permit supersensitive for monitoring large-scale joints motions and subtle muscle movements.

The Bioactive Polypyrrole/Polydopamine Nanowire Coating with Enhanced Osteogenic Differentiation Ability with Electrical Stimulation

Polypyrrole (PPy) is a promising conducting polymer in bone regeneration; however, due to the biological inertia of the PPy surface, it has poor cell affinity and bioactivity. Based on the excellent adhesion capacity, biocompatibility, and bioactivity of polydopamine (PDA), the PDA is used as a functional coating in tissue repair and regeneration. Herein, we used a two-step method to construct a functional conductive coating of polypyrrole/polydopamine (PPy/PDA) nanocomposite for bone regeneration. PPy nanowires (NWs) are used as the morphologic support layer, and a layer of highly bioactive PDA is introduced on the surface of PPy NWs by solution oxidation. By controlling the depositing time of PDA within 5 h, the damage of nano morphology and conductivity of the PPy NWs caused by the coverage of PDA deposition layer can be effectively avoided, and the thin PDA layer also significantly improve the hydrophilicity, adhesion, and biological activity of PPy NWs coating. The PPy/PDA NWs coating performs better biocombaitibility and bioactivity than pure PPy NWs and PDA, and has benefits for the adhesion, proliferation, and osteogenic differentiation of MC3T3-E1 cells cultured on the surface. In addition, PPy/PDA NWs can significantly promote the osteogenesis of MC3T3-E1 in combination with micro galvanostatic electrical stimulation (ES).

Electro-responsive controlled drug delivery from melanin nanoparticles

Electro-responsive controlled drug delivery has been receiving an increasing interest as one of the on-demand drug delivery systems, aiming the improvement of the therapeutics efficacy by controlling the amount of drug release at a specific time and target site. Herein, we report a simple method to develop an electro-responsive controlled drug delivery system using functionalized melanin nanoparticles (FMNPs) with polydopamine and polypyrrole to precisely control the release of dexamethasone (Dex). Optimized FMNPs showed 376.77 ± 62.05 nm of particle size, a polydispersity index of 0.26 ± 0.09 and a zeta-potential (ZP) of -32.59 ± 3.61 mV. FMNPs evidenced a spherical shape, which was confirmed by scanning electron microscopy. Fourier-transform infrared spectrometry analysis confirmed the deposition of the polymers on the FMNPs' surface. The incorporation efficiency of the optimized Dex-loaded FMNPs was 94.45 ± 0.63% and the increase of ZP to -40.34 ± 4.65 mV was attributed to the anionic nature of Dex. In vitro Dex release studies without stimuli revealed a maximum Dex release below 10%. Applying electrical stimulation, Dex release was augmented, with a maximum of ca. 32% after 24 h. The designed FMNPs provide a powerful biomaterial-based technological tool for electro-responsive controlled drug delivery, capable of surpassing the associated lack of efficiency and stability of current carriers.

Sustainable Battery Materials from Biomass

Sustainable sources of energy have been identified as a possible way out of today's oil dependency and are being rapidly developed. In contrast, storage of energy to a large extent still relies on heavy metals in batteries. Especially when built from biomass-derived organics, organic batteries are promising alternatives and pave the way towards truly sustainable energy storage. First described in 2008, research on biomass-derived electrodes has been taken up by a multitude of researchers worldwide. Nowadays, in principle, electrodes in batteries could be composed of all kinds of carbonized and noncarbonized biomass: On one hand, all kinds of (waste) biomass may be carbonized and used in anodes of lithium- or sodium-ion batteries, cathodes in metal-sulfur or metal-oxygen batteries, or as conductive additives. On the other hand, a plethora of biomolecules, such as quinones, flavins, or carboxylates, contain redox-active groups that can be used as redox-active components in electrodes with very little chemical modification. Biomass-based binders can replace toxic halogenated commercial binders to enable a truly sustainable future of energy storage devices. Besides the electrodes, electrolytes and separators may also be synthesized from biomass. In this Review, recent research progress in this rapidly emerging field is summarized with a focus on potentially fully biowaste-derived batteries.

Controlling Long-Distance Photoactuation with Protein Additives

Long-distance wireless actuation indicates precise remote control over materials, sensors, and devices that are widely utilized in biomedical, defence, disaster relief, deep ocean, and outer space applications to replace human work. Unlike radio frequency (RF) control, which has low tolerance toward electromagnetic interference (EMI), light control represents a promising method to overcome EMI. Nonetheless, long-distance light-controlled wireless actuation able to compete with RF control has not been achieved until now due to the lack of highly light-sensitive actuator designs. Here, it is demonstrate that amyloid-like protein aggregates can organize photomodule single-layer reduced graphene oxide (rGO) into a well-defined multilayer stack to display long-distance photoactuation. The amyloid-like proteinaceous component docks the rGO layers together to form a hybrid film, which can reliably adhere onto various material surfaces with robust interfacial adhesion. The sensitive photothermal effect and a fast bending in 1 s to switch a circuit are achieved after forming the film on a plastic substrate and irradiating the bilayer film with a blue laser from 100 m away. A photoactuation distance of 50 km can be further extrapolated based on a commercial high-power laser. This study reveals the great potential of amyloid-like aggregates in remote light control of robots and devices.

Three-dimensional directional nerve guide conduits fabricated by dopamine-functionalized conductive carbon nanofibre-based nanocomposite ink printing

Directional growth induced by dopamine-functionalized CNF-based nanocomposite ink printing.

An Injectable Conductive Three-Dimensional Elastic Network by Tangled Surgical-Suture Spring for Heart Repair

Designing scaffolds with persistent elasticity and conductivity to mimic microenvironments becomes a feasible way to repair cardiac tissue. Injectable biomaterials for cardiac tissue engineering have demonstrated the ability to restore cardiac function by preventing ventricular dilation, enhancing angiogenesis, and improving conduction velocity. However, limitations are still among them, such as poor mechanical stability, low conductivity, and complicated procedure. Here, we developed thermal plastic poly(glycolic acid) surgical suture and mussel-inspired conductive particle's adhesion into a highly elastic, conductive spring-like coils. The polypyrrole (PPy)-coated biospring acted as an electrode and then was assembled into a solid-state supercapacitor. After being injected through a syringe needle (0.33 mm inner diameter), the tangled coils formed an elastically conductive three-dimensional (3-D) network to modulate cardiac function. We found that cardiomyocytes (CMs) grew along the spring coils' track with elongated morphologies and formed highly oriented sarcomeres. The biospring enhanced the CMs' maturation in synchronous contraction accompanied by high expressions of cardiac-specific proteins, α-actinin, and connexin 43 (cx43). After the elastic, conductive biosprings were injected into the myocardial infarction (MI) area, the left ventricular fractional shortening was improved by about 12.6% and the infarct size was decreased by about 34%. Interestingly, the spring can be utilized as a sensor to measure the CMs' contractile force, which was 1.57 × 10^-3 ± 0.26 × 10^-3 mN (∼4.1 × 10⁶ cells). Accordingly, this study highlights an injectable biospring to form a tangled conductive 3-D network in vivo for MI repair.

Allylamine PECVD Modification of PDMS as Simple Method to Obtain Conductive Flexible Polypyrrole Thin Films

In this paper, we report a one-step method to obtain conductive polypyrrole thin films on flexible substrates. To do this, substrates were modified through allylamine plasma grafting to create a high amount of reactive amine groups on PDMS surface. These groups are used during polypyrrole particle synthesis as anchoring points to immobilize the polymeric chains on the substrate during polymerization. Surface morphology of polypyrrole thin films are modified, tailoring the polyelectrolyte used in the polypyrrole synthesis obtaining different shapes of nanoparticles that conform to the film. Depending on the polyelectrolyte molecular weight, the shape of polypyrrole particles go from globular (500 nm diameter) to a more constructed and elongated shape. The films obtained with this methodology reflected great stability under simple bending as well as good conductivity values (between 2.2 ± 0.7 S/m to 5.6 ± 0.2 S/cm).

Dual surface modification of carbon materials by polydopamine and phosphomolybdic acid for supercapacitor application

Surface modification of carbon materials is an important issue for its potential application. In this work, this purpose has been successfully achieved by the incorporation of polydopamine (PDA) and phosphomolybdic acid (PMA), forming carbon/PDA/PMA hybrid electrode materials, in which PDA acts both as a linker molecule and as a pseudo-capacitance provider, and PMA contributes to pseudo-capacitive performance. It is revealed that adding PDA and/or PMA results in a decrease of porosity but in an increase of electrical conductivity and thus a suitable combination of porosity, conductivity, and pseudo-capacitance is vital for achieving the optimization of capacitive performance. By using the Trasatti method, we found out that increasing PDA or PMA results in the improvement of pseudo-capacitance proportion and the C-PDA/PMA-1 : 1 sample exhibits a pseudo-capacitance proportion of 32%. In a two-electrode configuration, the C-PDA/PMA-1 : 1 sample delivers a specific capacitance of 101 F g-1 at 1 A g-1, a cycling performance of 108% within 10 000 cycles, and an energy density of 3.5 W h kg-1 (nearly 3.2 times that of the C-blank sample) at 500 W kg-1. Moreover, the dual surface modification of PDA and PMA could be extended to other energy storage systems, highly improving capacitive performance by the synergic effect.

Bandgap Engineered Polypyrrole-Polydopamine Hybrid with Intrinsic Raman and Photoacoustic Imaging Contrasts

Intrinsically multimodal nanomaterials have revealed their great potential as a new class of contrast agents. We herein report a bandgap engineering strategy to develop an intrinsically Raman-photoacoustic (PA) active probe that is based on semiconducting conjugated polymers. This dual modal probe is prepared by doping a semiconducting conjugated polymer with polydopamine (PDA) through a one-pot reaction. When applied in the polypyrrole (PPy), this strategy can enhance Raman scattering and the PA amplitude of PPy-PDA hybrid by 3.2 and 2.4 times, respectively, so that both signals can be further applied in bioimaging. In the hybrid, such a dual-enhancement effect is achieved by infusing these two macromolecules at the nanoscale to reduce the optical bandgap energy. This work not only introduces a dual modal contrast agent but also provides a new method of manipulating semiconducting polymer's inherent optical features for bioimaging.

Dual Colorimetric and Conductometric Responses of Silver-Decorated Polypyrrole Nanowires for Sensing Organic Solvents of Varied Polarities

We report on the discovery of an interesting dual colorimetric and conductometric response of synthesized water-based silver-decorated polypyrrole (Ag/PPy) nanowire to organic solvents, and the possible fabrication of a volatile organic compounds (VOCs) sensor based on the stimuli-responsive Ag/PPy nanocomposites. The dual-responsive nature of this material allows for a straightforward way to differentiate various VOCs within a broad polarity range by noncontact optical means via color transition, but also can provide highly accurate quantitative identification of each VOC by electronic detection.

Attenuated Glial Reactivity on Topographically Functionalized Poly(3,4-Ethylenedioxythiophene):P-Toluene Sulfonate (PEDOT:PTS) Neuroelectrodes Fabricated by Microimprint Lithography

Following implantation, neuroelectrode functionality is susceptible to deterioration via reactive host cell response and glial scar-induced encapsulation. Within the neuroengineering community, there is a consensus that the induction of selective adhesion and regulated cellular interaction at the tissue-electrode interface can significantly enhance device interfacing and functionality in vivo. In particular, topographical modification holds promise for the development of functionalized neural interfaces to mediate initial cell adhesion and the subsequent evolution of gliosis, minimizing the onset of a proinflammatory glial phenotype, to provide long-term stability. Herein, a low-temperature microimprint-lithography technique for the development of micro-topographically functionalized neuroelectrode interfaces in electrodeposited poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (PEDOT:PTS) is described and assessed in vitro. Platinum (Pt) microelectrodes are subjected to electrodeposition of a PEDOT:PTS microcoating, which is subsequently topographically functionalized with an ordered array of micropits, inducing a significant reduction in electrode electrical impedance and an increase in charge storage capacity. Furthermore, topographically functionalized electrodes reduce the adhesion of reactive astrocytes in vitro, evident from morphological changes in cell area, focal adhesion formation, and the synthesis of proinflammatory cytokines and chemokine factors. This study contributes to the understanding of gliosis in complex primary mixed cell cultures, and describes the role of micro-topographically modified neural interfaces in the development of stable microelectrode interfaces.

Construction of Metal-Organic Framework/Conductive Polymer Hybrid for All-Solid-State Fabric Supercapacitor

Metal-organic frameworks (MOFs) hold promising potential in energy storage but are limited by poor conductivity. In this work, a metal-organic framework/polypyrrole hybrid is constructed by a facile one-pot electrodeposition method in the presence of dopamine. An all-solid-state fabric supercapacitor based on this hybrid demonstrates excellent electrochemical energy-storage performance, which achieves a specific capacitance of 10 mF cm^-1 (206 mF cm^-2), a power density of 132 μW cm^-1 (2102 μW cm^-2), and an energy density of 0.8 μWh cm^-1 (12.8 μWh cm^-2). The stable cycling life and excellent mechanical flexibility over a wide range of working temperature are also achieved, which maintains a capacitance retention of 89% over 10 000 charging/discharging cycles, a capacitance decrease of only 4% after 1000 frizzy (360° bending) cycles, and no obvious capacitance loss under 100 repeated heating (100 °C)/cooling (-15 °C) cycles. This fibrous supercapacitor displays promising potential in wearable textile electronics as it can be easily woven into common cotton cloth. Our strategy may shed some valuable light on the construction of MOF-based hybrids for flexible energy-storage electronics.

Bio-Inspired Polymeric Structures with Special Wettability and Their Applications: An Overview

It is not unusual for humans to be inspired by natural phenomena to develop new advanced materials; such materials are called bio-inspired materials. Interest in bio-inspired polymeric superhydrophilic, superhydrophobic, and superoleophobic materials has substantially increased over the last few decades, as has improvement in the related technologies. This review reports the latest developments in bio-inspired polymeric structures with desired wettability that have occurred by mimicking the structures of lotus leaf, rose petals, and the wings and shells of various creatures. The intrinsic role of surface chemistry and structure on delivering superhydrophilicity, superhydrophobicity, and superoleophobicity has been extensively explored. Typical polymers, commonly used structures, and techniques involved in developing bio-inspired surfaces with desired wettability are discussed. Additionally, the latest applications of bio-inspired structures with desired wettability in human activities are also introduced.

Easily fabricated and lightweight PPy/PDA/AgNW composites for excellent electromagnetic interference shielding

Conductive polymer composites (CPCs) containing nanoscale conductive fillers have been widely studied for their potential use in various applications. In this paper, polypyrrole (PPy)/polydopamine (PDA)/silver nanowire (AgNW) composites with high electromagnetic interference (EMI) shielding performance, good adhesion ability and light weight are successfully fabricated via a simple in situ polymerization method followed by a mixture process. Benefiting from the intrinsic adhesion properties of PDA, the adhesion ability and mechanical properties of the PPy/PDA/AgNW composites are significantly improved. The incorporation of AgNWs endows the functionalized PPy with tunable electrical conductivity and enhanced EMI shielding effectiveness (SE). By adjusting the AgNW loading degree in the PPy/PDA/AgNW composites from 0 to 50 wt%, the electrical conductivity of the composites greatly increases from 0.01 to 1206.72 S cm^-1, and the EMI SE of the composites changes from 6.5 to 48.4 dB accordingly (8.0-12.0 GHz, X-band). Moreover, due to the extremely low density of PPy, the PPy/PDA/AgNW (20 wt%) composites show a superior light weight of 0.28 g cm^-3. In general, it can be concluded that the PPy/PDA/AgNW composites with tunable electrical conductivity, good adhesion properties and light weight can be used as excellent EMI shielding materials.

Electrochemical deposition of conductive and adhesive polypyrrole-dopamine films

Electrode surfaces have been widely modified with electrically conductive polymers, including polypyrrole (PPY), to improve the performance of electrodes. To utilize conductive polymers for electrode modification, strong adhesion between the polymer films and electrode substrates should be ensured with high electrical/electrochemical activities. In this study, PPY films were electrochemically polymerized on electrodes (e.g., indium tin oxide (ITO)) with dopamine as a bio-inspired adhesive molecule. Efficient and fast PPY electrodeposition with dopamine (PDA/PPY) was found; the resultant PDA/PPY films exhibited greatly increased adhesion strengths of up to 3.7 ± 0.8 MPa and the modified electrodes had electrochemical impedances two to three orders of magnitude lower than that of an unmodified electrode. This electrochemical deposition of adhesive and conductive PDA/PPY offers a facile and versatile electrode modification for various applications, such as biosensors and batteries.

Free-Standing, Nanopatterned Janus Membranes of Conducting Polymer-Virus Nanoparticle Arrays

Nanostructured mesoscale materials find wide-ranging applications in medicine and energy. Top-down manufacturing schemes are limited by the smallest dimension accessible; therefore, we set out to study a bottom-up approach mimicking biological systems, which self-assemble into systems that orchestrate complex energy conversion functionalities. Inspired by nature, we turned toward protein-based nanoparticle structures formed by plant viruses, specifically the cowpea mosaic virus (CPMV). We report the formation of hierarchical CPMV nanoparticle assemblies on colloidal-patterned, conducting polymer arrays using a protocol combining colloidal lithography, electrochemical polymerization, and electrostatic adsorption. In this approach, a hexagonally close-packed array of polystyrene microspheres was assembled on a conductive electrode to function as the sacrificial colloidal template. A thin layer of conducting polypyrrole material was electrodeposited within the interstices of the colloidal microspheres and monitored in situ using electrochemical quartz crystal microbalance with dissipation (EC-QCM-D). Etching the template revealed an inverse opaline conducting polymer pattern capable of forming strong electrostatic interactions with CPMV and therefore enabling immobilization of CPMV on the surface. The CPMV-polymer films were characterized by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). Furthermore, molecular probe diffusion experiments revealed selective ion transport properties as a function of the presence of the CPMV nanoparticles on the surface. Lastly, by utilizing its electromechanical behavior, the polymer/protein membrane was electrochemically released as a free-standing film, which can potentially be used for developing high surface area cargo delivery systems, stimuli-responsive plasmonic devices, and chemical and biological sensors.

Controlled growth of silver nanoparticles on carbon fibers for reinforcement of both tensile and interfacial strength

We have developed an electro-chemical deposition approach to synthesize various structures of Ag NPs on carbon fibers. This improved both the tensile strength and the interfacial property as much as 57.2% and 27.2%, respectively.

Oleophobicity of Biomimetic Micropatterned Surface and Its Effect on the Adhesion of Frozen Oil

The relationship between the oleophobicity of micropatterned surfaces and the reduction of oil adhesion at low temperatures was explored by using siloxane elastomer surfaces as a model system. Polydimethylsiloxane (PDMS) surfaces were fabricated with varying oleophobicity from oleophilic to superoleophobic by combing the blending of trichloro(1H,1H,2H,2H-perfluorooctyl)silane (FDTS) into PDMS with the construction of bioinspired micropillars. The oil contact angles of micropillars were >130°, with the largest contact angle measured to be 146°. The micropillared surface showed remarkable self-cleaning properties; the contact angle hysteresis was <15°. The transparent oil droplets on PDMS surfaces of varied oleophobicity were frozen into a white-colored solid at -25 °C with the aid of a cooling system. Adhesion forces of the frozen oil droplets were obtained from the knock-off tests, showing that the adhesion forces dropped with the increased oleophobicity. The largest adhesion force was observed on the oleophilic flat surface, while the lowest adhesion force was on the highest oleophobic micropillared surface. The relative effectiveness of chemical and physical modifications on adhesion strength reduction was studied in terms of FDTS and micropillars, respectively. The results showed that a reduction of adhesion strength by 4% was reached by blending FDTS into flat PDMS, while a much more pronounced reduction of frozen oil adhesion strength by 60% was achieved by blending FDTS into PDMS micropillars; these results suggested a possible synergic effect of the FDTS chemistry and micropillar on the reduction of adhesion strength of frozen oil droplets.

A sweet polydopamine nanoplatform for synergistic combination of targeted chemo-photothermal therapy

Inspired by sweet or sugar-coated bullets that are used for medications in clinics and the structure and function of biological melanin, a novel kind of sweet polydopamine nanoparticles and their anticancer drug doxorubicin loaded counterparts are prepared, which integrate an active targeting function, photothermal therapy, and chemotherapy into one polymeric nanocarrier. The oxidative polymerization of lactosylated dopamine and/or with dopamine are performed under mild conditions and the resulting sweet nanoparticles are thoroughly characterized. When exposed to an 808 nm continuous-wave diode laser, the magnitude of temperature elevation not only increases with the concentration of nanoparticles, but can also be tuned by the laser power density. The nanoparticles possess strong near infrared light absorption, high photothermal conversion efficiency, and good photostability. The nanoparticles present tunable binding with RCA120 lectin and a targeting effect to HepG2 cells, confirmed by dynamic light scattering, turbidity analysis, MTT assay, and flow cytometry. Importantly, the sweet nanoparticles give the lowest IC50 value of 11.67 μg mL(-1) for chemo-photothermal therapy compared with 43.19 μg mL(-1) for single chemotherapy and 67.38 μg mL(-1) for photothermal therapy alone, demonstrating a good synergistic effect for the combination therapy.

Facilely tuning the bioactivity of an orthopedic implant surface based on nanostructured polypyrrole/glycosaminoglycans

The wettability of nanostructured polypyrrole/glycosaminoglycans can be controlled in situ by electrical stimulus to tune the bioactivity of implants.