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A Na-doped iridium oxide film is heterogeneously deposited on ITO. Time-resolved XAS validates the sequential oxidative–reductive steps for the Ir3+ precursor. The film exhibits an impressive electrochemical performance and a negligible bio-toxicity.

A Na–IrOx(OH)y cell using body fluid as the electrolyte demonstrates large charge storage capacity and long lifetime.

Surface-enhanced Raman scattering (SERS) has been a useful sensing technique, in which inelastic light scattering can be significantly enhanced by absorbing molecules onto rough metal surfaces or nanoparticles. Although many methods have been developed to prepare SERS substrates, it is still highly desirable and challenging to design SERS substrates, especially with highly ordered and controlled three-dimensional (3D) structures. In this work, we develop novel SERS substrates with regular volcano-shaped polymer structures using the versatile solvent on-film annealing method. Polystyrene (PS) nanospheres are first synthesized by surfactant-free emulsion polymerization and assembled on poly(methyl methacrylate) (PMMA) films. After annealing in acetic acid vapors, PMMA chains are selectively swollen and wet the surfaces of the PS nanospheres. By selectively removing the PS nanospheres using cyclohexane, volcano-shaped PMMA films can be obtained. Compared with flat PMMA films with water contact angles of ∼74°, volcano-shaped PMMA films exhibit higher water contact angles of ∼110° due to the sharp features and rough surfaces. The volcano-shaped PMMA films are then coated with gold nanoparticles (AuNPs) as SERS substrates. Using rhodamine 6G as the probe molecules, the SERS results show that the Raman signals of the volcano-shaped PMMA/AuNP hybrid substrates are much higher than those of the pristine PMMA films and PMMA films with AuNPs. For the volcano-shaped PMMA/AuNP hybrid substrates using 400 nm PS nanospheres, a high enhancement factor (EF) value of ∼1.12 × 10

We demonstrate the fabrication of a flexible and conductive bioelectrode via the electrodeposition of IrO2 nanoparticles on a metalized polypropylene micromembrane (PPMM). The metalized PPMM is prepared by carrying out conformal electroless deposition of Au on individual polypropylene (PP) fibers of PPMM using both polydopamine and polyvinyl alcohol as the surface–modifying agents to improve the hydrophilicity of PPMM. Images from scanning and transmission electron microscopes, as well as analysis from energy dispersive X–ray spectrometer and X–ray photoelectron spectroscopy confirm the successful formation of IrO2 nanoparticles on individual PP fibers of metalized PPMM. For bio–stimulating purpose, the IrO2–coated PPMM reveals an impressive charge–storage–capacity of 54.6 mC/cm2 in cyclic voltammetry, In addition, under a symmetric bi–phasic current pulse, its charge–injection–capacity reaches 466 μC/cm2. Since the entire constituents for the IrO2–coated PPMM are bio−compatible, we envision its potential use as a bioelectrode in implantable biomedical devices.

A chitosan composite with a vertical array of pore channels is fabricated via an electrophoretic deposition (EPD) technique. The composite consists of chitosan and polyethylene glycol, as well as nanoparticles of silver oxide and silver. The formation of hydrogen bubbles during EPD renders a localized increase of hydroxyl ions that engenders the precipitation of chitosan. In addition, chemical interactions among the constituents facilitate the establishment of vertical channels occupied by hydrogen bubbles that leads to the unique honeycomb-like microstructure; a composite with a porosity of 84%, channel diameter of 488 µm, and channel length of 2 mm. The chitosan composite demonstrates an impressive water uptake of 2100% and a two-stage slow release of silver. In mass transport analysis, both Disperse Red 13 and ZnO powders show a much enhanced transport rate over that of commercial gauze. Due to its excellent structural integrity and channel independence, the chitosan composite is evaluated in a passive suction mode for an adhesive force of 9.8 N (0.56 N cm

The development of eco-friendly and light-weighted solid-state electrolytes with a wide electrochemical window is critical to apply flexible energy storage devices for powering wearable and implantable electronics. Herein, we report the first demonstration of a quasi solid-state hydrogel electrolyte leveraging the formation of “interfacial wetting water” for facile two-dimensional ion transports instead of typical diffusion in bulk-like water. The hydrogel electrolyte exhibits a wide electrochemical window (2.5 V) in electrical double layer capacitance (EDLC) cell with an extremely effective low salt concentration (6.8 m), 3.1 times lower than the well-known water-in-salt electrolyte (WiSE, 21 m), and a small water retention (24 wt%). Besides, a significant toughness (ultimate tensile strength of 420 kPa and elongation of 6,000%) is achieved. The flexible supercapacitor demonstrates the high specific energy density of 39.1 Wh•kg−1 at 0.5 A•g−1 and 7.6 Wh•kg−1 at power density of 6218 W•kg−1, as well as a subdued self-discharge profile. This interfacial water dominated hydrogel electrolyte provides new directions in designing high-voltage hydrogel electrolyte for safe and sustainable soft energy storage devices.

We demonstrate a facile and seedless wet chemical process to deposit RuO2 thin film on a glass slide. The process entails the use of dopamine and its oxidized form, polydopamine (PDA), as the reducing and chelating agent, as well as the adhesive agent bonding the RuO2 and glass slide. The formula starts with the oxidation of K2RuCl5 to prepare RuO4 solution, followed by its reduction by dopamine to form chelated RuO2 colloids for the deposition of amorphous RuO2 thin film containing 26.5 at% hydrous RuO2 and 73.5 at% RuO2. After a mild Ar annealing, the RuO2 thin film exhibits a rutile phase with (110) preferred orientation. Elemental analysis indicates incomplete pyrolysis of PDA. Results from X-ray absorption spectroscopy confirm the presence of RuO4 and its transformation to RuO2. Electrochemical analysis of the adsorbed dopamine molecules on an ITO substrate validates the oxidative behavior of dopamine. The bonding strength of RuO2 thin film is determined by a tape-peeling test in which both the as-deposited and annealed RuO2 thin films show robust adhesion to the glass substrate.

A three-dimensional ordered macroporous Cu2O/Ni structure is fabricated by pulse electrodeposition of Cu2O nanoparticles on the skeletons of Ni inverse opals, and evaluated for electrochemical sensing of glucose. In the composite Cu2O/Ni structure, the Cu2O is primarily responsible for chemical sensing whereas the Ni inverse opals serve as the current collector providing an open framework for large accessible area and facile mass transport. Comprehensive material characterization and electrochemical analysis are conducted. For glucose sensing in a 0.1 M aqueous KOH solution, the composite Cu2O/Ni structure demonstrates comparable or even better performances than nanostructured Cu2O counterparts reported in the literatures. The Cu2O/Ni structure exhibits a linear detection range between 10 and 4970 µM, a low detection limit of 3.82 µM, as well as a sensitivity of 450.7 μA/(mM cm2) at 0.5 V.

An effective solution-based process is developed for the fabrication of iridium oxide thin film in application of bio-stimulating electrode. The chemical bath employs a pre-coordination scheme in which the IrCl63− precursor undergoes a ligand exchange step to form stable Ir(OH)63−, followed by an oxidative electroless deposition to render iridium oxide thin film with desirable surface morphologies. Relevant processing parameters have been optimized to increase the utilization rate of Ir precursor for a thicker deposit without any noticeable defect. The iridium oxide thin film is mechanically robust and exhibits superior performances in both charge storage capacity and charge injection capacity. In particular, the normalized charge storage capacity is recorded at 0.367 mC/(cm2˙nm), a value that is five times greater than comparable iridium oxide thin films. In addition, in cell viability test, the iridium oxide thin film demonstrates impressive biocompatibility with desirable growth of neuronal cells.

Silk fibroin (SF) is recognized for its rich nitrogen content and has been explored for its promising potential in energy storage because of its hexagonal pseudographitic structure from the direct ...

We demonstrate a composite approach to improve the mechanical strength of nanostructured Ni foams by producing a conformal coating of TiO2 on the skeletons of the Ni foam. The nanostructured Ni foam is fabricated by a template approach in which colloidal crystals of polystyrene microspheres in 720 nm diameter are constructed by a vertical electrophoresis process, followed by electroplating of Ni to fill the interstitial voids among the closely-packed microspheres and removal of the colloidal template afterward. The formation of TiO2 overcoat is achieved by optimization of sol-gel synthesis to prepare desirable TiO2 sols and their subsequent electrophoresis toward the nanostructured Ni foam in a square wave pulsing mode. The thickness of the TiO2 deposit is proportional to the duration of pulsing electrophoresis. From nano-indentation, the TiO2-coated nanostructured Ni foams exhibit notable improvements in hardness (53–68%) and reduced elastic modulus (26–37%) over those of pristine nanostructured Ni foams. This strategy of implementing a thin ceramic overcoat provides an effective mean to improve the mechanical properties of nanostructured metals.

An optimized mixture of polydopamine (PDA) and polyvinyl alcohol (PVA) is employed as the surface functionalizing agent and reducing agent to encapsulate individual polypropylene (PP) fibers of polypropylene micromembrane (PPMM). The functionalized PPMM becomes hydrophilic to allow the formation of Au nuclei for subsequent electroless Au deposition. The metalized PPMM is further deposited with IrO

We developed implementation technologies for artificial vision devices compatible with suprachoroidal transretinal stimulation. We aimed to develop a device that can be safely implanted in the sclera of the eye for a long period. Using parylene C and bioceramics as biocompatible base materials, we realized a device with high in vivo safety by making the device structure flexible and reducing the wires of control signals. We successfully created a prototype device that combines a flexible wire structure based on a parylene C thin film with a wire-saving CMOS smart electrode structure based on CMOS integrated circuits. We conducted in vitro and in vivo experiments to confirm their performances. The immersion test confirmed that the device could work normally for four days. Furthermore, in the in vivo experiments using rats, we successfully measured evoked potentials in the brain induced by the stimulation current using the device.

Inverse opals are three-dimensional ordered macroporous materials whose pores are arranged in a hexagonal array with interconnected pore channels. These unique structural attributes provide an excessive surface area with facile mass transport. In this work, we fabricate a composite NiCoO2/NiCo2O4 thin layer encapsulating the skeletons of Ni inverse opals serving as the conductive substrate, and explore their electrocatalytic activities for the oxygen evolution reaction (OER) in an alkaline electrolyte. The NiCoO2/NiCo2O4 inverse opals are prepared by electroplating of NiCo alloy on Ni inverse opals followed by a mild oxidation treatment in air at 200 °C for 20 min. The X-ray diffraction patterns indicate mixed phases of crystalline NiCoO2, NiCo2O4, and NiCo, and images from scanning electron microscopy demonstrate the conformal formation of NiCoO2/NiCo2O4/NiCo on the Ni inverse opaline skeletons. Analysis from X-ray photoelectron spectroscopy determines the oxidation states for surface Co and Ni ions to be both +2 and +3. Electrochemical measurements including the active surface area and OER performance reveal a large surface area and strong OER activity with a relatively flat Tafel slope of 95 mV dec−1. In addition, from durability tests in both galvanostatic and potentiostatic modes, the sample shows impressive stability in both profiles while the inverse opaline structure is nicely maintained.

An effective and high-throughput method is demonstrated to produce a colloidal crystal with impressive crystallinity. The fabrication procedure involves a two-stage electrophoresis process in which a vertical electrophoretic deposition of polystyrene microspheres (495 nm) is conducted on an ITO substrate to form a colloidal crystal in size of 4 × 4 cm2, followed by a horizontal electrophoresis to improve the packing crystallinity. Relevant parameters associated with the horizontal electrophoresis step including voltage polarity, bipolar voltage offset, and operation frequency are investigated. Their effects over the crystallinity of the colloidal crystals are verified quantitatively and qualitatively by structural observation via scanning electron microscope and optical reflectance spectra. We determine that the imposition of an alternately-changing bias of 80/0/-120/0 V at 10 Hz (25 ms in each bias) enables the production of colloidal crystals with the largest grain size (106 μm) and the smallest grain boundary (170 nm), as compared to samples prepared from a single vertical electrophoresis step. We attribute the improved crystallinity of the colloidal crystal to the bipolar bias that engenders localized movements of the microspheres, rendering them to pack more closely with reduced defects.

We develop a chemical formulation to synthesize stable IrO 2 colloidal solution as a bio-ink for ink-jet printing purpose. This wet chemical process entails Na 3 IrCl 6 and NaClO as the Ir precursor and oxidizer, respectively. In addition, citric acid and sodium hydroxide are employed as the complex agent and pH adjuster. The pH value of the IrO 2 colloidal solution could be readily adjusted over a broad range without incurring undesirable precipitation. Their respective zeta potential decreases from positive to negative with increasing pH values. The IrO 2 colloidal solution demonstrates impressive chemical stability over extended storage at 5 and 65 °C. Images from transmission electron microscope indicate the average size for the IrO 2 nanoparticles to be 3.5 nm. The X-ray diffraction pattern from the heat-treated IrO 2 sample shows a polycrystalline rutile phase. The IrO 2 colloidal solution undergoes repeated filtering and washing to retrieve the IrO 2 nanoparticles. After an annealing at 450 °C for 2 h in air, the crystalline IrO 2 nanoparticles are resuspended in a 0.5 wt% aqueous medium as the bio-ink for ink-jet printing on an ITO substrate. Our method enables the synthesis of stable IrO 2 nanoparticles in a neutral solution at 25 °C, which provides a facile and effective approach over conventional ones that require alkaline environment at elevated temperature.

We demonstrate a simple scheme to produce dense and adhering IrO2 thin films on ITO substrates via a bipolar pulsing process combining both electrophoresis and electro-flocculation. Our fabrication steps entail the synthesis of negatively-charged IrO2 nanoparticles in size of 3.5 nm using NaClO as an oxidizer in conjunction with Na3IrCl6, citric acid, and NaOH. Subsequently, multiple bipolar potentiostatic pulses are imposed in which alternating positive and negative potentials engender the electrophoresis of IrO2 nanoparticles, followed by their immediate coalescence facilitated by proton-catalyzed electro-flocculation. The resulting IrO2 thin films reveal impressive physical properties in surface uniformity, robust structural integrity, and strong adhesion to the substrate. The as-synthesized IrO2 thin film exhibits an amorphous nature with a pH sensing slope between −73.6 and −71.5 mV/pH, characteristic of super-Nernstian behavior. In contrast, the annealed IrO2 sample demonstrates a crystalline rutile phase with a pH sensing slope between −49.5 and −54.7 mV/pH, consistent with typical Nernstian response. Our approach provides a new route for the formation of strong and adhering oxide films from their colloidal constituents.

We demonstrate the fabrication of free-standing inverse opals with gradient pores via a combination of electrophoresis and electroplating techniques. Our processing scheme starts with the preparation of multilayer colloidal crystals by conducting sequential electrophoresis with polystyrene (PS) microspheres in different sizes (300, 600, and 1000 nm). The critical factors affecting the stacking of individual colloidal crystals are discussed and relevant electrophoresis parameters are identified so the larger PS microspheres are assembled successively atop of smaller ones in an orderly manner. In total, we construct multilayer colloidal crystals with vertical stacking of microspheres in 300/600, 300/1000, and 300/600/1000 nm sequences. The inverse opals with gradient pores are produced by galvanostatic plating of Ni, followed by the selective removal of colloidal template. Images from scanning electron microscopy exhibit ideal multilayer close-packed structures with well-defined boundaries among different layers. Results from porometer analysis reveal the size of bottlenecks consistent with those of interconnected pore channels from inverse opals of smallest PS microspheres. Mechanical properties determined by nanoindentation tests indicate significant improvements for multilayer inverse opals as compared to those of conventional single-layer inverse opals.

We demonstrate a water-based synthetic route to fabricate composite inverse opals for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). Our process involves the conformal deposition of poly(3,4-ethylenedioxythiophene) (PEDOT) and PEDOT/Au on the skeletons of Ni inverse opals via cyclic voltammetric scans (CV) to initiate the electropolymerization of 3,4-ethylenedioxythiophene (EDOT) monomers. The resulting samples, Ni@PEDOT, and Ni@PEDOT/Au inverse opals, exhibit a three-dimensional ordered macroporous platform with a large surface area and interconnected pore channels, desirable attributes for facile mass transfer and strong reaction for analytes. Structural characterization and material/chemical analysis including scanning electron microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy are carried out. The sensing performances of Ni@PEDOT and Ni@PEDOT/Au inverse opals are explored by conducting CV scans with various concentrations of AA, DA, and UA. By leveraging the structural advantages of inverse opals and the selection of PEDOT/Au composite, the Ni@PEDOT/Au inverse opals reveal improved sensing performances over those of conventional PEDOT-based nanostructured sensors.

We demonstrate a facile fabrication scheme for Co3O4@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co3O4 nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co3O4/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co3O4 nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co3O4@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co3O4@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co3O4@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C &gt, Co3O4@Pt &gt, Co3O4. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co3O4@Pt. In addition, the specific activity of Co3O4@Pt is more than two times greater than that of Pt/C.

We demonstrate a facile fabrication scheme for Co3O4@CoO@Co (gradient core@shell) nanoparticles on graphene and explore their electrocatalytic potentials for an oxygen evolution reaction (OER) and an oxygen reduction reaction (ORR) in alkaline electrolytes. The synthetic approach begins with the preparation of Co3O4 nanoparticles via a hydrothermal process, which is followed by a controlled hydrogen reduction treatment to render nanoparticles with radial constituents of Co3O4/CoO/Co (inside/outside). X-ray diffraction patterns confirm the formation of crystalline Co3O4 nanoparticles, and their gradual transformation to cubic CoO and fcc Co on the surface. Images from transmission electron microscope reveal a core@shell microstructure. These Co3O4@CoO@Co nanoparticles show impressive activities and durability for OER. For ORR electrocatalysis, the Co3O4@CoO@Co nanoparticles are subjected to a galvanic displacement reaction in which the surface Co atoms undergo oxidative dissolution for the reduction of Pt ions from the electrolyte to form Co3O4@Pt nanoparticles. With commercial Pt/C as a benchmark, we determine the ORR activities in sequence of Pt/C > Co3O4@Pt > Co3O4. Measurements from a rotation disk electrode at various rotation speeds indicate a 4-electron transfer path for Co3O4@Pt. In addition, the specific activity of Co3O4@Pt is more than two times greater than that of Pt/C.

Electrophoresis of chitosan and its composites are widely used to form a coating on selective substrates, but the parasitic water electrolysis causes structural defects that weaken the resulting film. In this work, we demonstrate a bipolar electrophoresis technique that leverages the water electrolysis to produce a chitosan film with less porosity and surface cavities. The process involves a negative bias to deposit the protonated chitosan molecules from the solution, followed by a positive bias to remove the entrapped hydrogen bubbles via the re-protonation of chitosan deposit. Since water electrolysis occurs for both positive and negative bias, the bipolar profile is designed to engender pH changeup near the electrode for "surface conditioning" of chitosan film. The bipolar electrophoresis route demonstrates better coulomb efficiency than that of conventional potentiostatic electrophoresis, resulting in a free-standing chitosan film with sufficient mechanical strength and large area.

A remote optogenetic device for analyzing freely moving animals has attracted extensive attention in optogenetic engineering. In particular, for peripheral nerve regions, a flexible device is needed to endure the continuous bending movements of these areas. Here, a remote optogenetic optical transducer device made from a gold inverse opaline skeleton grown with a dendrite-like gold nanostructure (D-GIOF) and chemically grafted with upconversion nanoparticles (UCNPs) is developed. This implantable D-GIOF-based transducer device can achieve synergistic interaction of the photonic crystal effect and localized surface plasmon resonance, resulting in considerable UCNP conversion efficiency with a negligible thermal effect under low-intensity 980 nm near-infrared (NIR) light excitation. Furthermore, the D-GIOF-based transducer device exhibits remarkable emission power retention (≈100%) under different bending states, indicating its potential for realizing peripheral nerve stimulation. Finally, the D-GIOF-based transducer device successfully stimulates neuronal activities of the sciatic nerve in mice. This study demonstrates the potential of the implantable device to promote remote NIR stimulation for modulation of neural activity in peripheral nerve regions and provides proof of concept for its in vivo application in optogenetic engineering.

Numerous efforts have been attempted to mimic human tongue since years. However they still have limitations because of damages, temperature effects, detection ranges etc. Herein, a self-healable hydrogel-based artificial bioelectronic tongue (E-tongue) containing mucin as a secreted protein, sodium chloride as an ion transporting electrolyte, and chitosan/poly(acrylamide-co-acrylic acid) as the main 3D structure holding hydrogel network was synthesized. This E-tongue is introduced to mimic astringent and bitter mouth feel based on cyclic voltammetry (CV) measurements subjected to target substances, which permits astringent tannic acid (TA) and bitter quinine sulfate (QS) to be detected over wide corresponding ranges of 29.3 mM-0.59 μM and 63.8 mM-6.38 μM with remarkable respective sensitivities of 0.2 and 0.12 wt%−1. Besides, the taste selectivity of this E-tongue is performed in the presence of various mixed-taste chemicals to show its high selective behavior toward bitter and astringent chemicals. The electrical self-healability is shown via CV responses to illustrate electrical recovery within a short time span. In addition, cytotoxicity tests using HeLa cells are performed, where a clear viability of ≥95% verified its biocompatibility. The anti-freezing sensing of E-tongue tastes at −5 °C also makes this work to be useful at sub-zero environments. Real time degrees of tastes are detected using beverages and fruits to confirm future potential applications in food taste detections and humanoid robots.

A composite Cu/MnOx thin film was fabricated by conducting electroplating of Cu and electrophoresis of MnOx colloids simultaneously in an organic electrolyte. The organic electrolyte was prepared by dissolving copper (II) acetylacetonate and manganese (II) acetylacetonate in ethylene glycol, with addition of 10 vol% acetic acid to improve ionic conductivity. Since both Cu ions and MnOx colloids carry positive charges, the formation of a composite film was achieved by a pulse current mode in which a low current pulse was used for Cu2+ reduction, followed by a high current pulse for the electrophoresis of the MnOx colloids. The Cu/MnOx composite film was dense and its X-ray diffraction pattern revealed a mixture of Cu, Mn2O3, and Mn3O4. Both X-ray photoelectron spectroscopy and X-ray absorption spectroscopy show consistent results confirming the metallic nature of Cu and oxidized state of Mn.

This study produces high quality Cu(In,Ga)Se2 (CIGS) solar cells using a two-step process. Stacked In (200 nm)/CuGa (150 ~ 300 nm)/In (500 nm) layers are deposited onto Mo bilayer soda-lime glass by sputtering, using CuGa and In targets, followed by vapor stacking of the elemental Se layers. To produce the CIGS film, the CuGa film is coated in thicknesses of 150, 200, 250 and 300 nm. An appropriate atomic ratio [Cu/(In + Ga), CGI and Ga/(In + Ga), GGI] for the precursors and the CIGS absorption layers composition is easily obtained. Compared to those for the as-deposited precursors, after selenization, the CGI and GGI ratios for CIGS films are almost constant. All CIGS thin films exhibit a peak in the Raman curves at around 173–174 cm−1, which is identified as the CIGS phase. Following sulfurization, the main peaks for CIGS thin films at (112), (220)/(204) and (312)/(116) indicated that the crystalline quaility were improved. The main peaks for the CIGSS films are slightly greater for (112), (220)/(204) and (312)/(116). The band gap energy is increased from 1.19 eV (for the as-grown) to 1.34 eV (for the absorber layer that is sulfurized at 500 °C for 10 min). The performance of the CIGS absorber films is improved by using a proper holding time for sulfurization.

Copper-manganese alloy has been established to improve resistance toward electromigration for interconnects. In this work, we employ a deep eutectic solvent (DES) to formulate a nonaqueous electrolyte for pulse current electrodeposition of Cu-Mn alloyed film. Using impedance spectroscopy to record ionic conductivities of DES-based electrolytes, we determine the optimized bath with a Cu/Mn molar ratio of 1:20. We produce an uniform, smooth, and composition-controllable CuMn alloyed film after exploring various pulsing parameters. Signals from X-ray diffractometer (XRD) suggest successful alloying of Cu and Mn with minor presence of MnO2. Profiles from X-ray photoelectron spectroscopy (XPS) validate the metallic nature of Mn from the as-deposited film. Upon Ar annealing, both XRD and XPS exhibit strong signals of MnO2 formation. In addition, images from transmission electron microscope and qualitative elemental chemical mapping indicate Mn atoms in CuMn alloy either diffuse through the underlying Cu seed layer and segregate at the Cu/SiO2 interface, or migrate toward the external surface forming MnO2.

We develop an alkaline electroless bath for deposition of a conformal Pt layer 40 nm thick on titania nanotubes 800 nm long. The charge storage capacity (CSC) and electrochemically active surface area (ECSA) of this Pt-coated titania nanotube array have been studied to evaluate its potential as a bio-electrode for implantable bio-electronic devices. Images from electron microscopes confirm the formation of a uniform Pt film on both the internal and external surfaces of the nanotubes. The X-ray diffraction pattern indicates a preferred (111) orientation. Analysis from X-ray absorption spectroscopy on the plating bath suggests a reduction sequence of Pt4+ → Pt2+ → Pt. The Pt-coated titania nanotube array has large CSC and ECSA values, attributed to the hollow tubular nanostructure with a conformal Pt coating. Keywords: Titania, Nanotube array, Pt, Electroless deposition, Bio-electrode

We employ a sequential electrophoresis and electrodeposition approach to fabricate a large-area ordered macroporous Ni foam in 5 × 5 cm 2 via a template route. Images from scanning electron microscope exhibit hierarchical structures with hexagonally-arranged pores and interconnected pore channels. For as-prepared and annealed ordered macroporous Ni foams, the loading-depth profiles from nano indentation show typical elastic and plastic deformation. Upon annealing, moderate growth in grain size is observed, resulting in lower hardness and Young’s modulus. In contrast, for disordered macroporous Ni foam and solid Ni film, nano indentation results reveal larger hardness and undetermined Young’s modulus. The ordered macroporous foam reveals hardness that is 22% of that of solid Ni film, a value close to its theoretic packing density of 24%.

Composite Cu2O/Au inverse opals are fabricated by pulse electrodeposition of Cu2O on the skeletons of Au inverse opals, and their H2O2 sensing performances are investigated in a phosphate buffered saline solution. In our composite structure, the Cu2O is responsible for H2O2 sensing, and the Au inverse opals not only contribute to H2O2 sensing but also serve as a current collector providing a large accessible area with interconnected pore channels for facile mass transport. The sensing mechanism of Cu2O and Au complement each other so their simultaneous exposure to H2O2 leads to a larger sensing response. The composite Cu2O/Au inverse opals display a wide linear detection range (5–11,000 µM) and low detection limit (5 µM), as well as a two-stage sensitivity of 304.8 and 60.8 μA/(mM·cm2). In addition, they reveal a relatively low sensing potential (−0.1 V) as compared to alternative nanostructured counterparts. The selectivity and durability of composite Cu2O/Au inverse opals are also validated. The composite Cu2O/Au inverse opals are readily detached from the ITO substrate, rendering a free-standing sample that could accommodate designs for both in-vivo and in-vitro testing.

The film-forming process of chitosan composite films is an important issue because it affects their experimental design, chemicals used, and feasibility of large-scaled fabrication. In this work, electrophoresis is employed to produce chitosan composite films with significantly reduced processing time and environmentally friendly chemicals. With the addition of hydrogen peroxide and polyethylene glycol, the parasitic hydrogen bubble formation during the electrophoresis of chitosan and polydopamine is effectively inhibited that leads to the formation of a defectless chitosan/polyethylene glycol/polydopamine composite film which could be removed from the substrate readily. In addition, the chitosan/polyethylene glycol/polydopamine composite film reveals significantly improved tensile strength and a slower decomposition rate as compared to those of chitosan film and chitosan/polyethylene glycol composite film. This is attributed to the strong interaction between chitosan and polydopamine. Lastly, the chitosan/polyethylene glycol/polydopamine composite film exhibits excellent UV-shielding ability without compromising its visible transparency.

A mixture of polydopamine (PDA) and polyethyleneimine (PEI) are used as the adhesive, wetting, and reducing agent simultaneously to fabricate a conductive silver membrane. The conformal coating of PDA/PEI on individual polypropylene fibers of polypropylene micromembrane (PPMM) renders the latter to be hydrophilic for subsequent electroless silver deposition. The resulting conductive silver membrane demonstrates impressive electric conductivity in both X and Z directions. The thickness of conformal silver overcoat is 250 nm and the effective loading is 2.4 mg/cm2. The mechanical strength of conducive silver membrane is similar to that of pristine PPMM. Both cyclic voltammetry and impedance spectroscopy on the conductive silver membrane reveal a large electrochemical active surface area. To validate its usefulness as a robust soft electrode, the conductive silver membrane is evaluated for the detection of chlorine in aqueous solution in which a low detection limit of 0.07 ppm and a wide detection range of 0.1–20 ppm are validated.

Accumulation of β-amyloid (Aβ) peptides is highly associated with Alzheimer's disease (AD) progression in prevailing studies. The successful development of an ultrasensitive detection assay for Aβ is a challenging task, especially from blood-based samples. Methods: We have developed a one-step electrophoresis/electropolymerization strategy for preparing a CSIP hierarchical immunoelectrochemical interface that is easily integrated into a PoCT device. The interface includes conductive silk fibroin-based immunoparticles (CSIPs) via electropolymerized Poly(3,4-ethylenedioxythiophene) (PEDOT) bridging to enable on-site electrochemical detection of serum amyloid-β42 (Aβ42) and -β40 (Aβ40) peptides from an AD blood test. In addition, micro-positron emission tomography (microPET) neuroimaging and behavioral tests were simultaneously performed. Results: This nanostructured conductive interface favors penetration of water-soluble biomolecules and catalyzes a redox reaction, providing limits of detection (LOD) of 6.63 pg/mL for Aβ40 and 3.74 pg/mL for Aβ42. Our proof-of-concept study confirms that the multi-sensing electrochemical immunosensor array (MEIA) platform enables simultaneous measurement of serum Aβ42 and Aβ40 peptide levels and is more informative in early stage AD animals than amyloid-labeling Aβ plaque PET imaging and behavioral tests. Conclusion: We believe this study greatly expands the applications of silk fibroin-based materials, is an important contribution to the advancement of biomaterials, and would also be valuable in the design of new types of multichannel electrochemical immunosensor arrays for the detection of other diseases.

Long-term operational stability and high-efficiency neuron stimulation are key to the development of retinal prostheses. In this research, a retinal device with a chemically inert and flexible substrate is introduced, which satisfies these requirements. We have developed a honeycomb-type retinal device that has a high-performance electrode for suprachoroidal transretinal stimulation. The device structure, in which conjunctional bioceramic substrates are embedded with large numbers of stimulating electrodes, provides high-resolution electrical stimulation. The custom CMOS microchip precisely controls the stimulation delivery of the electrodes to initiate artificial vision, offering a partial remedy for retinal ophthalmic diseases. The CMOS chip design was optimized to drastically reduce the number of input wirings. A high-performance stimulating electrode based on iridium oxide was fabricated using a unique solution process called chemical bath deposition (CBD). The honeycomb-type retinal device, equipped with CBD-derived iridium oxide electrodes, was used to evaluate the electrodes’ and device’s performances in vitro.

A simple and effective fabrication scheme involving sequential electrophoretic depositions of polystyrene (PS) microspheres (500nm and 1μm in diameter) and SiO2 sols (~5nm in diameter) to produce large-area ordered macroporous SiO2 inverse opals (2×2cm2) on ITO substrates is demonstrated. The zeta potentials for PS microsphere suspension and SiO2 sols are measured to determine an optimized processing window in which both samples carry negative surface charges and sol-gel transformation can be properly implemented. Our approach entails the electrophoresis of PS microspheres to render a colloidal crystal with negligible defects. Afterward, SiO2 sols are infiltrated to the interstitial voids among the closely-packed PS microspheres via another electrophoresis process, followed by an oxidation treatment to remove the PS colloidal template and complete the densification of SiO2 gels. The resulting SiO2 inverse opals reveal impressive surface uniformity and structural integrity. Fourier transform infrared spectroscopy confirms the complete removal of PS microspheres, leaving an intact SiO2 skeleton, whereas X-ray diffraction pattern indicates its amorphous nature. Keywords: Colloidal crystals, SiO2 inverse opals, Polystyrene microspheres, Electrophoresis, Sol-gel