Microstructured Electrodes Research Articles

Fabrication and Characterization of PEDOT:PSS‐Based Microstructured Electrodes for In Vitro Cell Culture

Abstract Bioelectronics is an evolving field focused on creating efficient interfaces between electronic systems and biological environments, where electrodes are crucial for detecting, recording, and stimulating signals. While traditional fabrication techniques offer high precision, they are costly and lack scalability. Vacuum soft lithography offers a scalable, time‐efficient alternative for manufacturing microstructured electrodes. When combined with poly(3,4‐ethylenedioxythiophene) poly(styrene sulfonate) (PEDOT:PSS), a conducting polymer known for its biocompatibility and stability, this approach presents a promising solution for advancing bioelectronic applications. This study demonstrates the successful application of vacuum soft lithography for fabricating PEDOT:PSS‐based microstructured electrodes. These PEDOT:PSS‐based microstructured electrodes are fabricated and characterized based on their morphology, mechanics, and electrochemical properties. The PEDOT:PSS mixture containing 2% (3‐glycidyloxypropyl)trimethoxysilane (GOPS) demonstrates optimal properties, achieving an excellent balance of reproducibility, conductivity, and mechanical integrity, with in vitro cytocompatibility confirmed through testing with the MDA‐MB‐231 breast cancer cell line. This approach offers significant advantages, including reduced costs and production times, making it a viable alternative to conventional methods. Future research will explore its use with other conducting materials for broader bioelectronic applications.

Speckle noise reduction in laser projection using a liquid crystal device with stacked microstructured electrodes.

Laser speckle is a major challenge for laser projectors, and its reduction is crucial for improving laser display technologies. This study introduces a tunable multifocal liquid crystal microlens array (TMLCMA) with a triple-electrode structure and vertically aligned liquid crystals exhibiting negative dielectric anisotropy, designed to mitigate speckle noise. The TMLCMA operates in three modes: monofocal concave, multifocal concave, and multifocal convex, depending on the voltage driving scheme used. In monofocal modes, the speckle contrast decreases from 0.46 to 0.35; in multifocal modes, it is further reduced from 0.46 to 0.15. These multifocal properties effectively disrupt laser coherence, leading to a greater reduction in speckle noise compared to a conventional monofocal microlens array. Our results demonstrate that integrating the TMLCMA into the laser projection system significantly enhances image quality, underscoring its potential for improving laser display performance.

Flexible sandwich-shaped piezoresistive sensors with microtextured electrodes and porous sensing layers of carbon nanocomposite

Flexible piezoresistive sensors based on carbon nanomaterials have attracted significant attention with regard to their application to wearable electronics. The enhanced performance of these sensors is primarily due to the integration of microstructures and conductive coatings. In this study, a flexible sandwich-shaped piezoresistive pressure sensor is fabricated by adopting microstructured electrodes and a porous sensing layer of carbon nanocomposite. The microtextured electrodes are obtained from a template by three-dimensional printing using digital light processing (DLP), and the porous structure is obtained by scarification of an NaCl crystal template. Multiwalled carbon nanotubes (MWCNTs) and graphene nanoparticles (GNPs), composited with polydimethylsiloxane and silica (ESSIL 296), are used to fabricate the functional structures, including the upper and lower electrode layers and a sandwiched porous sensing layer. The sensor exhibits a rapid response and recovery speed (∼80 ms), a high sensitivity (0.437 kPa−1) within a range of 0–1.08 kPa, and excellent stability. In addition, such sensors demonstrate potential applications for finger motion monitoring and information encryption.

Electrohydrodynamic jet printing of micro-structured electrode featuring 3D gold micropillar array for non-enzymatic detection of glucose

Electrohydrodynamic jet printing of micro-structured electrode featuring 3D gold micropillar array for non-enzymatic detection of glucose

Dry Coating with Hydrophilic and Hydrophobized Nanostructured Fumed Alumina (Al2O3) on SiOx/C Anodes for Enhanced Lithium-Ion Battery Performance.

Silicon-based anode materials hold great promise for advancing lithium-ion battery technology due to their high specific capacity, low voltage platform, abundant resources, and environmental benefits. However, their inherent challenges, such as poor electrical conductivity, significant volume expansion, and instability of the solid-electrolyte interphase layer, hinder their widespread commercialization. This study addresses these issues using the dry particle coating method with nanostructured fumed aluminum oxide (Al2O3), a novel approach with significant potential for commercial scalability. The impact of surface wettability on performance is studied by applying metal oxide coatings, using hydrophilic and hydrophobized surfaces. Electrochemical evaluation shows a significant increase in rate performance and cycle life when the surface coating is applied, with improvements in discharge capacity of around 10% and 17% for hydrophobized and hydrophilic Al2O3 coatings, respectively, after 100 cycles. The Al2O3 coating protects the surface of the active material, preventing particle pulverization, reducing side reactions, and decreasing electrolyte decomposition and hydrofluoric acid content. While overall performance improves with coating, the best results are achieved with the hydrophilic coating, which fosters a more homogeneous microstructured electrode. These findings underscore the potential of the dry particle coating technique with Al2O3 to enhance Si-based anode performance and facilitate commercial application.

Motion artifact–controlled micro–brain sensors between hair follicles for persistent augmented reality brain–computer interfaces

Modern brain-computer interfaces (BCI), utilizing electroencephalograms for bidirectional human-machine communication, face significant limitations from movement-vulnerable rigid sensors, inconsistent skin-electrode impedance, and bulky electronics, diminishing the system's continuous use and portability. Here, we introduce motion artifact-controlled micro-brain sensors between hair strands, enabling ultralow impedance density on skin contact for long-term usable, persistent BCI with augmented reality (AR). An array of low-profile microstructured electrodes with a highly conductive polymer is seamlessly inserted into the space between hair follicles, offering high-fidelity neural signal capture for up to 12 h while maintaining the lowest contact impedance density (0.03 kΩ·cm-2) among reported articles. Implemented wireless BCI, detecting steady-state visually evoked potentials, offers 96.4% accuracy in signal classification with a train-free algorithm even during the subject's excessive motions, including standing, walking, and running. A demonstration captures this system's capability, showing AR-based video calling with hands-free controls using brain signals, transforming digital communication. Collectively, this research highlights the pivotal role of integrated sensors and flexible electronics technology in advancing BCI's applications for interactive digital environments.

Artificially Weaved Textile‐like Surface Micromachined Graphene‐Polymer Flexible Bioelectrodes

Abstract Dry, flexible, and self‐adhesive sensors are critical enablers for wearable, long‐term biosignal recording devices. Here, an ultra‐thin, flexible textile‐like microstructured electrode with self‐adhesive abilities is presented for conformal attachment and long‐term electrocardiography (ECG) recording. The reported electrode is manufactured using a spin‐coatable and electron‐beam sensitive formulation of poly (methyl methacrylate) (PMMA) resist, also commonly known as acrylic, which is at the same time a widely‐employed material in the textile industry. The textile‐like structure of the bioelectrodes with a linewidth of 100 µm and gap size of 100 µm is achieved by patterning PMMA through oxygen plasma and a hard mask layer without requiring complex and expensive e‐beam lithography (EBL) processes. Graphene oxide (GO) is introduced to the electrodes as active material followed by a reduction step using eco‐friendly pure vitamin C (L‐ascorbic acid). The functionality of the reported electrodes is benchmarked against pre‐gelled wet Ag/AgCl electrodes, comparing their signal quality and skin‐electrode impedance, and achieving a correlation score of 98.84%. Furthermore, it is demonstrated that the electrodes are flexible, water resistant, and can be used multiple times; rendering them suitable for wearable electronics purposes even during intense physical activities both in dry and wet environments.

Flower-like Cu2ZnSnS4 (CZTS) transition metal sulphide (TMS) as a micro-structured electrode in rechargeable lithium batteries

Flower-like Cu2ZnSnS4 (CZTS) transition metal sulphide (TMS) as a micro-structured electrode in rechargeable lithium batteries

(Invited) Application of Structured Electrodes for Photoelectrochemisry Under Dark

We employed well-defined nano- and micro-structured electrodes for water electrolysis. Based on the observation of bubble generation induced by hydrogen and oxygen evolution reactions, the catalytic activity of the structured electrodes was characterized, suggesting the contribution of molecule polaritons to enhancing water reduction and oxidation, respectively. The potential application of this approach is discussed for photoelectrochemistry under dark conditions.

The Effect of Organic Additive on Electrochemical Fabrication of Micro-Structured Electrode for Reverse Electrodialysis

Reverse electrodialysis (RED) is a type of salinity gradient power generation technology that is a renewable energy source that converts chemical energy into electrical energy. RED uses seawater and salt differences to produce electrical energy. Intensive research is needed to develop electrodes with excellent conductivity to reduce electrode resistance and increase performance when operating reverse electrodialysis. Conventionally, the state of the art electrode is prepared by electrodepositing Pt on metal substrate, such as Ti mesh (Pt/Ti mesh) in acidic medium. However, due to the dimension of porous mesh structure, it is difficult to form an uniform Pt layer with high coverage via normal potential- or current-controlled electrodeposition. In response to this, this research proposes an additive-induced electrodeposition for the preparation of Pt/Ti mesh electrode. A trisodium citrate (TSC) is chosen to be an additive. TSC plays both as a leveler and a suppressor and therefore it helps to control the kinetics of electrochemical process. The effect of TSC and its content on the physicochemical and electrochemical property of Pt/Ti electrode is addressed. The RED single cell test is conducted with the electrodes manufactured according to the TSC content, and the performance is compared and analyzed accordingly.

Impactof Surface Microstructure and Properties ofAluminum Electrodes on the Plating/Stripping Behavior of Aluminum-BasedBatteries Using Imidazolium-Based Electrolyte

The 99.99% Al usedfor negative Al electrodes in aluminum-basedbattery studies is expensive. This is primarily due to the complexchallenges associated with fabricating 99.99% Al, particularly theremoval of Fe impurities from Al melts. Despite the importance ofthis issue for the future commercialization of Al-based batteries,it has been largely overlooked. This work accordingly studied theplating/stripping behavior of Al containing 1 wt % iron (Al 1% Fe)as an alternative electrode using conventional ([EMIm]Cl and AlCl3) electrolyte. Simultaneously, the impact of the surface microstructureof Al 1% Fe on the plating/stripping behavior was examined. The resultsindicate that the difference in the plating/stripping cycling of Al1% Fe alloys and 99.99% Al is negligible. Thus, Al 1% Fe negativeelectrodes could serve as an efficient and commercially viable alternativeto 99.99% Al for plating/stripping in Al-based batteries. This isan essential finding because facile and commercial fabrication ofAl 1% Fe electrodes is absolutely feasible. The results are furtherdiscussed in terms of the impact of the Al surface microstructure(i.e., grain size, defect density, grain boundary distribution, crystalorientation, and intermetallic phases) on plating/stripping behavior.Moreover, this study provides insights into how the interphase layerformed on Al electrodes influences plating/stripping behavior.

Microstructured Self-Healing Flexible Tactile Sensors Inspired by Bamboo Leaves.

Wearable electronic devices with multifunctions such as flexible, integrated, and self-powered play a crucial role in the fields of health monitoring, motion monitoring, and human-computer interaction. However, their core basic components, flexible pressure sensors, face challenges including poor long-term stability and insufficient real-time sensing accuracy. In order to solve the challenges of long-term, stable, and accurate sensing of the sensor, this paper prepares polydimethylsiloxane (SHPDMS) with intrinsic self-healing property and designs a high-sensitivity self-healing capacitive flexible pressure sensor with dual microstructures (grating microstructured electrodes and microporous dielectric layer) as the substrate based on SHPDMS. Specifically speaking, the self-healing of the sensor under mild conditions was realized by introducing reversible imine bonds with low bonding energy into the polydimethylsiloxane (PDMS) flexible substrate, which solved the problem of the material's long-term service durability. A grating-like microstructure was introduced into the flexible electrode by using a spotted bamboo taro leaf as a template, and a dual microstructure sensor was constructed by combining it with a microporous dielectric layer doped with single-walled carbon nanotubes. This way reduces the elastic modulus of the dielectric layer, improves the dielectric constant of the sensor under loading, and thus significantly improves the sensor's sensitivity and extends the measurement accuracy in a low-stress range. The prepared self-healing flexible sensor achieves a sensitivity of 3.6 kPa-1, a minimum detection limit of 5 Pa, a response recovery time of less than 80 ms, and stability over 5000 cycles, which exceeds most previously reported silicone rubber-based capacitive flexible sensors.

Nonequilibrium fast-lithiation of Li4Ti5O12 thin film anode for LIBs

Li4Ti5O12 (LTO) is known for its zero-strain characteristic in electrochemical applications, making it a suitable material for fast-charging applications. Here, we systematically studied the quasi-equilibrium and non-equilibrium lithium-ion transportation kinetics in LTO thin-film electrodes, across a range of scales from the crystal lattice to the microstructured electrodes. At the crystal lattice scale, during the non-equilibrium lithiation process, lithium ions are dispersedly embedded into the 16c position, resulting in more 8a → 16c migration compared with the quasi-equilibrium lithiation, and forming numerous fast lithium diffusion channels inside the LTO lattice. At the microstructural electrode scale, optical spectrum characterizations supported the “nano-filaments” lithiation model in polycrystalline LTO thin-film electrodes during the lithiation process. Our results reveal the patterns of lithium migration and distribution within the LTO thin film electrode under the non-equilibrium and quasi-equilibrium lithiation process, offering profound insights into the potential optimization strategies for enhancing the performance of fast-charging thin film batteries.

Continuous-Flow Electrochemical Microreactor with Three-Dimensional Micro-Structured Electrodes Promoting Bioalcohol Upgrading Coupled with Hydrogen Production

Continuous-Flow Electrochemical Microreactor with Three-Dimensional Micro-Structured Electrodes Promoting Bioalcohol Upgrading Coupled with Hydrogen Production

Integrated surface microstructure and enhanced dielectric constant for constructing simple, low-cost, and high-performance flexible capacitive pressure sensor

Integrated surface microstructure and enhanced dielectric constant for constructing simple, low-cost, and high-performance flexible capacitive pressure sensor

Benchtop Fabricated Nano-Roughened Microstructured Electrodes for Electrochemical and Surface-Enhanced Raman Scattering Sensing.

Tailoring a material's surface with hierarchical structures from the micro- to the nanoscale is key for fabricating highly sensitive detection platforms. To achieve this, the fabrication method should be simple, inexpensive, and yield materials with a high density of surface features. Here, using benchtop fabrication techniques, gold surfaces with hierarchically structured roughness are generated for sensing applications. Hierarchical gold electrodes are prepared on pre-stressed polystyrene substrates via electroless deposition and amperometric pulsing. Electrodes fabricated using 1mm H[AuCl₄] and roughened with 80 pulses revealed the highest electroactive surface area. These electrodes are used for enzyme-free detection of glucose in the presence of bovine serum albumin and achieved a limit of detection of 0.36mm, below glucose concentrations in human blood. The surfaces nanoroughened with 100 pulses also showed excellent surface-enhanced Raman scattering (SERS) response for the detection of rhodamine 6G, with an enhancement factor of ≈2×106 compared to detection in solution, and for the detection of a self-assembled monolayer of thiophenol, with an enhancement factor of ≈30 compared to the response from microstructured gold surfaces. It is envisioned that the simplicity and low fabrication cost of these gold-roughened structures will expedite the development of electrochemical and SERS sensing devices.

Bioelectrochemical Sensing Using Benchtop Fabricated Nanoroughened Microstructured Electrodes

Abstract Cost‐effective miniaturized electrodes that maintain a high electroactive surface area (ESA) are needed for the widespread deployment of point‐of‐care sensors. Cost‐effective methods are recently developed to fabricate nanoroughened microstructured gold electrodes (NR‐MSEs) with ultrahigh ESA. In this work, the effectiveness of NR‐MSEs for bioelectrochemical enzymatic sensors is evaluated. A glucose sensor is constructed by first casting onto NR‐MSEs a solution containing reduced graphene oxide decorated with gold nanoparticles, glucose oxidase, and glutaraldehyde, followed by a solution containing ferrocene, and a layer of chitosan to prevent the leakage of sensor components. A urea biosensor is also fabricated using Nafion as a cationic exchanger for the electropolymerization of polyaniline, followed by the deposition of a composite containing urease, bovine serum albumin, and glutaraldehyde. The limit of quantification for both biosensors is below clinically relevant concentrations of the analytes in biofluids, 0.67 mm for glucose and 1.70 mm for urea. The sensors exhibit excellent performance in complex matrixes (human blood serum and wine for glucose and human blood serum and urine for urea), with recovery for spiked analytes in the range of 92–108%. It is anticipated that NR‐MSEs will expedite the development of highly sensitive bioelectrochemical sensors for use in resource‐limited settings.

<i>Hofmeister</i> effect regulated gel iontronic sensors for wide-range pressure perception

<p>Flexible pressure sensors, vital for medical, human-machine interaction, and intelligent recognition applications due to their high-sensitivity, excellent-linearity, and broad-pressure response, face challenges in achieving a harmonious balance among these attributes. Inspired by the gradient modulus in human skin layers, we proposed a pioneering method to adjust the gradient elastic modulus of amino trimethylene phosphonic acid (ATMP)-assisted polyvinyl alcohol (PVA) hydrogel through the <i>Hofmeister</i> effect, introducing micro-pyramid electrodes. This innovative approach successfully constructs a bio-gradient gel iontronic sensor (BGGITS) with an ultra-wide-range perception. The BGGITS exhibits a linear high-sensitivity of 700 kPa<sup>-1</sup> within a broad-pressure detection range of up to 800 kPa. The composite design, integrating gradient gel and microstructure electrodes, demonstrates exceptional pressure resolution and mechanical stability. This biomimetic skin pressure sensor holds promise for achieving linear high-sensitivity across a broader pressure range simultaneously and may find applications in electronic skin for health monitoring and tactile perception in the future.</p>

Fabrication and application of flexible EEG dry electrode based on stacked-template method

A barb micro-structured (BMS) dry electrode is presented. The coating properties, electrical and electrochemical properties are studied. BMS electrodes have better resistance to hair interference, and to sweat corrosion after thiol treatment.

Platinum-sputtered microstructured electrodes for enhanced PEM electrolysis

Platinum-sputtered microstructured electrodes for enhanced PEM electrolysis