Thin-film Metal Electrodes Research Articles

Molecularly Imprinted Polymer-Based Electrochemical Sensor for the Detection of Azoxystrobin in Aqueous Media.

This work presents an electrochemical sensor detecting a fungicide-azoxystrobin (AZO) in aqueous environments. This AZO sensor utilizes a thin-film metal electrode (TFME) combined with an AZO-selective molecularly imprinted polymer (AZO-MIP). The AZO-MIP was directly generated on TFME through electrochemical polymerization from the solution containing two functional monomers: aniline (Ani) and m-phenylenediamine (mPD), and the template: AZO, which was afterwards removed to form AZO-selective cavities in the polymer matrix. The AZO-MIP preparation was characterized by electrochemical and ellipsometry measurements. Optimization of the synthesis parameters, including the charge density applied during electrodeposition, the monomer-to-template ratio, was performed to enhance the sensor's performance. The results demonstrated that the AZO sensor achieved a low limit of detection (LOD) of 3.6 nM and a limit of quantification (LOQ) of 11.8 nM in tap water, indicating its sensitivity in a complex aqueous environment. The sensor also exhibited satisfactory selectivity for AZO in both ultrapure and tap-water samples and achieved a good recovery (94-119%) for the target analyte. This study highlights the potential of MIP-based electrochemical sensors for the rapid and accurate detection of fungicide contaminants in water, contributing to the advancement of analytical tools for water-quality monitoring and risk assessment.

Integration of multiple flexible electrodes for real-time detection of barrier formation with spatial resolution in a gut-on-chip system

In healthy individuals, the intestinal epithelium forms a tight barrier to prevent gut bacteria from reaching blood circulation. To study the effect of probiotics, dietary compounds and drugs on gut barrier formation and disruption, human gut epithelial and bacterial cells can be cocultured in an in vitro model called the human microbial crosstalk (HuMiX) gut-on-a-chip system. Here, we present the design, fabrication and integration of thin-film electrodes into the HuMiX platform to measure transepithelial electrical resistance (TEER) as a direct readout on barrier tightness in real-time. As various aspects of the HuMiX platform have already been set in their design, such as multiple compressible layers, uneven surfaces and nontransparent materials, a novel fabrication method was developed whereby thin-film metal electrodes were first deposited on flexible substrates and sequentially integrated with the HuMiX system via a transfer-tape approach. Moreover, to measure localized TEER along the cell culture chamber, we integrated multiple electrodes that were connected to an impedance analyzer via a multiplexer. We further developed a dynamic normalization method because the active measurement area depends on the measured TEER levels. The fabrication process and system setup can be applicable to other barrier-on-chip systems. As a proof-of-concept, we measured the barrier formation of a cancerous Caco-2 cell line in real-time, which was mapped at four spatially separated positions along the HuMiX culture area.

Free-Standing Carbon Nanotube Embroidered Graphene Film Electrode Array for Stable Neural Interfacing.

Implantable neural probes that are mechanically flexible yet robust are attractive candidates for achieving stable neural interfacing in the brain. Current flexible neural probes consist mainly of metal thin-film electrodes integrated on micrometer-thick polymer substrates, making it challenging to achieve electrode-tissue interfacing on the cellular scale. Here, we describe implantable neural probes that consist of robust carbon nanotube network embroidered graphene (CeG) films as free-standing recording microelectrodes. Our CeG film microelectrode arrays (CeG_MEAs) are ultraflexible yet mechanically robust, thus enabling cellular-scale electrode-tissue interfacing. Chronically implanted CeG_MEAs can stably track the activities of the same population of neurons over two months. Our results highlight the potential of ultraflexible and free-standing carbon nanofilms for stable neural interfacing in the brain.

Electrochemical sensor based on molecularly imprinted polymer for rapid quantitative detection of brain-derived neurotrophic factor

Neurodegenerative disorders necessitate early detection for timely diagnosis and treatment. Here, we present an electrochemical sensor comprising a robust biomimetic receptor, a molecularly imprinted polymer (MIP), integrated with a system of thin film metal electrodes for rapid detection of brain-derived neurotrophic factor (BDNF) as a potential neurodegenerative disorder biomarker. The MIP-based sensor utilizes the surface imprinting approach, where controlled polymer growth around the protein template creates geometrically-fit imprinted sites on the receptor surface. Following thorough characterization, the performance of the sensor was studied by differential pulse voltammetry. Under optimal conditions, the sensor exhibits an impressive limit of detection of 9 pg/mL for BDNF, showing over 5-fold selectivity against closely related neurotrophic factor proteins (CDNF and MANF) and 30-fold selectivity against proteins with similar pI values (e.g., CD48). Competitive binding assays further confirmed the sensor's selectivity, with BDNF inhibiting the binding of interfering proteins. Successful validation of BDNF detection in complex biological samples, specifically fetal bovine serum, highlighted the sensor's potential for real sample analysis. Compared to conventional biosensors, the presented strategy could unlock a new route to develop a highly desirable, robust sensing platform with strong affinity, specificity, and cost-effectiveness for diagnosing neurodegenerative disorders.

Amorphous metal thin film electrode for mechanically robust charge collection of organic photovoltaics

Amorphous metal thin film electrode for mechanically robust charge collection of organic photovoltaics

Microfluidic Electrochemical Glucose Biosensor with In Situ Enzyme Immobilization

The development and characterization of a microfluidic electrochemical glucose biosensor are presented herein. The transducer part is based on thin-film metal electrodes on a glass substrate. The biological recognition element of the biosensor is the pyrroloquinoline quinone-glucose dehydrogenase (PQQ-GdhB) enzyme, selectively in situ immobilized via microcontact printing of a mixed self-assembling monolayer (SAM) on a gold working electrode, while the microfluidic part of the device comprises microchannel and microfluidic connections formed in a polydimethylsiloxane (PDMS) elastomer. The electrode properties throughout all steps of biosensor construction and the biosensor response to glucose concentration and analyte flow rate were characterized by cyclic voltammetry and chronoamperometry. A measurement range of up to 10 mM in glucose concentration with a linear range up to 200 μM was determined. A detection limit of 30 µM in glucose concentration was obtained. Respective biosensor sensitivities of 0.79 nA/µM/mm2 and 0.61 nA/µM/mm2 were estimated with and without a flow at 20 µL/min. The developed approach of in situ enzyme immobilization can find a wide number of applications in the development of microfluidic biosensors, offering a path towards continuous and time-independent detection.

Thin Film Electrodes for Anodic Stripping Voltammetry: A Mini-Review.

Anodic stripping voltammetry (ASV) is a powerful electrochemical analytical technique that allows for the detection and quantification of a variety of metal ion species at very low concentrations in aqueous media. While early, traditional ASV measurements relied on macroscopic electrodes like Hg drop electrodes to provide surfaces suitable for plating/stripping, more recent work on the technique has replaced these electrodes with thin film metal electrodes generated in situ. Such electrodes are plated alongside the analyte species onto the surface of a primary electrode, producing a composite metal electrode from which the analyte(s) can then be stripped, identified, and quantified. In this minireview, we will explore the development and use of these unique electrodes in a variety of different applications. A number of metals (e.g., Hg, Bi, Sn, etc.) have shown promise as thin film ASV electrodes in both acidic and alkaline media, and frequently multiple metals in addition to the analyte of interest are deposited together to optimize the plating/stripping behavior, improving sensitivity. Due to the relatively simple nature of the measurement and its suitability for a wide range of pH, it has been used broadly: To measure toxic metals in the environment, characterize battery materials, and enable biological assays, among other applications. We will discuss these applications in greater detail, as well as provide perspective on future development and uses of these thin film electrodes in ASV measurements.

Metal-Molecule-Metal Junctions on Self-Assembled Monolayers Made with Selective Electroless Deposition.

Electronic transport through molecular-scale devices has been studied extensively for its extraordinary dimension superiority. Assembling such devices into large-scale functional circuits is crucial since the molecular tunnel junctions must be reliable, stable and reproducible during technological applications. In ideal circumstances, the device architecture should be designed such that the metal-molecule-metal (MMM) junctions can be analyzed by the more sensitive four point probe system. In this paper, we expound a delicate method to manufacture molecular junctions, which show excellent stability and reproducibility with high yields (>91 per cent). We form self-assembled monolayers (SAMs) on conductive Au thin film by microcontact printing and then generate robust covalently bound metal thin film electrodes on top of the SAMs by selective electroless deposition. Following MMM junction formation, a photoresist is coated and wells are opened on each feature by lithography. Then, Au thin film, as a permanent top electrode, is deposited into the photolithographically defined well. Conductivity analyzations were carried out on the 50 μm square junctions by the four point probe measurement, and the results showed reproducible tunneling I-V characteristics. This method reveals an approach not only offering a unique vehicle to investigate the electrical properties of molecule ensembles in MMMs, but also making a significant step toward MMM applications at the device level.

Size effect on stretchability of Cu films on wrinkled polydimethylsiloxane substrates

Stretchable electronics demand that the metal thin film electrodes have the capacity to experience large level of strains without obvious changes in electrical performance. This work investigated the effect of film thickness and wrinkle dimension on the stretchability of Cu films on polydimethylsiloxane substrates. It is revealed that the wrinkle dimension highly depends on the ultraviolet/ozone treatment time. The fracture strain increases until reaching a maximum and then decreases with increasing film thickness for smaller wrinkles. By contrast, the fracture strain monotonically increases as the film thickness increases for the larger wrinkles within the thickness range studied. Generally, the larger wrinkle dimension leads to a higher fracture strain for a given film thickness. The evolution of fracture strain can be rationalized in terms of the competition between the intrinsic stretchability of Cu films related to the grain size and the extrinsic strain concentration related to film thickness and wrinkle dimension.

Synergistic Effect of a Dual-Salt Liquid Electrolyte with a LiNO3 Functional Additive toward Stabilizing Thin-Film Li Metal Electrodes for Li Secondary Batteries.

Li metal thickness has been considered a key factor in determining the electrochemical performance of Li metal anodes. The use of thin Li metal anodes is a prerequisite for increasing the energy density of Li secondary batteries intended for emerging large-scale electrical applications, such as electric vehicles and energy storage systems. To utilize thin (20 μm thick) Li metal anodes in Li metal secondary batteries, we investigated the synergistic effect of a functional additive (Li nitrate, LiNO3) and a dual-salt electrolyte (DSE) system composed of Li bis(fluorosulfonyl)imide (LiTFSI) and Li bis(oxalate)borate (LiBOB). By controlling the amount of LiNO3 in DSE, we found that DSE containing 0.05 M LiNO3 (DSE-0.05 M LiNO3) significantly improved the electrochemical performance of Li metal anodes. DSE-0.05 M LiNO3 increased the cycling performance by 146.3% [under the conditions of a 1C rate (2.0 mA cm-2), DSE alone maintained 80% of the initial discharge capacity up to the 205th cycle, whereas DSE-0.05 M LiNO3 maintained 80% up to the 300th cycle] and increased the rate capability by 128.2% compared with DSE alone [the rate capability of DSE-0.05 M LiNO3 = 50.4 mAh g-1, and DSE = 39.3 mAh g-1 under 7C rate conditions (14.0 mA cm-2)]. After analyzing the Li metal surface using scanning electron microscopy and X-ray photoelectron spectroscopy, we were able to infer that the stabilized solid electrolyte interphase layer formed by the combination of LiNO3 and the dual salt resulted in a uniform Li deposition during repeated Li plating/stripping processes.

Bioinspired Ultrathin Piecewise Controllable Soft Robots

AbstractIn nature, animals or plants often use soft organs to move and hunt. Research works on bioinspired materials and devices have attracted more and more interest as which show the potential for future intelligent robots. As key components of soft robots, biomimetic soft actuators are adapted to greater requirements for convenient, accurate, and programmable controlling robots. Here, a class of materials and processing routes of ultrathin actuators are reported for bioinspired piecewise controllable soft robots, where the actuators associate with thermal‐responsible soft silicone thin film with thickness as thin as 45 µm and electrically driven by well mechanical designed metallic thin film electrodes. Multiple electrodes in the robots in charge of individual segments control allow the soft robots exhibiting similar functionalities of animals or plants (for example, imitating the tongue of a reptile, such as chameleon to hunt moving preys, and mimicking vines to tightly wind around objects). These bionic results in the soft robots demonstrate their advantages in precise and flexible operation, which provides a good reference for the future research of intelligent soft actuators and robots.

Strain-resilient electrical functionality in thin-film metal electrodes using two-dimensional interlayers.

Flexible electrodes that allow electrical conductance to be maintained during mechanical deformation are required for the development of wearable electronics. However, flexible electrodes based on metal thin-films on elastomeric substrates can suffer from complete and unexpected electrical disconnection after the onset of mechanical fracture across the metal. Here we show that the strain-resilient electrical performance of thin-film metal electrodes under multimodal deformation can be enhanced by using a two-dimensional (2D) interlayer. Insertion of atomically-thin interlayers — graphene, molybdenum disulfide, or hexagonal boron nitride — induce continuous in-plane crack deflection in thin-film metal electrodes. This leads to unique electrical characteristics (termed electrical ductility) in which electrical resistance gradually increases with strain, creating extended regions of stable resistance. Our 2D-interlayer electrodes can maintain a low electrical resistance beyond a strain in which conventional metal electrodes would completely disconnect. We use the approach to create a flexible electroluminescent light emitting device with an augmented strain-resilient electrical functionality and an early-damage diagnosis capability.

Enhanced stretchability of metal/interlayer/metal hybrid electrode.

Despite the excellent electrical conductivity of metal thin film electrodes, their poor mechanical stretchability makes it extremely difficult to apply them as stretchable interconnect electrodes. Thus, we propose a novel stretchable hybrid electrode (SHE) by adopting two strategies to overcome the metal thin film electrode limitations: grain size engineering and hybridization with conductive interlayers. The grain size engineering technique improves the inherent metal thin film stretchability according to the Hall-Petch theory, and the hybridization of the conductive interlayer materials, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) and carbon nanotube (CNT), suppresses crack propagation. Especially, the CNT-inserted SHE exhibits a decreased resistance change of approximately 32% in tensile test and 75% in a 10 000 cycle fatigue test because of the rough surface of the designed electrode, which relieves maximum stress by redistributing it more evenly to prevent penetrating crack propagation.

Ionic Liquid Modified Pt/C Electrocatalysts for the Oxygen Reduction Reaction in Polymer Electrolyte Fuel Cells

One of the main challenges of mass deployment of fuel cell electrical cars is the limited power density of the polymer electrolyte fuel cell (PEFC), requiring high loadings of precious Pt metal to drive the oxygen reduction reaction (ORR). Within the catalyst layer of PEFC electrodes, Pt nanoparticles are typically dispersed on porous Ketjenblack carbon due to its high surface area, and the ability of Pt to be deposited into the smaller mesopores of the carbon support; so that they can be protected from ionomer poisoning. Up to 62% of Pt nanoparticles can be buried in the interior of the mesopores1. As the cathode ORR takes place at the triple-phase boundary of the liquid electrolyte, oxygen gas, and solid Pt deposited on the carbon support, a sufficient diffusion of oxygen and protons in the liquid media is vital for the ORR reaction. However, Nafion as the proton conductor cannot penetrate into the micro and mesopores of the support due to the size exclusions; therefore, Pt nanoparticles buried within those pores will not be accessed by the reactants at dry conditions. Studies have shown that electric double layers formed at Pt-water interface can help mediate proton transport increasing proton conductivity by three orders of magnitude. Although, this conductivity is still about two orders of magnitude lower than that of Nafion2 , 3.The principle of electrocatalyst interface design in this work is to impregnate the high surface area (HSA) Ketjenblack carbon pores with a secondary phase, imidazolium-derived ionic liquids (ILs), that can fill the mesopores of the carbon support and provide satisfactory oxygen solubility and proton transfer due to high ΔpKa value and hydrogen-bonded network formation4 , 5. Pt/C-IL catalyst systems are prepared with 1-alkyl-3-metylimidazolium bis(trifluoromethylsulfonyl)imides with short cationic alkyl chain lengths including ([C2mim][NTf2]) and ([C4mim][NTf2]), along with 1-butyl-2,3-dimethylimidazolium bis(trifluoromethylsulfonyl)imide ([C4dmim][NTf2]) in order to study the effect of methyl group attachment to the carbon in the 2-position.The effect of the IL molecular structure on the electrochemical behavior of Pt/C catalyst is investigated in half-cell electrochemical set-up, rotating disk electrode (RDE). Figure 1a contains the cyclic voltammogram of pristine and IL-modified Pt/C samples. Pt/C catalyst exhibits electrochemical surface area (ECSA) loss after the IL modification. IL-modified Pt/C samples including Pt/C-[C2mim][NTf2], [C4mim][NTf2], and [C4dmim][NTf2] show ECSA values of 81.29, 78.1 and 78.9 m2 g-1 Pt’ respectively, which are lower than that of the pristine Pt/C. Moreover, IL molecules create a hydrophobic microenvironment that can lead to the repelling of the water molecules from Pt active sites protecting them from being oxidized; therefore, the onset potential of Pt-oxide formation is shifted to higher potentials and the coverage of the non-reactive oxygenated species is decreased, improving the specific activity of the electrocatalysts.Electrochemical impedance spectroscopy (EIS) is also implemented to measure overall effective proton diffusion resistance within the catalyst layers of Pt/C-IL-Nafion and Pt/C-Nafion. The linear portion of the Nyquist plot data at high frequencies shows a noticeably enhanced proton accessibility of the electrocatalyst in all Pt/C-Nafion-IL catalyst layers compared to that of Pt/C-Nafion (Figure 1b). References Huang, J., Li, Z. & Zhang, J. Review of characterization and modeling of polymer electrolyte fuel cell catalyst layer: The blessing and curse of ionomer. Front. Energy 11, 334–364 (2017). Zenyuk, I. V & Litster, S. Modeling ion conduction and electrochemical reactions in water films on thin-film metal electrodes with application to low temperature fuel cells. Electrochim. Acta 146, 194–206 (2014). Thompson, E. L. & Baker, D. Proton Conduction on Ionomer-Free Pt Surfaces. (2011). doi:10.1149/1.3635605 Miran, M. S. et al. Key factor governing the physicochemical properties and extent of proton transfer in protic ionic liquids: ΔpKa or chemical structure? Phys. Chem. Chem. Phys. 21, 418—426 (2018). Moschovi, A. M., Dracopoulos, V. & Nikolakis, V. Inter- and Intramolecular Interactions in Imidazolium Protic Ionic Liquids. J. Phys. Chem. B 118, 8673–8683 (2014). Figure 1

Electromechanical evaluation of sub-micron NiCr-carbon thin films as highly conductive and compliant electrodes for dielectric elastomers

This paper focuses on the electromechanical evaluation of combinations of novel sub-micron metal and carbon thin film electrodes for dielectric elastomers. The thin film electrodes are sputtered either onto 37.5 % biaxially pre-stretched polydimethylsiloxane (PDMS)-foils or on 57.5 % pre-stretched foils under pure shear conditions. The electrodes are wrinkled after relaxing the pre-stretch. The wrinkles in combination with the innovative sputtered sandwich-layers of nickel-chromium and carbon, with a total thin film thickness of 10 nm–40 nm, lead to exceptional electromechanical properties. With an initial resistance of only 500 Ω/square, some electrode configurations tolerate high strain up to 100 % without losing conductivity. 10 million cycles of mechanical load do not cause any major degradation of the thin films and their resistances. The capacitance-strain function is linear as long as the test strain is kept below the previously applied pre-stretch. During all the experiments, no delamination of these compliant thin film electrodes was observed. The force-displacement characteristics of the dielectric elastomer can be altered by applying high voltages on the electrodes, and thus, the actuator working principle is demonstrated. Depending on the kind of pre-stretch, some layer sequences are advantageous and others are disadvantageous when a low resistance at high strain is favored. In general, biaxially pre-stretched membranes with a metallic electrode configuration provide the best properties. Hence, this work proves, that sub-micron sandwich-layers of nickel-chromium and carbon are suitable for electrodes of dielectric elastomer actuators and sensors.

Heavily-Doped Bulk Silicon Sidewall Electrodes Embedded between Free-Hanging Microfluidic Channels by Modified Surface Channel Technology.

Surface Channel Technology is known as the fabrication platform to make free-hanging microchannels for various microfluidic sensors and actuators. In this technology, thin film metal electrodes, such as platinum or gold, are often used for electrical sensing and actuation purposes. As a result that they are located at the top surface of the microfluidic channels, only topside sensing and actuation is possible. Moreover, in microreactor applications, high temperature degradation of thin film metal layers limits their performance as robust microheaters. In this paper, we report on an innovative idea to make microfluidic devices with integrated silicon sidewall electrodes, and we demonstrate their use as microheaters. This is achieved by modifying the original Surface Channel Technology with optimized mask designs. The modified technology allows to embed heavily-doped bulk silicon electrodes in between the sidewalls of two adjacent free-hanging microfluidic channels. The bulk silicon electrodes have the same electrical properties as the extrinsic silicon substrate. Their cross-sectional geometry and overall dimensions can be designed by optimizing the mask design, hence the resulting resistance of each silicon electrode can be customized. Furthermore, each silicon electrode can be electrically insulated from the silicon substrate. They can be designed with large cross-sectional areas and allow for high power dissipation when used as microheater. A demonstrator device is presented which reached at a power of , limited by thermal conduction through the surrounding air. Other potential applications are sensors using the silicon sidewall electrodes as resistive or capacitive readout.

Electrode Effects on Flexible and Robust Polypropylene Ferroelectret Devices for Fully Integrated Energy Harvesters.

This work presents a characterization study of the electrode interface in polypropylene ferroelectret nanogenerators. An emphasis is made on the comparison of carbon nanotube fiber electrodes with traditional metallic thin film electrodes. Multiple experiments were performed on samples with the same electrode dimensions for a range of applied pressures. Results showed higher open-circuit voltage peak values for the thin film metal electrodes, regardless of the applied pressure. Interestingly, the difference in short-circuit current values between metal and carbon nanotube-based fiber electrodes was not as significant. The carbon nanotube fiber electrode was further investigated by post-treating the fiber with acetone and comparing the results with untreated carbon nanotube film electrodes and thin film metal electrodes. In an effort to enable a monolithic integration of ferroelectret energy harvesters with flexible energy storage elements, this work also presents studies on generation and leakage of induced free charge in the electrodes of flexible ferroelectret energy harvesters. It was found the current leakage through parasitic elements is a faster process than dipole relaxation in the polypropylene film. Finally, an electrode reliability study shows no significant difference in the electrical output of the devices with metallic thin film electrodes after single folding but shows a significant deterioration after crumpling; meanwhile, these processes had no effect on the performance of similar devices with carbon nanotube fiber-based electrodes.

Electrocatalytic Behavior of Hydrogenated Pd-Metallic Glass Nanofilms: Butler-Volmer, Tafel, and Impedance Analyses

Electrocatalytic activity and sorption behavior of hydrogen in nanosized Pd–Si–(Cu) metallic glass thin film and Pd thin film electrodes sputtered on a Si/SiO2 substrate were investigated by linear sweep voltammetry, cyclic voltammetry, and electrochemical impedance spectroscopy. The electrode MG4 (Pd69Si18Cu13) exhibits the best performance with the highest electrocatalytic activity in the hydrogen evolution region with less than half of the Tafel slope of Pd thin film of the same thickness and lowest overpotential at 10 mA cm−2. A new approach has been adopted by a nonlinear fitting of the entire region of the polarization curve (far- and near-equilibrium cathodic and anodic regions) to the Butler-Volmer model. α parameter is lowest for the MG2 electrode (Pd79Si16Cu5), marking that nonequilibrium conditions change the reaction kinetics. Together with MG2, MG4 shows the lowest Bode magnitude values for hydrogen sorption and evolution regions, indicating that the bonding and release of hydrogen atoms to the electrode is easier. MG4 electrode shows a dramatic decrease of the overpotential after 100 cycles, yielding an increase in hydrogen activity. Besides, MG4 exhibits the sharpest current density drop in the HER region in cyclic voltammetry compared with other MG and Pd electrodes, indicating higher electrocatalytic activity towards hydrogen evolution. The findings highlight the influence of the selected metallic glasses for the design and development of metal catalysts with higher sorption kinetics and/or electrocatalytic turnover.

Optimized plasma-assisted bi-layer photoresist fabrication protocol for high resolution microfabrication of thin-film metal electrodes on porous polymer membranes

Structured metal thin-film electrodes are heavily used in electrochemical assays to detect a range of analytes including toxins, biomarkers, biological contaminants and cell cultures using amperometric, voltammetric and impedance-based (bio)sensing strategies as well as separation techniques such as dielectrophoresis. Over the last decade, thin-film electrodes have been fabricated onto various durable and flexible substrates including glass, silicon and polymers. However, the combination of thin-film technology with porous polymeric substrates frequently used for biochips often results in limited resolution and poor adhesion of the metal thin-film, thus severely restricting reproducible fabrication and reliable application in e.g. organ-on-a-chip systems. To overcome common problems associated with micro-structured electrode manufacturing on porous substrates, we have optimized a bi-layer lift-off method for the fabrication of thin-film electrodes on commercial porous polyester membranes using a combination of LOR3A with AZ5214E photoresists. To demonstrate practical application of our porous electrode membranes for trans-epithelial electrical resistance measurements a tetrapolar biosensing set-up was used to eliminate the artificial resistance of the porous polymer membrane from the electrochemical recordings. Furthermore, barrier resistance of Bewo trophoblast epithelial cells was compared to a standard Transwell assay readout using a EVOM2 volt-ohm meter.•Bi-layer photo resist lift-off yields resolution down to 2.5 μm.•Argon Plasma-assisted lift-off results in improved adhesion of gold thin films and eliminates the need for chromium adhesion layers.•Membrane electrodes can be used for elimination of the porous membrane resistance during tetra-polar epithelial resistance measurements.

Quadruple H-Bonding Cross-Linked Supramolecular Polymeric Materials as Substrates for Stretchable, Antitearing, and Self-Healable Thin Film Electrodes.

Herein, we report a de novo chemical design of supramolecular polymer materials (SPMs-1-3) by condensation polymerization, consisting of (i) soft polymeric chains (polytetramethylene glycol and tetraethylene glycol) and (ii) strong and reversible quadruple H-bonding cross-linkers (from 0 to 30 mol %). The former contributes to the formation of the soft domain of the SPMs, and the latter furnishes the SPMs with desirable mechanical properties, thereby producing soft, stretchable, yet tough elastomers. The resulting SPM-2 was observed to be highly stretchable (up to 17 000% strain), tough (fracture energy ∼30 000 J/m2), and self-healing, which are highly desirable properties and are superior to previously reported elastomers and tough hydrogels. Furthermore, a gold, thin film electrode deposited on this SPM substrate retains its conductivity and combines high stretchability (∼400%), fracture/notch insensitivity, self-healing, and good interfacial adhesion with the gold film. Again, these properties are all highly complementary to commonly used polydimethylsiloxane-based thin film metal electrodes. Last, we proceed to demonstrate the practical utility of our fabricated electrode via both in vivo and in vitro measurements of electromyography signals. This fundamental understanding obtained from the investigation of these SPMs will facilitate the progress of intelligent soft materials and flexible electronics.