Interdigitated Electrodes Research Articles

Hydrophobically Associated Hydrogel for High Sensitivity and Resolution of an Interdigital Electrode Pressure Sensor.

Hydrogel-based flexible strain sensors have been known for their excellent ability to convert different motions of humans into electrical signals, thus enabling real-time monitoring of various human health parameters. In this work, a composite hydrogel with hydrophobic association and hybrid cross-linking was fabricated by using polyacrylamide (PAm), surfactant sodium dodecyl sulfate (SDS), lauryl methacrylate (LMA), and polypyrrole (PPy). The dynamic dissociation-conjugation among LMA, SDS, and PPy could dissipate energy to improve the toughness of hydrogels. The SDS/PPy/LMPAm composite hydrogel with a toughness of 1.44 MJ/m3, tensile fracture stress of 345 kPa, tensile strain of 1021%, and electrical conductivity of 0.57 S/m was obtained. Furthermore, an interdigital electrode flexible pressure sensor was designed to replace the bipolar electrode flexible pressure sensor, which greatly improved the sensitivity and resolution of the pressure sensor. The SDS/PPy/LMPAm composite hydrogel-based interdigital electrode flexible pressure sensor showed extraordinary stability and identified different hand gestures as well as monitored the pulse signal of humans. Moreover, the characteristic systolic and diastolic peaks were clearly observed. The pulse frequency (65 times/min) and the radial artery augmentation index (0.57) were calculated, which are very important in evaluating the arterial vessel wall and function of human arteries.

Facile and Cost-Effective Fabrication of Highly Sensitive, Fast-Response Flexible Humidity Sensors Enabled by Laser-Induced Graphene.

The need to simplify fabrication processes and reduce costs for high-performance humidity sensors is increasingly vital, especially in fields such as healthcare and agriculture. This study introduces a simple and cost-effective approach using laser-induced graphene (LIG) on a polyimide film to create highly sensitive and fast-response flexible humidity sensors. The LIG acts as the electrode, while the porous polyimide between the interdigital LIG electrodes serves as the humidity sensing material, showing changes in electrical conductivity based on the humidity levels. The LIG humidity sensor, an ionic-conduction type, exhibits remarkable sensitivity, with a 28,231-fold increase in current as relative humidity changes from 26.1 to 90.2%. It also boasts of ultrashort response/recovery times (less than 0.5/7 s), providing significant advantages in detecting rapid and subtle humidity variations compared to a commercially available MEMS humidity sensor. We successfully demonstrated the LIG humidity sensor's capabilities in ultrafast breathing monitoring (≈174 times per minute), moisture detection of grains, and detection of sudden water pipe leakage. Due to its straightforward and cost-effective fabrication process, the LIG humidity sensor holds immense practical value for affordable, widespread use across various applications.

Nondestructive dielectric measurement method for orientation distribution of liquid crystal polymers film

Liquid crystal polymers (LCP) are widely used materials in 5G applications. The LCP films easily tend to form an uneven orientation distribution that degrades their service properties. However, tailoring its orientation distribution remains a challenge, primarily because traditional measurement methods are unable to non-destructively measure the orientation distribution of large-area LCP films attributed to penetration depth constraints or sample preparation requirements. Capitalizing on its inherent orientation-induced dielectric anisotropy, we propose a nondestructive dielectric measurement method for the orientation distribution of LCP film using an interdigital electrodes array. Compared to polarized FTIR and WAXS/SAXS, the dielectric method provides a universally applicable solution, even in intricate scenarios like regions with wrinkles in LCP films, films with substantial thickness, and those lacking large-scale structures. Moreover, the accurate measurement of orientation distribution confirms that the large surface roughness and significant variations in thickness distribution are attributed to the uneven orientation distribution. The findings provide a “visual window” for precisely tailoring the orientation structure of LCP films for 5G applications and beyond.

Semiconductive (Cu–S)n Metal–Organic Frameworks Hybrid Polyaniline Nanocomposites as Hydrogen Sulfide Gas Sensor

A semiconductive (Cu–S)n metal–organic framework (MOF) incorporated polyaniline (PANI) nanocomposite was applied for hydrogen sulfide (H2S) gas sensing. The (Cu–S)n MOF nanosheets were successfully synthesized using a one-pot reflux method. First, fiber-like (Cu–S)n MOF/ PANI nanocomposites were prepared through an in situ oxidative polymerization. As evaluated by field-emission transmission electron microscopy (FE-TEM), the nanosized spherical (Cu–S)n MOF particles were well-distributed in the fiber matrix. Then, the nanocomposite was spin-coated onto an interdigitated electrode (IDE) for H2S gas sensing, displaying high sensitivity, selectivity, repeatability, and stability similar to pure PANI. As a result, 3wt% (Cu–S)n MOF/ PANI nanocomposite showed the best performance for H2S detection. The mechanism for improving H2S sensing performance might be attributed to the conductive composite networks' significantly enhanced conductivity and increased doping sites of the (Cu–S)n MOF. In addition, the energy band gaps of PANI-based nanocomposites were optimized by the incorporated (Cu–S)n MOF, indicating the successful hybridization of energy levels between inorganic MOF and organic PANI. This study first demonstrates semiconductive MOF-PANI-based nanocomposites for H2S gas sensing.

Characteristic of graphene-based thick film gas sensor for ethanol and acetone vapor detection at room temperature

<p>Ethanol and acetone are volatile organic compound gases widely used in food processing. Health problems such as irritation of the eyes, nose, and throat can affect human health if exposed to these gases. Two graphene gas sensors were fabricated using a screen-printing technique onto a glass substrate to compare their performance to the acetone and ethanol vapors at room temperature. The graphene paste was prepared by mixing 95 wt.% of the binder with 5 wt.% of graphene nanoflakes. A silver paste was used asthe interdigitated electrode of the gas sensor and becamethe first layer of the gas sensor. The silver paste was deposited on the glass substrate using a screen-printing technique and fired at 150°C for 15 minutes. Next, the graphene paste was depositedonto the interdigitated electrode using a screen-printing technique and becamethe second layer of the gas sensor. The graphene was annealed at 200°C for 30 minutes. Both graphene gas sensors responded well to ethanol and acetone vapor with an n-typed gas sensor at room temperature. As a comparison, the graphene gas sensor showed better characteristics in terms of response and recovery characteristicsto ethanol vapor than acetone vapor at room temperature. The response and response time of the graphene-based thick film gas sensor to ethanol were approximately 21.89 and 24.08, respectively.</p>

Fine-Feature Additively Dry Printed Passive Wireless Sensor Tag

Wireless passive sensors have many applications, from precision agriculture to structural health monitoring. A simple but useful wireless passive sensor tag consists of a planar inductor coupled with a planar interdigitated electrode capacitor, forming an inductor-capacitor (LC) loop. Either the planar inductor or the planar interdigitated electrode capacitor can be used as the sensor. For example, the inductor could be used for proximity detection with an external ferrous object, or the capacitor could be used to measure the relative humidity of the surrounding air. The planar inductor, however, is also used to inductively couple the sensor tag to a base station feedback oscillator. As a result, the LC loop on the sensor tag tunes the base station oscillator’s output frequency accordingly. In this work, the planar inductor and the planar interdigitated electrode capacitor were printed on a polyimide substrate using a novel laser-based additive nanomanufacturing (ANM) and dry printing technology. With this fabrication process, approximately 2 micron thick silver traces were printed to realize a 34 loop planar inductor and a 69 tooth interdigitated electrode capacitor, with a nominal trace and space width of 6 mils (152.4 microns). This recently developed laser-based ANM technique allows for much finer trace and space widths, as well as a much larger variety of electronic materials, to be printed, compared to more traditional ink-based printed electronics manufacturing techniques.

Needle flower-like ZnO-based chemiresistive sensor for efficient detection of formaldehyde vapors

The development of a chemiresistive sensor that uses needle-flower-like ZnO to effectively detect formaldehyde vapors is highlighted in the paper. The hydrothermal process at low temperature was used to prepare the sensing material. The morphological and structural characteristics of the synthesized material were assessed using X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Using a micropipette, the sensing material was transferred to the surface of the gold-based interdigitated electrodes to fabricate the device. The fabricated sensor was found to be more selective and sensitive to formaldehyde in the sensing study. The results showed an approximate response of 8 at 250 °C and 75 ppm formaldehyde. The lowest detection limit of the sensor was calculated as 480 ppb. The sensor has a great potential to monitor formaldehyde vapors in the indoor environment.

Surface and Conductivity Characterization of Layered Organic Ionic Plastic Crystal (OIPC)-Polymer Films.

Organic ionic plastic crystals (OIPCs) are attractive solid electrolyte materials for advanced energy storage systems owing to their inherent advantages (e.g., high plasticity, thermal stability, and moderate ionic conductivity), which can be further improved/deteriorated by the addition of polymer or metal oxide nanoparticles. The role of the nanoparticle/OIPC combinations on the resultant interphase structure and transport properties, however, is still unclear due to the complexity within the composite structures. Herein, we demonstrate a systematic approach to specifically interrogating the interphase region by fabricating layered OIPC/polymer thin films via spin coating and correlating variation in the ionic conductivity of the OIPC with their microscopic structures. In-plane interdigitated electrodes have been employed to obtain electrochemical impedance spectroscopy (EIS) spectra on both OIPC and layered OIPC/polymer thin films. The thin-film EIS measurements were evaluated with conventional bulk EIS measurements on the OIPC pressed pellets and compared with EIS obtained from the OIPC-polymer composites. Interactions between the OIPC and polymer films as well as the morphology of the film surfaces have been characterized through multiple microscopic analysis tools, including scanning electron microscopy, energy-dispersive X-ray spectroscopy, atomic force microscopy, and optical profilometry. The combination of EIS analysis with the microscopic visualization of these unique layered OIPC/polymer thin films has confirmed the impact of the OIPC-polymer interphase region on the overall ionic conductivity of bulk OIPC-polymer composites. By changing the chemistry of the polymer substrate (i.e., PMMA, PVDF, and PVDF-HFP), the importance of compatibility between the components in the interphase region is clearly observed. The methods developed here can be used to screen and further understand the interactions among composite components for enhanced compatibility and conductivity.

Non-enzymatic glucose detection with screen-printed chemiresistive sensor using green synthesised silver nanoparticle and multi-walled carbon nanotubes-zinc oxide nanofibers

Non-enzymatic screen-printed chemiresistive interdigitated electrodes (SPCIE) were designed and fabricated using a low-cost screen-printing method for detection of the glucose. The interdigitated electrodes (IDE) pattern was printed using conductive graphene ink on the glossy surface of the photo paper. The proposed glossy photo paper-based SPCIE are functionalized with multi-walled carbon nanotubes-zinc oxide (MWCNTs-ZnO) nanofibers to create the chemiresistive matrix. Further, to bind these nanofibers with the graphene electrode surface, we have used the green synthesized silver nanoparticles (AgNPs) with banana flower stem fluid (BFSF) as a binder solution. AgNPs with BFSF form the conductive porous natural binder layer (CPNBL). It does not allow to increase the resistivity of the deposited material on graphene electrodes and also keeps the nanofibers intact with paper-based SPCIE. The synthesized material of MWCNT-ZnO nanofibers and green synthesized AgNPs with BFSF as a binder were characterized by Ultraviolet-visible spectroscopy (UV–vis), scanning electron microscope (SEM), x-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FTIR). The amperometric measurements were performed on the proposed SPCIE sensor to detect the glucose sample directly. The innovative paper-based SPCIE glucose sensor exhibits a linear corelation between current measurements and glucose concentration in the range between 45.22 μm and 20 mm, with a regression coefficient (R 2) of 0.9902 and a lower limit of detection (LoD) of 45.22 μm (n = 5). The sensitivity of the developed SPCIE sensor was 2178.57 μAmM−1cm−2, and the sensor’s response time determined was approximately equal to 18 s. The proposed sensor was also tested for real blood serum sample, and relative standard deviation (RSD) was found equal to 2.95%.

Impedimetric Early Sensing of Volatile Organic Compounds Released from Li-Ion Batteries at Elevated Temperatures

Lithium-ion batteries prove to be a promising technology for achieving present and future goals regarding energy resources. However, a few cases of lithium-ion battery fires and failures caused by thermal runaway have been reported in various news articles; therefore, it is important to enhance the safety of the batteries and their end users. The early detection of thermal runaway by detecting gases/volatile organic compounds (VOCs) released at the initial stages of thermal runaway can be used as a warning to end users. An interdigitated platinum electrode spin-coated with a sub-micron thick layer of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) showed sensitivity for two VOCs (ethyl-methyl carbonate and methyl formate) released from Li-ion batteries during thermal runaway, as well as their binary mixtures at elevated temperatures, which were measured using impedance spectroscopy over a frequency range of 1 MHz to 1 Hz. The sensor response was tested at three different high temperatures (40 °C, 55 °C, and 70 °C) for single analytes and binary mixtures of two VOCs at 5 ppm, 15 ppm, and 30 ppm concentrations. Equivalent electrical parameters were derived from impedance data. A machine learning approach was used to classify the sensor’s response. Classification algorithms classify the sensor’s response at elevated temperatures for different analytes with an accuracy greater than 70%. The success of the reported sensors will enhance battery safety via the early detection of thermal runaway.

Flexible capacitive pressure sensor based on interdigital electrodes with porous microneedle arrays for physiological signal monitoring

Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibility and wearability. However, their relatively low sensitivity, linearity, and stability have hindered their large-scale commercial application. Herein, a flexible capacitive pressure sensor based on an interdigital electrode structure with two porous microneedle arrays (MNAs) is proposed. The porous substrate that constitutes the MNA is a mixed product of polydimethylsiloxane and NaHCO3. Due to its porous and interdigital structure, the maximum sensitivity (0.07 kPa−1) of a porous MNA-based pressure sensor was found to be seven times higher than that of an imporous MNA pressure sensor, and it was much greater than that of a flat pressure sensor without a porous MNA structure. Finite-element analysis showed that the interdigital MNA structure can greatly increase the strain and improve the sensitivity of the sensor. In addition, the porous MNA-based pressure sensor was found to have good stability over 1500 loading cycles as a result of its bilayer parylene-enhanced conductive electrode structure. Most importantly, it was found that the sensor could accurately monitor the motion of a finger, wrist joint, arm, face, abdomen, eye, and Adam’s apple. Furthermore, preliminary semantic recognition was achieved by monitoring the movement of the Adam’s apple. Finally, multiple pressure sensors were integrated into a 3 × 3 array to detect a spatial pressure distribution. Compared to the sensors reported in previous works, the interdigital electrode structure presented in this work improves sensitivity and stability by modifying the electrode layer rather than the dielectric layer.

Enhanced self-driven ultraviolet photodetection performance of high-k Ta2O5/GaN heterostructure

Recently, high-k dielectric oxide-based MIS type ultraviolet (UV) photodetectors (PDs) have engrossed the researchers in the area of optoelectronics owing to their superior properties. The current work focuses on the preparation of symmetric interdigitated Au electrodes on Ta2O5/GaN heterojunction and to check its functioning as a photosensor in UV region. The impact of post-annealing procedure on the bandgap, crystalline quality, surface morphology and chemical composition has been investigated using UV-VIS, XRD, AFM and XPS techniques, respectively. The evaluated optical bandgaps from the Tauc's plots for the Ta2O5 films ranging from 4.52 eV to 4.92 eV. XRD analysis showed the formation of an orthorhombic phase after post-annealing temperature of 700 °C. The post-annealed Ta2O5 film surface morphology comprises prearranged atomic clusters with spherical shapes. The XPS exploration revealed the occurrence of the Ta5+ state and confirmed the formation of Ta2O5 phase. Photodetection parameters of the designed Au/Ta2O5/GaN MIS BB PDs are studied using I–V, responsivity and temporal responses as a function of the post-annealing process. At 0 V bias, with the illumination of 310 nm UV light, the 800 °C post-annealed MIS PD device exhibited peak responsivity of 212 mA/W, external quantum efficiency (EQE) of 86.8 % and detectivity of 1.5 × 1013 Jones. Further, under self-driven mode with 350 nm light illumination, the 800 °C post-annealed UV PD device generated faster rise and fall times of 90 ms and 790 ms, respectively. The post-annealed Au/Ta2O5/GaN heterostructure PD device demonstrates improved photoresponsivity, EQE and rise/fall times compared with the as-deposited PD device. This remarkable improvement in the photodetection performance is attributed to the best band configuration of the Ta2O5/GaN heterostructure because of substantial post-annealing process and facilitating broadband absorption from UV-C to A region with quicker generation, separation and transportation of photogenerated charge carriers. Consequently, the current research work emphasizes the significance of the combination of UV sensing Ta2O5 high-k oxide and n-GaN materials to serve the future necessities of the photodetection technology under self-driven mode i.e., without any external bias.

Nanocasting technique for imprinting a natural leaf pattern on biomimetic polyaniline to yield an artificial hierarchical surface structure for gas sensing

Hydrogen sulfide (H2S) posed substantial safety risks in industrial settings due to its odorless and toxic nature and necessitated vigilant detection. With the burgeoning importance of H2S gas sensing applications, this study focused on the synthesis and utilization of a novel biomimetic material aimed at advancing gas sensing capabilities. Biomimetic polyaniline (Bio-PANI) with an artificial hierarchical surface structure was fabricated through the innovative nanocasting technique. This technique involved the replication of the surface pattern of a natural Xanthosoma sagittifolium leaf (XSL) onto a PANI coating, achieved using a negative template. In comparison to PANI, Bio-PANI showcased higher specific surface area (160 m2/g versus 41 m2/g of PANI) and exhibited significantly amplified reversible redox and doping–dedoping capacities. The application of Bio-PANI and PANI coatings on interdigitated electrodes (IDEs) allowed for gas-sensing assessments. These evaluations encompassed as-prepared IDE sensor’s responsivity, selectivity, repeatability, and stability. Notably, the Bio-PANI-coated IDE sensor showed larger response (185% versus 27% of PANI toward a 10 ppm concentration of H2S), a consequence of their substantially larger specific surface area and greater electrochemical performances when contrasted with PANI-coated IDE sensor. In addition, Bio-PANI-coated IDE sensor exhibited better selectivity, repeatability, long-term stability, and moisture resistance.

Fabrication and characterization of suspended La0.7Sr0.3MnO3 nanofibers for high-sensitive and fast-responsive infrared bolometer

La1−x Sr x MnO3 manganite oxides have shown great potential for infrared (IR) sensing. In this study, La0.7Sr0.3MnO3 (LSMO) nanofibers, synthesized by a simple electrospinning process, are suspended between gold interdigitated electrode (IDE). These electrodes, which acts as a supporting platform for the dangling nanofiber, are microelectromechanical systems based that can be fabricated quickly and economically with fewer fabrication steps. Due to the large surface-area-to-volume ratio, these fibers have outstanding thermo-electrical properties, which puts them in the leagues of materials suitable for IR sensing. Performance-wise these hanging nanofibers belong to a class of promising thermal sensors due to negligible thermal loss. The optoelectrical characterization shows its temperature coefficient of resistance (TCR) is −1.48%K−1, and its electrical resistance follows an inverse square law for distance from the IR source. The fabricated LSMO nanofibers based microbolometer has a significantly low thermal time constant with average thermal response and recovery time of 63 ms and 77 ms, respectively. Furthermore, they show encouraging bolometric properties with thermal conductance, thermal capacitance, voltage responsivity, and thermal noise limited detectivity of 3.6 × 10−3WK−1, 0.2268 × 10−3JK−1 , 1.96 × 105VW−1, and 3.7 × 108cm Hz1/2W−1 respectively. The high voltage responsivity and TCR, commensurate with the ultralow response and recovery time confirm that the fabricated Microbolometer can find industrial applications as thermal sensors.

The Effect of Anion Modification on the Conductive Polymer/Ag‐Interdigitated Electrodes Micro‐Supercapacitor

Due to their outstanding electrical conductivity, simplicity of synthesis, and exceptional flexibility, conductive polymers are the most attractive electrode materials for micro‐supercapacitors (MSCs). However, when used as an electrode material alone, its poor capacitive performance and cycle‐life hinder the wide engineering applications. Herein, a polypyrrole (PPy)/Ag‐interdigitated electrodes MSCs is proposed, and the impact of aromatic sulfonic acid group anion modification on the electrochemical properties and flexibility of PPy/Ag MSCs is investigated. In the results, it is shown that different aromatic sulfonic‐acid‐based anionic dopants have different effects on the properties of PPy films. Among the prepared three PPy/Ag MSCs devices, PPy:anthraquinone‐2‐sulfonic acid/Ag MSCs have the highest areal capacitance (198.8 mF cm−2) at a current density of 0.5 mA cm−2, surpassing PPy:2‐naphthalenesulfonic acid/Ag MSCs (114.3 mF cm−2) and PPy:p‐toluenesulfonic acid monohydrate/Ag MSCs (89.7 mF cm−2). Furthermore, at a power density of 0.25 mW cm−2, the PPy:AQS/Ag MSCs exhibit a high energy density of 27.61 μWh cm−2, which is above the most of the previously reported PPy‐based MSCs. Therefore, in this research, the groundwork is provided for improving properties of flexible MSCs based on PPy.

Fabrication of robust and cost-efficient Hoffmann-type MOF sensors for room temperature ammonia detection

The development of fast-response sensors for detecting NH3 at room temperature remains a formidable challenge. Here, to address this challenge, two highly robust Hoffmann-type metal-organic frameworks are rationally applied as the NH3 sensing materials which possess ultra-high static adsorption capacity for NH3, only lower than the current benchmark material. The adsorption mechanism is in-depth unveiled by dynamic adsorption and simulation studies. The assembled interdigital electrode device exhibits low detection limit (25 ppb) and short response time (5 s) at room temperature, which set a record among all electrical signal sensors. Moreover, the sensor exhibits excellent selectivity towards NH3 in the presence of 13 other potential interfering gases. Prominently, the sensor can stably output signals for more than two months at room temperature and can be recovered by simply purging nitrogen at room temperature without heating. This study opens up a way for reasonably designing gas sensing materials for toxic gases.

Green synthesized silver nanoparticles functionalized interdigitated electrodes for bacterial sensing using non-faradaic electrochemical impedance spectroscopy

In this study, we present a label-free non-faradaic impedimetric biosensor to detect bacterial cells using microfabricated gold interdigitated electrode (IDE). Silver nanoparticles (AgNP) are green synthesized using aqueous neem extract and characterized using Attenuated Total Reflectance- Fourier Transform Infrared spectra (ATR-FTIR), Dynamic Light Scattering (DLS), Scanning Electron Microscopy (SEM), and UV–Visible spectroscopy techniques. The synthesized AgNPs are well dispersed with an average size of 84 nm and showed an extensive antibacterial property indicated by a standard bioassay against Escherichia coli (E. coli). Gold IDEs are microfabricated by lithography on borosilicate glass wafers. The biofunctionalization of gold IDE is carried out using thiol‑gold covalent chemistry with mercaptohexanol (MCH). The self-assembled monolayer (SAM) of MCH facilitates drop-cast deposition of AgNP on the surface forming an MCH-AgNP. The functionalized IDE is electrochemically stable for further experiments and was validated by open circuit potential measurements. The objective of developing a label-free approach is confirmed by cyclic voltammetry analysis. Non-faradaic electrochemical impedance spectroscopy (nf-EIS) is carried out to detect E.coli cells suspended in water. The antibacterial property of AgNP is exploited to detect the decrease in cell concentration using nf-EIS. The impedance signatures corresponding to the trapping of cells are recorded with respect to time. Bacterial growth is a major challenge in maintaining water quality. The results demonstrated in this work would help to mitigate this problem effectively in a quick time without the need for skilled labor and sophisticated instruments required in traditional antibacterial testing.

Lithography-free interdigitated electrodes by trench-filling patterning on polymer substrate for Alzheimer's disease detection

Microelectrodes have played a crucial role in electrochemistry for the last few decades. However, the conventional lithographic processes, the key players in fabrication, are nonetheless technologically challenging, pricey, and lack reproducibility. In this work has developed a novel and low-cost patterned-replication fabrication technology for interdigitated electrode array (IDA) electrodes on the polymer substrate. Conventional UV-lithography has been utilized to fabricate the nickel IDA electrode pattern as a master mold on the stainless-steel substrate, which was replicated onto the polymer substrate by the hot-emboss technique. Then, gold was deposited on the replicated wafer by electron beam evaporation, and finally adhesive tape lift-off was used to obtain the gold IDA electrode. The fabricated IDA electrode was applied for electrochemical detection of various p-aminophenol (PAP) concentrations as a representative biomarker with a detection limit of 0.01 nM. Finally, different levels of amyloid beta 42 (Aß42) and amyloid beta aggregated (Aß Agg.), two Alzheimer's disease (AD) biomarkers, were measured using the developed IDA electrode via e-ELISA using enzyme by-products PAP. While quantified, the proposed IDA electrode successfully detects Aß42 and Aß Agg. with the lower detection limit (LOD) of 3.9 and 7.81 pg/ml, respectively.

Flexible Optoelectronic Multimodal Proximity/Pressure/Temperature Sensors with Low Signal Interference.

Multimodal tactile sensors are a crucial part of intelligent human-machine interaction and collaboration. Simultaneous detection of proximity, pressure, and temperature on a single sensor can greatly promote the safety, interactivity and compactness of interaction systems. However, severe signal interference and complex decoupling algorithm hinder the actual applications. Here, we report a flexible optoelectronic multimodal sensor capable of detecting and decoupling proximity/pressure/temperature by integrating a light waveguide and an interdigital electrode into a compact fibrous sensor. Negligible signal interference is realized by combining heterogeneous sensing mechanisms of optics and electronics, which encodes proximity into capacitance, pressure into light intensity and temperature into resistance. The sensor exhibited a large sensing distance of 225 mm with fast responses for proximity detection, a pressure sensitivity of 0.42 N-1 , and a temperature sensitivity of 7%/°C. As a proof of concept, the doll equipped with the sensor can accurately discriminate and detect various stimuli, thus achieving safe and immersive interactions with the user. This work opens up promising paths for self-decoupled multimodal sensors and related human/machine/environment interaction applications. This article is protected by copyright. All rights reserved.

NanoIEA: A Nanopatterned Interdigitated Electrode Array-Based Impedance Assay for Real-Time Measurement of Aligned Endothelial Cell Barrier Functions.

A nanopatterned interdigitated electrode array (nanoIEA)-based impedance assay is developed for quantitative real-time measurement of aligned endothelial cell (EC) barrier functions in vitro. A bioinspired poly(3,4-dihydroxy-L-phenylalanine) (poly (l-DOPA)) coating is applied to improve the human brain EC adhesion onto the Nafion nanopatterned surfaces. It is found that a poly (l-DOPA)-coated Nafion grooved nanopattern makes the human brain ECs orient along the nanopattern direction. Aligned human brain ECs on Nafion nanopatterns exhibit increased expression of genes encoding tight and adherens junction proteins. Aligned human brain ECs also have enhanced impedance and resistance versus unaligned ones. Treatment with a glycogen synthase kinase-3 inhibitor (GSK3i) further increases impedance and resistance, suggesting synergistic effects occur on the cell-cell tightness of in vitro human brain ECs via a combination of anisotropic matrix nanotopography and GSK3i treatment. It is found that this enhanced cell-cell tightness of the combined approach is accompanied by increased expression of claudin protein. These data demonstrate that the proposed nanoIEA assay integrated with poly (l-DOPA)-coated Nafion nanopatterns and interdigitated electrode arrays can make not only biomimetic aligned ECs, but also enable real-time measurement of the enhanced barrier functions of aligned ECs via tighter cell-cell junctions.