Transduction Layer Research Articles

Printing technologies for the fabrication of ion-selective electrodes

The fabrication of ion-selective electrodes (ISEs) via printing technologies such as screen-printing, inkjet printing, and 3D printing is attracting increasing attention due to the superb reproducibility and scalability of these technologies. In contrast to traditional manual casting, coating, and assembling procedures often used in research labs, printing methods are much more compatible with manufacturing processes in industry and, therefore, are easier to scale up. In this paper, we first summarized and compared the printing mechanisms and ink requirements of screen printing, inkjet printing, and 3D printing technologies. Then we present an overview of how different printing technologies can create sensor components, such as electrical contact layers, ion-to-electron transduction layers, ion sensing membranes, reference electrode membranes, insulation layers, and microfluidic/detection housings. The printing protocol, ink material, and sensor performance are highlighted for a few selected ISEs. This review concludes with a summary of the advantages and drawbacks of various printing technologies.

Tailored Polypyrrole Nanofibers as Ion-to-Electron Transduction Membranes for Wearable K+ Sensors.

Conductive polymers are recognized as ideal candidates for the development of noninvasive and wearable sensors for real-time monitoring of potassium ions (K+) in sweat to ensure the health of life. However, the low ion-to-electron transduction efficiency and limited active surface area hamper the development of high-performance sensors for low-concentration K+ detection in the sweat. Herein, a wearable K+ sensor is developed by tailoring the nanostructure of polypyrrole (PPy), serving as an ion-to-electron transduction layer, for accurately and stably tracing the K+ fluctuation in human sweat. The PPy nanostructures can be tailored from nanospheres to nanofibers by controlling the supramolecular assembly process during PPy polymerization. Resultantly, the ion-to-electron transduction efficiency (17-fold increase in conductivity) and active surface area (1.3-fold enhancement) are significantly enhanced, accompanied by minimized water layer formation. The optimal PPy nanofibers-based K+ sensor achieved a high sensitivity of 62mVdecade-1, good selectivity, and solid stability. After being integrated with a temperature sensor, the manufactured wearable sensor realized accurate monitoring of K+ fluctuation in the human sweat.

Ion-Electron Transduction Layer of the SnS2-MoS2 Heterojunction to Elevate Superior Interface Stability for All-Solid Sodium-Ion Selective Electrode.

The high selectivity and fast ion response of all-solid sodium ion selective electrodes were widely applied in human sweat analysis. However, the potential drift due to insufficient interfacial capacitance leads to the deterioration of its stability and ultimately affects the potential accuracy of ion analysis. Designing a novel ion-electron transduction layer between the electrode and the ion selective membrane is an effective method to stabilize the interfacial potential. Herein, the SnS2-MoS2 heterojunction material was constructed by doping Sn in MoS2 nanosheets and used as the ion electron transduction layers of an all-solid sodium ion selective electrode for the first time, achieving the stable and efficient detection of Na+ ions. The proposed electrode exhibited a Nernst slope of 57.86 mV/dec for the detection of Na+ ions with a detection limit of 10-5.7 M in the activity range of 10-6-10-1 M. Via the electronic interaction at the heterojunction interfaces between SnS2 and MoS2 materials, the micro-nanostructure of the SnS2-MoS2 heterojunction was changed and SnS2-MoS2 as the ion-electron transduction layer acquired excellent capacitance (699 μF) and hydrophobicity (132°), resulting in a long-term potential stability of 1.37 μV/h. It was further proved that the large capacitance and high hydrophobicity of the ion-electron transduction layer are primary reasons for the excellent stability of the all-solid sodium ion selective electrode toward Na+ ions.

Non-Equilibrium Nitrate Detection in Ionophore-Based Solid-Contact Ion-Selective Electrodes

Ion-selective electrodes (ISE’s) have benefits for solution-phase detection and quantification of ions, such as ease of operation, low cost, and high throughput compared to, e.g., ion chromatography or mass spectrometry methods. ISE devices are traditionally operated under zero-current conditions, where analyte ions passively exchange across a selective membrane barrier, yielding a Nernstian response after equilibration of Coulombic and chemical driving forces across the membrane. However, this passive mode of operation can require long equilibration times and lead to drift, for example due to electrolyte leakage and pH impacting the membrane and reference electrode. In recent years, non-equilibrium detection techniques have been of growing interest, where the ISE signal is obtained under applied electrical signal. However, the majority of this work has been devoted to cation sensing, with relatively few studies examining anion ISEs under active electrical actuation. Agricultural expansion and the corresponding uptick in application of supplemental nitrogen to soil has led to an increased demand for technologies to measure anions like nitrate – both from a production and regulation standpoint. In this work, we employ galvanostatic polarization of solid-contact ISEs as a non-equilibrium nitrate detection method. Our investigation involves coating electrodes with a redox-active charged polymer to act as a transduction layer to convert ionic to electronic signal, followed by solvent casting of a polymeric ion-selective membrane. We examine the impact of repeated rapid charging and discharging ISE electrode stacks on measurement time and stability. We compare the metrics derived from this technique to conventional open-circuit measurements using the same device. We identify benefits for this mode of operation using established nitrate membrane materials (e.g. nitrate ionophore VI membrane cocktail) that address some of the typical limitations of these conventional materials and we discuss opportunities for further refinement.

A Fiber Sensor for Long-Term Monitoring of Extracellular Potassium Ion Fluctuations in Chronic Neuropsychiatric Diseases.

The extracellular potassium ion concentration in the brain exerts a significant influence on cellular excitability and intercellular communication. Perturbations in the extracellular potassium ion level are closely correlated with various chronic neuropsychiatric disorders including depression. However, a critical gap persists in performing real-time and long-term monitoring of extracellular potassium ions, which is necessary for comprehensive profiling of chronic neuropsychiatric diseases. Here, a fiber potassium ion sensor (FKS) that consists of a soft conductive fiber with a rough surface and a hydrophobic-treated transduction layer interfaced with a potassium ion-selective membrane is found to solve this problem. The FKS demonstrates stable interfaces between its distinct functional layers in an aqueous environment, conferring an exceptional stability of 6 months in vivo, in stark contrast to previous reports with working durations from hours to days. Upon implantation into the mouse brain, the FKS enables effective monitoring of extracellular potassium ion dynamics under diverse physiological states including anesthesia, forced swimming, and tail suspension. Using this FKS, tracking of extracellular potassium ion fluctuations that align with behaviors associated with the progression of depression over months is achieved, demonstrating its usability in studying chronic neuropsychiatric disorders from a new biochemical perspective.

Screen-Printed Wearable Sweat Sensor for Cost-Effective Assessment of Human Hydration Status through Potassium and Sodium Ion Detection.

Human sweat is intricately linked to human health, and unraveling its secrets necessitates a substantial volume of experimental data. However, conventional sensors fabricated via complex processes such as photolithography offer high detection precision at the expense of prohibitive costs. In this study, we presented a cost-effective and high-performance wearable flexible sweat sensor for real-time monitoring of K+ and Na+ concentrations in human sweat, fabricated using screen printing technology. Initially, we evaluated the electrical and electrochemical stability of the screen-printed substrate electrodes, which demonstrated good consistency with a variation within 10% of the relative standard deviation (RSD), meeting the requirements for reliable detection of K+ and Na+ in human sweat. Subsequently, we employed an "ion-electron" transduction layer and an ion-selective membrane to construct the sensors for detecting K+ and Na+. Comprehensive tests were conducted to assess the sensors' sensitivity, linearity, repeatability, resistance to interference, and mechanical deformation capabilities. Furthermore, we evaluated their long-term stability during continuous monitoring and storage. The test results confirmed that the sensor's performance indicators, as mentioned above, met the requirements for analyzing human sweat. In a 10-day continuous and regular monitoring experiment involving volunteers wearing the sensors, a wealth of data revealed a close relationship between K+ and Na+ concentrations in human sweat and hydration status. Notably, we observed that consistent and regular physical exercise effectively enhanced the body's resistance to dehydration. These findings provided a solid foundation for conducting extensive experiments and further exploring the intricate relationship between human sweat and overall health. Our research paved a practical and feasible path for future studies in this domain.

Potential stability improvement in solid-contact Pb2+ ion-selective electrodes by using polyaniline/montmorillonite composites as the ion-to-electron transducer

This work demonstrates a sensitive and stable solid contact ion selective electrode (SC-ISE) constructed using a polyaniline intercalated hydrophobic montmorillonite composite (PANI-DMT) as a solid transduction layer for the detection of lead ions. A detection limit of 1.0 × 10−7 M and fast potential response (<5 s) were realized using the GC/PANI-DMT/Pb2+-ISM. In addition, the Pb2+ ISE based on PANI-DMT exhibited high stability and E0 reproducibility (±0.6 mV). The potential drift of GC/PANI-DMT/Pb2+-ISM under ± 1 nA constant current and open circuit potential was as low as (9.4 ± 4.6) × 103 μV/h and 25.3 ± 3.5 μV/h, respectively. The outstanding stability and reproducibility of GC/PANI-DMT/Pb2+-ISM is attributed to an effective ion diffusion channel provided by DMT, the larger specific capacitance (465 μF), and improved hydrophobicity of PANI-DMT composites compared to PANI. Importantly, the GC/PANI-DMT/Pb2+-ISM was stable under the external interference of O2, N2, and light, suggesting promise for Pb2+ detection in various applications.

Theoretical Modeling of Piezoelectric Micromachined Ultrasonic Transducers With Honeycomb Structure

In this work, we reported a theoretical model for a novel piezoelectric micromachined ultrasonic transducer (PMUT). The sensing cells with hexagonal transduction diaphragms in the PMUT array are designed and arranged in a bioinspired honeycomb structure. Based on the classical piece-wise approach commonly used for PMUT with circular diaphragm, an enhanced theoretical model is developed. In this model, the deflection of the honeycomb diaphragm is analytically determined by the volume deflection, rather than the path deflection commonly used in the previous models. The hexagonal diaphragm is converted as a circular one, whose radius is derived by correcting the characteristic size of the hexagonal diaphragm multiplied by a correction factor. The calculated parameters by the reported theoretical model of a transduction cell in the PMUT array, such as resonant frequency and static deflection, matched well with the data obtained by finite element analysis and experiment. Special investigations are made on the effects of top electrode coverage and transduction layer thickness towards PMUT’s performance. The reported theoretical model in this work is suitable not only for PMUTs with circular and hexagonal transduction cells, but also for square and other arbitrary shape diaphragms. This enhanced theoretical model provides an interesting insight on design optimizations of PMUT with various transduction cell geometries. [2022-0093]

In Situ Monitoring of Extracellular K+ Using the Potentiometric Mode of Scanning Electrochemical Microscopy with a Carbon-Based Potassium Ion-Selective Tip.

The expression of potassium channels can be related to the occurrence and development of tumors. Their change would affect K+ outflow. Thus, in situ monitoring of extracellular K+ shows a great significance. Herein, the dual-functional K+ ion-selective electrode as the scanning electrochemical microscopy (SECM) tip (K+-ISE SECM tip) has been developed for in situ monitoring of the extracellular K+. Based on multi-wall carbon nanotubes as a transduction layer, the K+-ISE SECM tip realizes both the plotting of approach curves to position the tip for in situ detection and the recording of potential responses. It shows a near Nernstian response, good selectivity, and excellent stability. Based on these characteristics, it was used to in situ monitor K+ concentrations ([K+]o) of three breast cancer cell lines (MCF-7, MDA-MB-231, and SK-BR-3 cells) at 3 μm above the cell, and [K+]o of MDA-MB-231 cells show the highest value, followed by MCF-7 cells and SK-BR-3 cells. K+ outflow induced by electrical stimulation or pH changes of the culture environment (Δ[K+]o) was further determined, and the possible mechanism of K+ outflow was investigated with 4-aminopyridin (4-AP). MCF-7 cells present the largest value of Δ[K+]o, followed by MDA-MB-231 cells and SK-BR-3 cells at all the stimulation potentials, and pH 6.50 shows the greatest impact on K+ outflow of the three cell lines. The pretreatment of 4-AP changed K+ outflow, probably due to the regulation of voltage-gated channels. These findings provide insight into a deep understanding of the microenvironment influence on K+ outflow, thereby reflecting the possible mechanism of potassium channels.

A Layered View on Focal Adhesions

Simple SummaryThe cytoskeleton is a network of protein fibres within cells that provide structure and support intracellular transport. Focal adhesions are protein complexes associated with the outer cell membrane that are found at the ends of specialised actin fibres of this cytoskeleton. They mediate cell adhesion by connecting the cytoskeleton to the extracellular matrix, a protein and sugar network that surrounds cells in tissues. Focal adhesions also translate forces on actin fibres into forces contributing to cell migration. Cell adhesion and migration are crucial to diverse biological processes such as embryonic development, proper functioning of the immune system or the metastasis of cancer cells. Advances in fluorescence microscopy and data analysis methods provided a more detailed understanding of the dynamic ways in which proteins bind and dissociate from focal adhesions and how they are organised within these protein complexes. In this review, we provide an overview of the advances in the current scientific understanding of focal adhesions and summarize relevant imaging techniques. One of the key insights is that focal adhesion proteins are organised into three layers parallel to the cell membrane. We discuss the relevance of this layered nature for the functioning of focal adhesion.The cytoskeleton provides structure to cells and supports intracellular transport. Actin fibres are crucial to both functions. Focal Adhesions (FAs) are large macromolecular multiprotein assemblies at the ends of specialised actin fibres linking these to the extracellular matrix. FAs translate forces on actin fibres into forces contributing to cell migration. This review will discuss recent insights into FA protein dynamics and their organisation within FAs, made possible by advances in fluorescence imaging techniques and data analysis methods. Over the last decade, evidence has accumulated that FAs are composed of three layers parallel to the plasma membrane. We focus on some of the most frequently investigated proteins, two from each layer, paxillin and FAK (bottom, integrin signalling layer), vinculin and talin (middle, force transduction layer) and zyxin and VASP (top, actin regulatory layer). Finally, we discuss the potential impact of this layered nature on different aspects of FA behaviour.

Using MoS2/Fe3O4 as Ion-Electron Transduction Layer to Manufacture All-Solid-State Ion-Selective Electrode for Determination of Serum Potassium

As an essential electrolyte for the human body, the potassium ion (K+) plays many physiological roles in living cells, so the rapid and accurate determination of serum K+ is of great significance. In this work, we developed a solid-contact ion-selective electrode (SC-ISE) using MoS2/Fe3O4 composites as the ion-to-electron transducer to determine serum K+. The potential response measurement of MoS2/Fe3O4/K+-ISE shows a Nernst response by a slope of 55.2 ± 0.1 mV/decade and a low detection limit of 6.3 × 10−6 M. The proposed electrode exhibits outstanding resistance to the interference of O2, CO2, light, and water layer formation. Remarkably, it also presents a high performance in potential reproducibility and long-term stability.

Cure monitoring and damage identification of CFRP using embedded piezoelectric sensors network

Because of the advantages of high specific strength and high specific stiffness, carbon fiber reinforced plastics (CFRP) have been the most ideal materials in the field of civil aviation. Cure monitoring in manufacturing process and damage identification in service stage of CFRP are always hot topics. The Semi-Analytical Finite Element (SAFE) method and micromechanical model are employed to analyse the propagation characteristics of the Lamb-like waves in a continuous flat aluminium plate attached to a viscoelastic unidirectional CFRP in semi-infinite half-space. Then the vacuum bag moulding process of prepregs is monitored using Fiber Bragg Grating (FBG) and piezoelectric sensors encapsulated in Stanford Multiactuator-Receiver Transduction (SMART) Layer. The calculated energy velocities and attenuations of guided waves show the same trends with the numerical results while curing. After the CFRP is demoulded, the damage identification experiments are carried out. By continuing to use the sensor network embedded in the manufacturing phase, the artificial damages can be precisely located. The results demonstrated that the life-cycle monitoring of CFRP can be achieved effectively by the piezoelectric sensors network.

Potassium-Selective Solid-Contact Electrode with High-Capacitance Hydrous Iridium Dioxide in the Transduction Layer.

This work presents new material for solid-contact layers—hydrous iridium dioxide IrO2·2H2O, characterized by high electrical capacitance value, evaluated using chronopotentiometry (1.22 mF) and electrochemical impedance spectroscopy (1.57 mF). The remarkable electrical parameters of layers resulted in great analytical parameters of IrO2·2H2O-contacted potassium-selective electrodes. Various parameters of ion-selective electrodes were examined in the scope of this work using a potentiometry method including: linear range, repeatability, stability of potentiometric response and sensitivity to varying measurement conditions. The analytical parameters obtained for solid-contact electrodes were compared with the ones obtained for coated disc electrodes to evaluate the influence of the iridium dioxide layer. The linear range of the IrO2·2H2O-contacted K+-selective electrodes covered concentrations of K+ ions from 10−6 to 10−1 M and the potential stability was estimated at 0.097 mV/h. The IrO2·2H2O-contacted electrodes turned out to be insensitive to varying light exposure and changes in the pH values of measured solutions (in the pH range of 2 to 10.5). A water layer test proved that, contrary to the coated disc electrode, the substantial water film is not formed between the ion-selective membrane and iridium dioxide layer.

PVDF/ZnO hybrid nanocomposite applied as a resistive humidity sensor

Polyvinyledene fluoride (PVDF), an aliphatic polymer with massive hydrophobic groups, has been developed as humidity sensitive material (hydrophilic) using an additive of ZnO nanoparticles as resistant transduction layers, an PVDF/ZnO nanocomposite bas been prepared as humidity sensor through a simple hydrothermal approach. PVDF/ZnO nanocomposite have been fabricated by spin coating method and characterized by XRD, FE-SEM, TEM, BET, UV-Vis spectra and PL spectra. Owing to its 2D replicated structure with rod-like nanocomposite, the PVDF/ZnO provide more water molecules adsorption and desorption across the humidity sensor surface compare than pure ZnO nanoparticles. The humidity sensing properties was established by using saturated salt solutions and the relative humidity range of 5-95% were achieved at 35°C. The experimental results confirmed that the sensitivity factor (Sf) of PVDF/ZnO nanocomposite humidity sensor exhibit 3 order of magnitude variation than that of pure PVDF and good linearity compare than pure ZnO nanoparticles. The response and recovery times of the nanocomposite based humidity sensor are to be 30 s and 51 s, respectively. The performance of PVDF/ZnO nanocomposite sensor can be improved by PVDF modifier on ZnO nanoparticles, because the PVDF/ZnO nanocomposite have more surface oxygen vacancy defects was synthesized by hydrothermal method. The experimental analysis indicates that the enhanced humidity sensitivity was probably due to BET surface area and provides more water adsorption sites in hybrid nanocomposite. These results open the door for a new idea for high performance and promising 2D nanocomposite materials in the development of sensitive RH% sensor for potential in the manufacture of humidity sensors.

A post-invasion role for Chlamydia type III effector TarP in modulating the dynamics and organization of host cell focal adhesions

The human pathogen Chlamydia trachomatis targets epithelial cells lining the genital mucosa. We observed that infection of various cell types, including fibroblasts and epithelial cells resulted in the formation of unusually stable and mature focal adhesions that resisted disassembly induced by the myosin II inhibitor, blebbistatin. Superresolution microscopy revealed in infected cells the vertical displacement of paxillin and focal adhesion kinase from the signaling layer of focal adhesions, whereas vinculin remained in its normal position within the force transduction layer. The candidate type III effector TarP, which localized to focal adhesions during infection and when expressed ectopically, was sufficient to mimic both the reorganization and blebbistatin-resistant phenotypes. These effects of TarP, including its localization to focal adhesions, required a post-invasion interaction with the host protein vinculin through a specific domain at the C terminus of TarP. This interaction is repurposed from an actin-recruiting and -remodeling complex to one that mediates nanoarchitectural and dynamic changes of focal adhesions. The consequence of Chlamydia-stabilized focal adhesions was restricted cell motility and enhanced attachment to the extracellular matrix. Thus, via a novel mechanism, Chlamydia inserts TarP within focal adhesions to alter their organization and stability.

Assessments of Structural Health Monitoring for Fatigue Cracks in Metallic Structures by Using Lamb Waves Driven by Piezoelectric Transducers

In this paper, the assessments of structural health monitoring (SHM) for metallic structures are presented. Tests were conducted on three specimens for fatigue crack testing and damage index measurements. In each specimen, a transducer array of six Stanford Multiactuator-Receiver Transduction (SMART) Layers, each of which contains a piezoelectric transducer, was mounted near the fatigue crack. The Lamb wave was driven by one SMART Layer and received by another. The transducer array generated nine forward and nine backward propagating paths. The damage index defined in the first arrival window (FAW) was obtained for each path. In this work, we propose an averaging process to obtain average damage index from the transducer array. The Lamb waves with various driving frequencies were tested to conduct the performance of the damage monitoring. The results show that the plot of the average damage index versus the actual crack length reveals a narrow band, indicating a small standard deviation of the measurement data. The data of numerous crack lengths and Lamb wave paths are processed statistically to determine the probability of detection (POD) of this damage detection method. It was found that the Lamb wave with the driving frequency of f=450 kHz performed best in the crack monitoring. By using an threshold damage index DIth=0.01, the detectable crack sizes a50/50, a90/50, and a90/95 for the case of f=450 kHz are 4.83, 5.79, and 5.92 mm, respectively. Based on the proposed approach, the relations between the damage index and actual crack length and the POD curves can be applicable to a real structure with the same geometry.

Sensitive Detection of Motor Neuron Disease Derived Exosomal miRNA Using Electrocatalytic Activity of Gold‐Loaded Superparamagnetic Ferric Oxide Nanocubes

AbstractDysregulated microRNA associated pathways contribute to the pathology of neurological disorders, hence presenting themselves as a potential candidate for motor neuron disease (MND) diagnosis. Herein, we reported an enzymatic amplification‐free approach for the electrochemical detection of exosomal microRNA (miR‐338‐3p) from preconditioned media of motor neurons obtained from amyotrophic lateral sclerosis (ALS) patients and healthy controls. Our assay utilizes a three‐step strategy that involves i) initial isolation and purification of exosomal miR‐338‐3p from patients and healthy controls using biotinylated complementary capture probe followed by heat‐release of the specific target, ii) direct adsorption of target miR‐338‐3p onto the gold‐loaded ferric oxide nanocatalyst (AuNP‐Fe2O3NC) through affinity interaction between microRNA and exposed gold surfaces within the AuNP‐Fe2O3NC, and iii) gold nanocatalyst‐induced electrocatalytic signal amplification through methylene blue‐ferricyanide redox cycling (MB/[Fe(CN)6]3−). The electrocatalytic signal is monitored by using chronocoulometry at the AuNP–Fe2O3NC‐modified screen‐printed carbon electrode (AuNP‐Fe2O3NC/SPCE). We demonstrated the detection of miR‐338‐3p as low as 100 aM in spiked buffer samples with a relative standard deviation of (%RSD) &lt;5.0 % (n=5). We also demonstrate the successful detection of miR‐338‐3p from a small cohort of preconditioned media of motor neurons obtained from ALS patients and healthy controls. The sensor avoids the use of conventional recognition and transduction layers in hybridization‐based electrochemical miRNA biosensors, polymerase‐based amplifications. It is robust, fast (&lt;2.5 h) and potentially applicable to a wide variety of RNA biomarker detection.

PHIP drives glioblastoma motility and invasion by regulating the focal adhesion complex

The invasive behavior of glioblastoma is essential to its aggressive potential. Here, we show that pleckstrin homology domain interacting protein (PHIP), acting through effects on the force transduction layer of the focal adhesion complex, drives glioblastoma motility and invasion. Immunofluorescence analysis localized PHIP to the leading edge of glioblastoma cells, together with several focal adhesion proteins: vinculin (VCL), talin 1 (TLN1), integrin beta 1 (ITGB1), as well as phosphorylated forms of paxillin (pPXN) and focal adhesion kinase (pFAK). Confocal microscopy specifically localized PHIP to the force transduction layer, together with TLN1 and VCL. Immunoprecipitation revealed a physical interaction between PHIP and VCL. Targeted suppression of PHIP resulted in significant down-regulation of these focal adhesion proteins, along with zyxin (ZYX), and produced profoundly disorganized stress fibers. Live-cell imaging of glioblastoma cells overexpressing a ZYX-GFP construct demonstrated a role for PHIP in regulating focal adhesion dynamics. PHIP silencing significantly suppressed the migratory and invasive capacity of glioblastoma cells, partially restored following TLN1 or ZYX cDNA overexpression. PHIP knockdown produced substantial suppression of tumor growth upon intracranial implantation, as well as significantly reduced microvessel density and secreted VEGF levels. PHIP copy number was elevated in the classical glioblastoma subtype and correlated with elevated EGFR levels. These results demonstrate PHIP's role in regulating the actin cytoskeleton, focal adhesion dynamics, and tumor cell motility, and identify PHIP as a key driver of glioblastoma migration and invasion.

Quarter-mm2 High Dynamic Range Silicon Capacitive Accelerometer With a 3D Process

A new 3D process is proposed for inertial MEMS sensors where a thin transduction layer based on high-density surface-varying comb fingers, with nano-metric gaps, is patterned below a thick seismic mass layer. The objective is to achieve high-performance in a reduced footprint. An in-plane accelerometer is designed, fabricated with this new 3D process, and tested under acceleration. Initial fabricated devices demonstrate a full-scale range of ±160 g, $7~\mu {g}/ \sqrt {\textit {Hz}}$ Brownian noise floor and more than 4 kHz bandwidth. These figures translate into a dynamic range of more than 150 dB (normalized to 1-Hz bandwidth) with an overall footprint of only ${400}\times {600}\,\,\mu {m}^{{2}}$ .

A Molecularly Imprinted Polymer-Graphene Sensor Antenna Hybrid for Ultra Sensitive Chemical Detection

A state-of-the-art gas sensor is developed to measure extremely small concentrations of a chemical vapor in the air in a range lower than 0.1 parts per billion. The sensor enables simultaneous measurement of a chemical (methyl salicylate) with a resonant electromagnetic structure and radiating the information back to a base station. The chemical sensor is composed of a layer of graphene (transduction layer) with a molecular imprinting polymer (MIP) layer (sensor) on top. This leads to a combination of the ultra high sensitivity of graphene with the exquisite selectivity of the molecular imprinting technique (MIT). The sensor is electrically embedded within a patch antenna. The simulation results using Ansoft high-frequency structure simulator (HFSS) are presented along with test data that show parts per trillion (ppt) detection levels.