Addressable Electrodes Research Articles

Developing Microelectrode Arrays for the Point-of-Care Multiplex Detection of Metabolites.

DNA-aptamer-functionalized electrode arrays can provide an intriguing method for detecting pathogen-derived exometabolites. This work addresses the limitations of previous aptamer-based pathogen detection methods by introducing a novel surface design that bridges the gap between initial efforts in this area and the demands of a point-of-care device. Specifically, the use of a diblock copolymer coating on a high-density microelectrode array and Cu-mediated cross coupling reactions that allow for the exclusive functionalization of that coating by any electrode or set of electrodes in the array provides a device that is stable for 1 year and compatible with the multiplex detection of small-molecule targets. The new chemistry developed allows one to take advantage of a large number of electrodes in the array with one experiment described herein capitalizing on the use of 960 individually addressable electrodes.

Interpenetrated Structures for Enhancing Ion Diffusion Kinetics in Electrochemical Energy Storage Devices

HighlightsA new and compact device configuration was created with two interpenetrated, individually addressable electrodes, allowing precise control over the geometric features and interactions between the electrodes.The interpenetrated electrode design improves ion diffusion kinetics in electrochemical energy storage devices by shortening the ion diffusion length and reducing ion concentration inhomogeneity.The device with interpenetrated electrodes outperformed the traditional separate electrode configuration, enhancing both volumetric energy density and capacity retention rate.

An Electrochemically Programmable Metasurface with Independently Controlled Metasurface Pixels at Optical Frequencies.

Metasurfaces have revolutionized optical technologies by offering powerful, compact, and versatile solutions to control light. Conducting polymers, characterized by their conjugated molecular structures, facilitate charge transport and exhibit interesting electrical, optical, and mechanical properties. Integrating conducting polymers with optical metasurfaces can unlock new opportunities and functionalities in modern optics. In this work, we demonstrate an electrochemically programmable metasurface with independently controlled metasurface pixels at optical frequencies. Electrochemical modulation of locally conjugated polyaniline on gold nanorods, which are arranged on addressable electrodes according to the Pancharatnam-Berry phase design, enables dynamic control over the metasurface pixels into programmable configurations. With the same metasurface device, we showcase diverse optical functions, including dynamic beam diffraction and varifocal lensing along and off the optical axis. The synergy between flat optics and conducting polymer science holds immense potential to enhance the performance and function versatility of metasurfaces, paving the way for innovative optical applications.

Integrated biosensor array for multiplex biomarkers cancer diagnosis via in-situ self-assembly carbon nanotubes with an ordered inverse-opal structure

To enhance the precision and reliability of early disease detection, especially in malignancies, an exhaustive investigation of multi-target biomarkers is essential. In this study, an advanced integrated electrochemical biosensor array that demonstrates exceptional performance was constructed. This biosensor was developed through a controllable porous-size mechanism and in-situ modification of carbon nanotubes (CNTs) to quantify multiplex biomarkers—specifically, C-reaction protein (CRP), carbohydrate antigen 125 (CA125), and carcinoembryonic antigen (CEA)—in human serum plasma. The fabrication process involved creating a highly ordered three-dimensional inverse-opal structure with the CNTs (pCNTs) modifier through microdroplet-based microfluidics, confined spatial self-assembly of nanoparticles, and chemical wet-etching. This innovative approach allowed for direct in-situ modification of nanomaterial onto the surface of electrode array, eliminating secondary transfer and providing exceptional control over structure and stability. The outstanding electrochemical performance was achieved through the synergistic effect of the pCNTs nanomaterial, aptamer, and horseradish peroxidase-labeled (HRP-) antibody. Additionally, the integrated biosensor array platform comprised multiple individually addressable electrode units (n = 11), enabling simultaneous multi-parallel/target testing, thereby ensuring accuracy and high throughput. Crucially, this integrated biosensor array accurately quantified multiplex biomarkers in human serum, yielding results comparable to commercial methods. This integrated technology holds promise for point-of-care testing (POCT) in early disease diagnosis and biological analysis.

Development of a Multiplexed Electrochemical Aptasensor for the Detection of Cyanotoxins.

In this study, we report a multiplexed platform for the simultaneous determination of five marine toxins. The proposed biosensor is based on a disposable electrical printed (DEP) microarray composed of eight individually addressable carbon electrodes. The electrodeposition of gold nanoparticles on the carbon surface offers high conductivity and enlarges the electroactive area. The immobilization of thiolated aptamers on the AuNP-decorated carbon electrodes provides a stable, well-orientated and organized binary self-assembled monolayer for sensitive and accurate detection. A simple electrochemical multiplexed aptasensor based on AuNPs was designed to synchronously detect multiple cyanotoxins, namely, microcystin-LR (MC-LR), Cylindrospermopsin (CYL), anatoxin-α, saxitoxin and okadaic acid (OA). The choice of the five toxins was based on their widespread presence and toxicity to aquatic ecosystems and humans. Taking advantage of the conformational change of the aptamers upon target binding, cyanotoxin detection was achieved by monitoring the resulting electron transfer increase by square-wave voltammetry. Under the optimal conditions, the linear range of the proposed aptasensor was estimated to be from 0.018 nM to 200 nM for all the toxins, except for MC-LR where detection was possible within the range of 0.073 to 150 nM. Excellent sensitivity was achieved with the limits of detection of 0.0033, 0.0045, 0.0034, 0.0053 and 0.0048 nM for MC-LR, CYL, anatoxin-α, saxitoxin and OA, respectively. Selectivity studies were performed to show the absence of cross-reactivity between the five analytes. Finally, the application of the multiplexed aptasensor to tap water samples revealed very good agreement with the calibration curves obtained in buffer. This simple and accurate multiplexed platform could open the window for the simultaneous detection of multiple pollutants in different matrices.

Abstract 7240: Intratumor delivery of plasmid DNA encoding immune stimulating agents induces both local and systemic responses

Abstract Immune checkpoint inhibitors (ICIs) have significant clinical benefits, but are limited by both primary and acquired resistance. The absence of T cells within the tumor microenvironment (TME) is a significant hurdle, reducing the efficacy of ICIs against solid tumors. Multiple studies have been initiated to modify the TME to enhance the effectiveness of ICIs. We previously demonstrated that the intratumor delivery of a plasmid encoding interleukin-12 (pIL-12) using gene electrotransfer (GET) resulted in a significant increase in T effector cells and a reduction in T regulatory cells and myeloid derived suppressor cells within the TME, inducing a robust immune response. Combining pIL-12 GET with ICIs resulted in local and systemic responses in both preclinical and clinical studies. While encouraging results were obtained, improvements were possible. For example, the established GET technology requires high applied voltage for plasmid delivery. In addition, satisfactory delivery cannot be immediately detected. Our current research has focused on developing the next generation GET technology to overcome these issues. This new system includes a pulse generator, a heat source and a tissue impedance measuring device. An array that incorporates independently addressable electrodes was also developed. A moderate elevation of the tissue temperature coupled with the electrode array enabled a 75% reduction in the applied voltage. We tested the approach in the B16.F10 mouse melanoma model. Delivery of pIL-12 with the new system resulted in 100% long-term complete regression and 100% protection from challenge. In addition, monitoring impedance within each independent section of the electrode array revealed different pulse numbers were needed to achieve delivery in each section. We next evaluated a combination therapy, pIL-12 plasmid combined with a plasmid encoding a PD1 peptide, delivered with the next-gen device. In a multi-tumor model, the plasmids were delivered to the subcutaneous tumor; tumors generated with an intraperitoneal injection were untreated. This new therapy induced complete regression of the subcutaneous tumor and blockage of peritoneal tumor growth as assessed via in vivo imaging. Peritoneal tumor growth was not affected by single plasmid delivery or when both plasmids were delivered with the established GET technology. Work is ongoing to translate this approach to clinical evaluation. Citation Format: Richard Heller, Loree C. Heller, Guilan Shi, Jody Synowiec, Julie Singh, Alex Otten, Mark J. Jaroszeski. Intratumor delivery of plasmid DNA encoding immune stimulating agents induces both local and systemic responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 7240.

Bipolar Clark-Type Oxygen Electrode Arrays for Imaging and Multiplexed Measurements of the Respiratory Activity of Cells.

Various miniature Clark-type oxygen electrodes (COEs), which are typically used to measure dissolved oxygen (DO) concentration in cellular respiration, have been developed since the 1980s. Arrays with individually addressable electrodes that constitute the sensor were used for various applications. However, the large number of leads and contact pads required for connecting the electrodes and the external instrument complicate the electrode layout and make the operation of integrated COE arrays challenging. Here, we fabricated closed bipolar electrochemical systems comprising 6 × 8 and 4 × 4 arrays of COEs for imaging and multiplexed detection. The cathodic compartment was sealed with a hydrophobic oxygen-permeable membrane to separate the internal electrolyte solution from the sample solutions. Using the bipolar Clark-type oxygen electrode (BCOE) arrays and electrochemiluminescence (ECL), we measured the DO concentration at each cathode. The results revealed that the ECL intensity changed linearly with the DO concentration. In addition, we used ECL imaging to investigate the respiratory activity of Escherichia coli (E. coli) and Pseudomonas aeruginosa (P. aeruginosa) in suspensions with different cell densities. The ECL images showed that the ECL intensity changed noticeably with the bacterial density. The bacterial respiratory activity was then qualitatively analyzed based on the ECL images acquired successively over a time duration. Further, we measured the antibiotic efficacy of piperacillin, oxacillin, gentamicin, and cefmetazole against E. coli and P. aeruginosa using the BCOE. We found that the ECL intensity increased with the antibiotic concentration, thus indicating the suppression of the bacterial respiratory activity.

Flexible switch matrix addressable electrode arrays with organic electrochemical transistor and pn diode technology

Due to their effective ionic-to-electronic signal conversion and mechanical flexibility, organic neural implants hold considerable promise for biocompatible neural interfaces. Current approaches are, however, primarily limited to passive electrodes due to a lack of circuit components to realize complex active circuits at the front-end. Here, we introduce a p-n organic electrochemical diode using complementary p- and n-type conducting polymer films embedded in a 15-μm -diameter vertical stack. Leveraging the efficient motion of encapsulated cations inside this polymer stack and the opposite doping mechanisms of the constituent polymers, we demonstrate high current rectification ratios (105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${10}^{5}$$\\end{document}) and fast switching speeds (230 μs). We integrate p-n organic electrochemical diodes with organic electrochemical transistors in the front-end pixel of a recording array. This configuration facilitates the access of organic electrochemical transistor output currents within a large network operating in the same electrolyte, while minimizing crosstalk from neighboring elements due to minimized reverse-biased leakage. Furthermore, we use these devices to fabricate time-division-multiplexed amplifier arrays. Lastly, we show that, when fabricated in a shank format, this technology enables the multiplexing of amplified local field potentials directly in the active recording pixel (26-μm diameter) in a minimally invasive form factor with shank cross-sectional dimensions of only 50×8 μm2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$${\\mu m}^{2}$$\\end{document}.

Synthetic Chemistry and Microelectrode Arrays: Building Stable Platforms for Point of Care Diagnostics

Molecular diagnostics typically require three main components. A molecular interaction that identifies a specific target, a device that detects, quantifies, and records that interaction, and an interface between the two. The interface is critical because it provides a means to fix molecular recognition elements to the surface of the device. For a "point-of-care" application, the interface must be stable both in terms of chemistry and time while still allowing the signal from the molecular interaction to be sensed and recorded by the device. For the use of a microelectrode array as the detection device, construction of the interface must also allow for individual molecular recognition elements to be placed by individual, addressable electrodes in the array.Because of the need for stability and synthetic flexibility, we made the choice to move away from the use of self-assembled monolayers as the interface for developing microelectrode arrays as point-of-care devices. To that end, we have employed diblock copolymers to coat the surface of microelectrode arrays, a change that has offered increased stability of the surface and enabled the use of a broad array of synthetic methods for functionalizing the electrodes in the array. In this talk, we show how the use of a diblock copolymer in conjunction with Cu(I)- and Cu(II)-mediated reactions can be used to functionalize a microelectrode array with multiple DNA-aptamers for the multiplex detection of metabolites. The resulting surface is stable for over 30 weeks (and counting), allows for the detection of multiple metabolites in the same experiment, and retains the detection sensitivity obtained with a self-assembled monolayer.One of the goals of the talk will also be to illustrate for the synthetic community the role that it can play in developing new tools for molecular diagnostics. After all, it is the surface on a microelectrode array that in the long-run defines what an array can be used for and the quality of the resulting analytical experiments. The construction of those surfaces is a synthetic chemistry challenge that moving forward will require both new synthetic methods and new approaches for characterization of the products generated from the new methods. One approach for characterization will be discussed in the context of the Cu(I)- and Cu(II)-mediated reactions employed in the current study.

Electrically Tunable Reflective Metasurfaces with Continuous and Full-Phase Modulation for High-Efficiency Wavefront Control at Visible Frequencies.

All-dielectric optical metasurfaces can locally control the amplitude and phase of light at the nanoscale, enabling arbitrary wavefront shaping. However, lack of postfabrication tunability has limited the true potential of metasurfaces for many applications. Here, we utilize a thin liquid crystal (LC) layer as a tunable medium surrounding the metasurface to achieve a phase-only spatial light modulator (SLM) with high reflection in the visible frequency, exhibiting active and continuous resonance tuning with associated 2π phase control and uncoupled amplitude. Dynamic wavefront shaping is demonstrated by programming 96 individually addressable electrodes with a small pixel pitch of ∼1 μm. The small pixel size is facilitated by the reduced LC thickness, strongly suppressing cross-talk among pixels. This device is used to demonstrate dynamic beam steering with a wide field-of-view and high absolute diffraction efficiencies. We believe that our demonstration may help realize next-generation, high-resolution SLMs, with wide applications in dynamic holography, tunable optics, and light detection and ranging (LiDAR), to mention a few.

Buried graphene heterostructures for electrostatic doping of low-dimensional materials

The fabrication and characterization of steep slope transistor devices based on low-dimensional materials requires precise electrostatic doping profiles with steep spatial gradients in order to maintain maximum control over the channel. In this proof-of-concept study we present a versatile graphene heterostructure platform with three buried individually addressable gate electrodes. The platform is based on a vertical stack of embedded titanium and graphene separated by an intermediate oxide to provide an almost planar surface. We demonstrate the functionality and advantages of the platform by exploring transfer and output characteristics at different temperatures of carbon nanotube field-effect transistors with different electrostatic doping configurations. Furthermore, we back up the concept with finite element simulations to investigate the surface potential. The presented heterostructure is an ideal platform for analysis of electrostatic doping of low-dimensional materials for novel low-power transistor devices.

Nanoparticle-Mediated Signaling for Aptamer-Based Multiplexed Detection of Cortisol and Neuropeptide Y in Serum

Multiplexed profiling of the expression of neurochemical biomarkers of stress, for periodic assessment to enable augmentation of human performance, requires wash-free detection platforms that exhibit reproducible signals from samples in biological matrices. However, alterations in aptamer conformation after binding to targets, such as cortisol, are minimal based on NMR spectra, and the methylene blue signaling is blocked by serum proteins. Hence, in this study, we explore aptamer derivatization with magnetic nanoparticles that are conjugated with multiple methylene blue moieties, to amplify signals and alter the net charge configuration for repulsing serum proteins, so that the aptamer conformation upon target recognition can lead to a signal ON assay in serum media. Based on this, a microchip platform with addressable electrodes that are immobilized with selective aptamer receptors is developed for multiplexed detection of cortisol (1–700 ng/mL) and neuropeptide Y (5–1000 pg/mL) in patient-derived serum samples, which is validated by immunoassays. We envision the application of this sensor for profiling a wider array of human performance biomarkers under stress-related events to develop stress augmentation methodologies.

Programmable High Integration and Resolution Digital Microfluidic Device Driven by Thin Film Transistor Arrays

A digital microfluidic (DMF) system based on electrowetting on dielectrics (EWOD) is a new technology that is able to manipulate microlitre droplets on the plane. Conventional EWOD devices have difficulty achieving high integration and a large number of electrodes due to the limitation of electrical connections. To realize the precise control of multiple droplets in a large-area EWOD device, we propose a programmable high integration and resolution DMF device based on a thin film transistor array (TFTA) &#x2013; EWOD in this paper. The TFTA backplane with thousands of individually addressable electrodes used in electrowetting displays (EWDs) is integrated into this device. A source integrated circuit (IC) and a gate IC are bonded on the substrate glass of the device as the driver chip. A TFTA-EWOD device with <inline-formula> <tex-math notation="LaTeX">$\mathrm {320 \times 240}$ </tex-math></inline-formula> electrodes is designed, fabricated and tested in our experiments. Furthermore, a matching droplet control system with detection and feedback functions was developed and implemented. This system is capable of detecting and analysing individual droplet status while concurrently continuing with other droplet manipulations on the TFTA-EWOD device. The experimental results show that different droplet manipulations, including dispensing, merging and transport, can be carried out successfully on this device. We also successfully applied the proposed device and system to a colorimetric enzymatic assay to show that the proposed scheme is capable of chemical analysis experiments. There are no additional errors introduced by the proposed TFTA-EWOD device. The designed device and matching system proposes a programmable high integration, high resolution, and universal solution for complex DMF applications. We hope that the proposed device and system can provide an experimental platform to other research teams who focus on DMF applications.

Novel pure‐metal tri‐axis CMOS‐MEMS accelerometer design and implementation

This work proposed a pure-metal, single-proof-mass structure fabricated by the standard 0.18 μm one-poly-silicon six-metal (1P6M) CMOS process along with one in-house post-CMOS wet-etching approach. The implemented state-of-the-art symmetrical tri-axis accelerometer consists of the disk-like mezzanine proof-mass and four diagonal double-layered springs. Three sets of the addressable quadrant electrodes underneath the proof-mass with additional interlayer inter-digital comb-conductors help to fulfil the high sensibilities of 248.6, 250.8, and 220.1 mV/G for the x-, y-, and z-axes, respectively. Symmetrical-structure and addressable-electrode design of the device also effectively eliminates the cross-coupling effects. The thin-film composite springs can be width-trimmed for the necessities of specification changes, and the optional calibration pads also provide the on-chip accuracy compensations. The fabricated tri-axis accelerometer reveals stable and consistent results and exemplifies a potential platform design for the highly integrated monolithic CMOS-MEMS system-on-chip applications.

Signaling Studies of Protein-Peptide Binding on Microelectrode Arrays

Electrochemical methods provide unique opportunities for non-traditional synthesis and analytical studies. Using electrochemistry, we are able to synthesize addressable molecular surfaces on microelectrode arrays and then utilize the surface to probe interactions between receptors and their biological targets. To this end, the electrodes on the surface are individually addressable. They can be used as synthetic tools to generate reagents and catalysts and in so doing trigger chemical reactions on the surface of the array above the electrodes. This allows us to synthesize and/or place molecules on the arrays directly above specific individually addressable electrode in the arrays that can then be used to study the binding behavior of those molecules. While this work has shown to be successful, significant challenges still remain. While the binding signals can be observed for peptide – protein interactions on the functionalized surface of the array, the signals obtained are amplified due to avidity effects. This amplification creates difficulties when it comes to comparing the data obtained on an array to the to existing binding data in the literature. At times, it makes it difficult to quantify a binding event at all since the amplification can shift a binding curve to a point where part of it cannot be observed. Therefore, it is extremely important to develop methods by which we can calibrate the signals produced and recorded on the microelectrode arrays and optimize those signals in a reproducible way. For this reason, we have been exploring how the nature of the functionalized array surface influences the binding signal. Our work is exploring how the relative concentration of molecules on the surface of the array can be used tune the value of the binding constant measured for an interaction on a microelectrode array, how the use and length of a linker between the molecule being studied and the array can be used to optimize the intensity of the signal, and how adjusting the hydrophilicity of the functionalized surface can be used to increase the signal to noise associated with the experiments. This work will be discussed along with ways to trouble shoot experiments in connection with surface versus solution issues that can arise.Reference: Nai-Hua Yeh, Yu Zhu, and Kevin D. Moeller*, ChemElectroChem 2019, 6, pp 4134-4143

Building Addressable Libraries: Olefin Functionalization Reactions and the Development of a Site-Selective, Cleavable Linker

Microelectrode arrays are potentially powerful tools for monitoring molecular interactions between small molecules and biological targets in "real-time". Yet while the potential for the arrays is coming into focus, there are still barriers that prevent us from taking full advantage of the devices. Chief among these is the need to construct and characterize molecules on the arrays so that they are specifically located by individually addressable electrodes or groups of electrodes in the array. Currently, we are working on methods to construct larger molecular libraries directly on the arrays, an effort that seeks to avoid transferring the libraries to the array one member at a time. To do so, we need to expand the synthetic toolbox available on the arrays. In that context, olefin functionalization is one of the most powerful strategies in modern organic chemistry because it converts readily available double bonds into a wide array of functional groups. For this reason, we are initially examining the role of cis-dihydroxylation, epoxidation, and diazidation reactions which can play in a site-selective array-based synthesis. The chemistry is already paying dividends. In one application, we have shown that a site-selective cis-hydroxylation reaction can enable a new “safety-catch" linker strategy that is completely orthogonal to the typical deprotection strategies used for diversity of oriented syntheses. The result provides a foundation for future synthetic efforts because it enables full characterization of molecules synthesized by any electrode in an array. In this poster, we will discuss progress towards additional array-based olefin functionalization reactions as well as detail the safety-catch linker strategy mentioned above. Figure 1

Miniaturized probe on polymer SU-8 with array of individually addressable microelectrodes for electrochemical analysis in neural and other biological tissues.

An SU-8 probe with an array of nine, individually addressable gold microband electrodes (100μm long, 4μm wide, separated by 4-μm gaps) was photolithographically fabricated and characterized for detection of low concentrations of chemicals in confined spaces and in vivo studies of biological tissues. The probe's shank (6mm long, 100μm wide, 100μm thick) is flexible, but exhibits sufficient sharpness and rigidity to be inserted into soft tissue. Laser micromachining was used to define probe geometry by spatially revealing the underlying sacrificial aluminum layer, which was thenetched to free the probes from a silicon wafer. Perfusion with fluorescent nanobeads showed that, like a carbon fiber electrode, the probe produced no noticeable damage when inserted into rat brain, in contrast to damage from an inserted microdialysis probe. The individual addressability of the electrodes allows single and multiple electrode activation. Redox cycling is possible, where adjacent electrodes serve as generators (that oxidize or reduce molecules) and collectors (that do the opposite) to amplify signals of small concentrations without background subtraction. Information about electrochemical mechanisms and kinetics may also be obtained. Detection limits for potassium ferricyanide in potassium chloride electrolyte of 2.19, 1.25, and 2.08μM and for dopamine in artificial cerebral spinal fluid of 1.94, 1.08, and 5.66μM for generators alone and for generators and collectors during redox cycling, respectively, were obtained.

Thin-film-transistor digital microfluidics for high value in vitro diagnostics at the point of need.

The latest developments in thin-film-transistor digital-microfluidics (TFT-DMF, also known by the commercial name aQdrop™) are reported, and proof of concept application to molecular diagnostics (e.g. for coronavirus disease, COVID-19) at the point-of-need demonstrated. The TFT-DMF array has 41 thousand independently addressable electrodes that are capable of manipulating large numbers of droplets of any size and shape, along any pathway to perform multiple parallel reactions. Droplets are continually tracked and adjusted through closed-loop feedback enabled by TFT based sensors at each array element. The sample-to-answer molecular in vitro diagnostic (IVD) test for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) includes nucleic acid extractions from saliva, removal of dsDNA and quantitative reverse transcription polymerase chain reaction (RT-PCR). This proof of concept illustrates how the highly configurable TFT-DMF technology can perform many reactions in parallel and thus support the processing of a range of sample types followed by multiple complex multi-step assays.

Flexible and Stretchable Ultrasonic Transducer Array Conformed to Complex Surfaces

In this work, a flexible and stretchable ultrasonic transducer array consisting of 3 × 3 elements is proposed to achieve conformal contact with various nonplanar complex surfaces. The array is formed by integrating rigid piezoelectric ceramics with serpentine hinges in a single-layered configuration and encapsulated by compliant elastomers. The addressable electrodes arrangement allows the use of a small number of connecting wires to excite each element in the array. The developed ultrasonic transducer has a resonant frequency of 1.91 MHz and the initial acoustic characterization is demonstrated. The serpentine electrodes can be stretched up to 33% without failure and the array exhibits excellent flexibility of bending, folding, twisting, and rolling up, indicating its reliable electrical connection and stable mechanical property. Moreover, the performance of the array attached to curved surfaces, human skins, and medical catheters is also demonstrated. The results indicate a convenient and robust method to achieve the preparation of a flexible and stretchable ultrasonic transducer array, which extends conventional rigid ultrasonic transducers to future wearable applications.

Localized and Programmable Chemical Vapor Deposition Using an Electrically Charged and Guided Molecular Flux.

Chemical vapor deposition is a widely used material deposition technique. It commonly provides a uniform material flux to the substrate to cause uniform thin film growth. However, the ability to precisely adjust the local deposition rate would be highly preferable. This communication reports on a chemical vapor deposition method performed in a localized and programmable fashion by introducing an electrically charged and guided molecular flux. This allows for local adjustments of the deposition rate and three-dimensional shape by controlling the electric fields. Specifically, the precursor molecules are charged and then guided by arrays of electrodynamic funnels, which are created by a patterned dielectric layer, to predetermined deposition locations with a minimal spot size of 250 nm. Furthermore, nearest neighbor coupling is reported as a shaping method to cause the deposition of three-dimensional nanostructures. Additionally, the integration of individually addressable domain electrodes offers programmable charge dissipation to achieve an ON/OFF control. The described method is applicable to a wide variety of materials and precursors. Here, the localized and programmable deposition of three-dimensional copper oxide, chromium oxide, zinc oxide, and carbon nanowires is demonstrated.