Addressable Electrode Array Research Articles

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}.

Local hydrogel fabrication based on electrodeposition with a large-scale integration (LSI)-based amperometric device

Addressable electrode arrays are widely used in a number of applications, such as electrochemical imaging and high-throughput assays. Recently, large-scale integration (LSI) technologies have been used to prepare electrochemical devices containing signal amplifiers and switching elements, such that multiple highly sensitive sensors can be incorporated into these devices. Because these devices induce chemical reactions at the target electrodes, biomaterials such as hydrogels can be electrochemically fabricated. In this study, we present a new biofabrication strategy using the electrochemical device. We used an LSI device to locally electrodeposit chitosan hydrogels at the target electrodes, with the goal of fabricating the designed hydrogels. The hydrogels were fabricated via the generation of Cl2 at the anodes where a potential of 0.95 V was applied. The biofabrication method was utilized for three bioapplications. First, three-dimensionally designed chitosan hydrogels, for example apple-shaped and layered hydrogels were fabricated on this device by electrodepositing them for 10–30 s. In order to demonstrate biosensing, glucose oxidase and horseradish peroxidase were modified at the target electrodes through hydrogel electrodeposition; consequently, droplets containing glucose and H2O2 were electrochemically imaged at the same time using the electrochemicolor imaging technique we developed. Since this system can be used to fabricate hydrogels containing enzymes only at the target sensors, glucose and H2O2 were separately monitored. The detection limit of glucose was less than 0.5 mM. In addition, the chitosan hydrogels were electrodeposited only in the target areas such that cells only adhering at unmodified areas, resulting in cell patterning. We show that the LSI device is useful for the fabrication of local hydrogels for several bioapplications such as biosensing and cell culturing.

Electrochemical Activation of the Tetrazine Ligation for Surface Modification

Our lab has been interested in developing conjugation reactions that can be triggered by electrochemical potential. Such reactions could have application in the functionalization of independently addressable electrode arrays. These include past effortsusing the electrochemistry to locally generate copper+1 to trigger the well-known copper catalyzed azide alkyne cycloaddition. Our lab has been interested in an alternative bioorthogonal reaction, the tetrazzini ligation, as a versatile coupling tool. Unlike “click” chemistry, the tetrazine ligation does not have a redox active catalyst. However, one of the reactive components (the tetrazine) is redox active and can be reduced to a dihydrotetrazine, preventing cycloaddition. Through this manner, bioconjugation can be controlled electrochemically. I will summarize our findings in this area and discuss applications.

DNA multi-bit non-volatile memory and bit-shifting operations using addressable electrode arrays and electric field-induced hybridization

DNA has been employed to either store digital information or to perform parallel molecular computing. Relatively unexplored is the ability to combine DNA-based memory and logical operations in a single platform. Here, we show a DNA tri-level cell non-volatile memory system capable of parallel random-access writing of memory and bit shifting operations. A microchip with an array of individually addressable electrodes was employed to enable random access of the memory cells using electric fields. Three segments on a DNA template molecule were used to encode three data bits. Rapid writing of data bits was enabled by electric field-induced hybridization of fluorescently labeled complementary probes and the data bits were read by fluorescence imaging. We demonstrated the rapid parallel writing and reading of 8 (23) combinations of 3-bit memory data and bit shifting operations by electric field-induced strand displacement. Our system may find potential applications in DNA-based memory and computations.

A disposable paper-based electrochemical sensor with an addressable electrode array for cancer screening

A novel addressable electrode array based on paper was assembled on the crossing points of the row/column electrodes to form a 4 × 6 sensor array by a facile home-made device-holder, one paper layer contained the sensing sites, the other paper layer the printed counter electrode and reference electrode.

Individually addressable electrode array for multianalyte electrochemiluminescent immunoassay based on a sequential triggering strategy

Multianalyte immunoassay in a single run is often necessary to monitor or quantitate several components in a complex sample matrix for various purposes. In this paper we present a novel, individually addressable electrode array for sequential electrochemiluminescent (ECL) immunoassay using a non-array detector. An immunosensor array was fabricated by site-selectively immobilizing multiple antigens on different electrodes. With a competitive immunoassay format, the amounts of the bound Ru(bpy)(3)(2+) derivative labeled antibodies decreased with the increase of the antigens in the sample, and the ECL signals from different immunosensors were collected in turn by a photomultiplier with the aid of a home-made single-pore-three-throw switch. Using human IgG and rat IgG as model analytes, this multianalyte immunoassay showed detection limits down to 8.9 and 7.2 ng mL(-1) for them, respectively. The results for real sample analysis demonstrated that this strategy can provide a simple, sensitive, low-cost and high-throughput ECL immunosensor array for clinical diagnosis.

Addressable electrode array device with IDA electrodes for high-throughput detection

An electrochemical device is proposed for high-throughput electrochemical detection that consists of 32 row and 32 column electrodes on a single glass substrate. The row and column electrodes are connected to interdigitated array (IDA) electrodes to form 1024 (32 × 32) addressable sensor points in the device. Electrochemical responses from each of the 1024 sensors were successfully acquired on the device within 1 min using redox cycling at individual IDA electrodes, which ensures application of the device to comprehensive, high-throughput electrochemical detection for enzyme-linked immunosorbent assay (ELISA), reporter gene assay for monitoring gene expressions, and DNA analysis.

Microfluid Ejection Device Based on Complementary Metal–Oxide–Semiconductor Technology as an Artificial Synapse

A complementary metal–oxide–semiconductor (CMOS)-based multisite microfluid ejection device was fabricated and demonstrated. An array of microreservoir cells integrated with micropumps was fabricated on this device. Microfluid ejection is based on the actuation of a silicone membrane between the microreservoir and the micropump cell. This membrane was actuated by the gas produced during the electrolysis of water. The device was equipped with a CMOS chip as an addressable electrode array for multisite microfluid ejection. The microfluid ejection cell array was configured on the CMOS chip to realize addressable microfluid ejection. We measured the membrane displacement to characterize the performance of the micropump, and successfully demonstrated microfluid ejection. The volume of the ejected microfluid was nearly proportional to injected charge. These results suggest that the proposed microfluid ejection device is a promising platform for artificial synaptic devices for various scientific and clinical applications.

Dual-side and three-dimensional microelectrode arrays fabricated from ultra-thin silicon substrates

A method for fabricating planar implantable microelectrode arrays was demonstrated using a process that relied on ultra-thin silicon substrates, which ranged in thickness from 25 to 50 µm. The challenge of handling these fragile materials was met via a temporary substrate support mechanism. In order to compensate for putative electrical shielding of extracellular neuronal fields, separately addressable electrode arrays were defined on each side of the silicon device. Deep reactive ion etching was employed to create sharp implantable shafts with lengths of up to 5 mm. The devices were flip-chip bonded onto printed circuit boards (PCBs) by means of an anisotropic conductive adhesive film. This scalable assembly technique enabled three-dimensional (3D) integration through formation of stacks of multiple silicon and PCB layers. Simulations and measurements of microelectrode noise appear to suggest that low impedance surfaces, which could be formed by electrodeposition of gold or other materials, are required to ensure an optimal signal-to-noise ratio as well a low level of interchannel crosstalk.

Electrochemically Generated Acid and Its Containment to 100 Micron Reaction Areas for the Production of DNA Microarrays

An addressable electrode array was used for the production of acid at sufficient concentration to allow deprotection of the dimethoxytrityl (DMT) protecting group from an overlaying substrate bound to a porous reaction layer. Containment of the generated acid to an active electrode of 100 micron diameter was achieved by the presence of an organic base. This procedure was then used for the production of a DNA array, in which synthesis was directed by the electrochemical removal of the DMT group during synthesis. The product array was found to have a detection sensitivity to as low as 0.5 pM DNA in a complex background sample.

Collection, focusing, and metering of DNA in microchannels using addressable electrode arrays for portable low-power bioanalysis.

Although advances in microfluidic technology have enabled increasingly sophisticated biosensing and bioassay operations to be performed at the microscale, many of these applications employ such small amounts of charged biomolecules (DNA, proteins, and peptides) that they must first be preconcentrated to a detectable level. Efficient strategies for precisely handling minute quantities of biomolecules in microchannel geometries are critically needed; however, it has proven challenging to achieve simultaneous concentration, focusing, and metering capabilities with current-generation sample-injection technology. By using microfluidic chips incorporating arrays of individually addressable microfabricated electrodes, we demonstrate that DNA can be sequentially concentrated, focused into a narrow zone, metered, and injected into an analysis channel. This technique transports charged biomolecules between active electrodes upon application of a small potential difference (1 V) and is capable of achieving orders of magnitude concentration increases within a small device footprint. The collected samples are highly focused, with sample zone size and shape defined solely by electrode geometry.

Modeling and Simulation of Electrified Droplets and Its Application to Computer-Aided Design of Digital Microfluidics

Digital microfluidics is the second-generation lab-on-a-chip architecture based upon micromanipulation of droplets via a programmed external electric field by an individually addressable electrode array. Dielectrophoresis (DEP) and electrowetting-on-dielectric (EWOD) are of dominant operating principles. The microfluidic mechanics of manipulating electrified droplets are complex and not entirely understood. This paper presents a numerical simulation method based on droplet electrohydrodynamics. First, a systematic validation study is shown comparing the simulation solution with both analytical and experimental data, quantitatively and qualitatively, and in both steady state and transient time sequences. Such comparison exhibits excellent agreement. Simulations are then used to illustrate its application to computer-aided design of both EWOD-driven and DEP-driven digital microfluidics.

The Removal of the t-BOC Group by Electrochemically Generated Acid and Use of an Addressable Electrode Array for Peptide Synthesis

The Removal of the <i>t</i>-BOC Group by Electrochemically Generated Acid and Use of an Addressable Electrode Array for Peptide Synthesis