Full-field, conformal epiretinal electrode array using hydrogel and polymer hybrid technology

Zhou, Ming; Young, Benjamin K.; Valle, Elena della; Koo, Beomseo; Kim, Dong Ha; Weiland, James D.

doi:10.1038/s41598-023-32976-9

Cited by 3 publications

(1 citation statement)

References 57 publications

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“…Impedance for these PtIr functionalized SPFe at 1 kHz was 1341.4 ± 517.8 kΩ (n=21), which does scale appropriately to its associated surface area when compared to large-blowtorch electrodes (344 ± 16.9 kΩ, n = 70) as noted in previous literature [ 68 ]. While there is a large variability in the capacitance and impedance for these electrodes before coating, the plating step tends to act as a cleaning step [ 69 ] which helps to lower the variability post-coating in both PEDOT:pTS and PtIr cases. Also, the SPFe shape has variablility, which is reflected in the impedance data.…”

Section: Resultsmentioning

confidence: 99%

Fabrication and Validation of Sub-Cellular Carbon Fiber Electrodes

Richie,

Letner,

Mclane-Svoboda

et al. 2024

IEEE Trans. Neural Syst. Rehabil. Eng.

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Multielectrode arrays for interfacing with neurons are of great interest for a wide range of medical applications. However, current electrodes cause damage over time. Ultra small carbon fibers help to address issues but controlling the electrode site geometry is difficult. Here we propose a methodology to create small, pointed fiber electrodes (SPFe). We compare the SPFe to previously made blowtorched fibers in characterization. The SPFe result in small site sizes (105.4 ± 20.8 μ m 2 ) with consistently sharp points (20.8 ± 7.64°). Additionally, these electrodes were able to record and/or stimulate neurons multiple animal models including rat cortex, mouse retina, Aplysia ganglia and octopus axial cord. In rat cortex, these electrodes recorded significantly higher peak amplitudes than the traditional blowtorched fibers. These SPFe may be applicable to a wide range of applications requiring a highly specific interface with individual neurons.

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Section: Resultsmentioning

confidence: 99%

Fabrication and Validation of Sub-Cellular Carbon Fiber Electrodes

Richie,

Letner,

Mclane-Svoboda

et al. 2024

IEEE Trans. Neural Syst. Rehabil. Eng.

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Avoidance of axonal stimulation with sinusoidal epiretinal stimulation

Corna,

Cojocaru,

Bui

et al. 2024

J. Neural Eng.

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Objective. Neuromodulation, particularly electrical stimulation, necessitates high spatial resolution to achieve artificial vision with high acuity. In epiretinal implants, this is hindered by the undesired activation of distal axons. Here we investigate focal and axonal activation of Retinal Ganglion Cells (RGCs) for different sinusoidal stimulation frequencies. Our results can be exploited to define a selective stimulation strategy to avoid axonal activation in retina implants. Approach. RGC responses to epiretinal sinusoidal stimulation at frequencies between 40 and 100 Hz were tested in ex-vivo photoreceptor degenerated (rd10) retina explants. Experiments were conducted using a high-density CMOS-based Micro Electrode Array, which allows to locate RGC cell bodies and axons with high spatial resolution while performing simultaneous recording and stimulation. Main results. We report current and charge density threshold for focal and distal axon activation for sinusoidal stimulation at 40, 60, 80 and 100 Hz, in the order of 0.5 µA. We identify selective stimulation for 40 and 60 Hz up to 0.23 and 0.28 µA (173 and 148 nC/mm2), showing how the selective stimulation window increases when reducing the stimulation frequency. With the use of synaptic blockers, we demonstrate the underlying direct activation mechanism of the ganglion cells. Finally, with the use of high resolution electrical imaging and axon tracking, we investigated the extent of the activation in axonal bundles. Significance. 40 and 60 Hz sinusoidal electrical stimulation can be applied to achieve focal activation of RGCs in epiretinal configuration. The presented results can be implemented as a stimulation strategy to avoid axonal stimulation solving one of the major limitations of artificial vision and retina implants. The results could be extended to other fields of neuroprosthetics to achieve selective focal electrical stimulation.

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The e-Flower: A hydrogel-actuated 3D MEA for brain spheroid electrophysiology

Martinelli,

Akouissi,

Liebi

et al. 2024

Sci. Adv.

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Traditional microelectrode arrays (MEAs) are limited to measuring electrophysiological activity in two dimensions, failing to capture the complexity of three-dimensional (3D) tissues such as neural organoids and spheroids. Here, we introduce a flower-shaped MEA (e-Flower) that can envelop submillimeter brain spheroids following actuation by the sole addition of the cell culture medium. Inspired by soft microgrippers, its actuation mechanism leverages the swelling properties of a polyacrylic acid hydrogel grafted to a polyimide substrate hosting the electrical interconnects. Compatible with standard electrophysiology recording systems, the e-Flower does not require additional equipment or solvents and is ready to use with preformed 3D tissues. We designed an e-Flower achieving a curvature as low as 300 micrometers within minutes, a value tunable by the choice of reswelling media and hydrogel cross-linker concentration. Furthermore, we demonstrate the ability of the e-Flower to detect spontaneous neural activity across the spheroid surface, demonstrating its potential for comprehensive neural signal recording.

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Full-field, conformal epiretinal electrode array using hydrogel and polymer hybrid technology

Cited by 3 publications

References 57 publications

Fabrication and Validation of Sub-Cellular Carbon Fiber Electrodes

Fabrication and Validation of Sub-Cellular Carbon Fiber Electrodes

Avoidance of axonal stimulation with sinusoidal epiretinal stimulation

The e-Flower: A hydrogel-actuated 3D MEA for brain spheroid electrophysiology

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