Abstract
AbstractThiol‐ene/acrylate, a softening polymer material, rapidly gained attention during the past few years as a substrate of intracortical probes, as soft polymers can mitigate foreign body response by reducing mechanical mismatch between the neural implant and the surrounding brain tissue. This paper presents a comprehensive analysis of a thiol‐ene/acrylate based microECoG (micro – electrocorticography, μECoG) device with 31 sputtered iridium oxide electrodes. Long‐term electrochemical measurements provide firm evidence on the reliability of the novel layer structure and the related packaging method. In vivo impedance measurements indicated stable electrode yield (over 75%), without apparent signs of delamination or material degradation over 75 days. Awake recordings of theta oscillations with signal‐to‐noise ratio between 1.04 and 5.74 over this extended period also confirmed the applicability of the device. Chronic immune response characterized by Glial Fibrillary Acidic Protein staining of astrocytes and fluorescent Nissl (NeuroTrace) staining of neurons revealed only modest foreign body reaction after 80 days of implantation. The study presents novel data that confirms the feasibility of softening polymer‐based μECoG devices as chronically implantable neural interfaces.
Highlights
Thiol-ene/acrylate, a softening polymer material, rapidly gained attention tissue
ECoG signals are rich in frequency components that are device with 31 sputtered iridium oxide difficult to record in a reliable manner electrodes
Chronic immune response characterized by Glial Fibrillary Acidic Protein staining of astrocytes and fluorescent Nissl (NeuroTrace) staining of neurons revealed only modest foreign body reaction after 80 days of implantation
Summary
Composition and synthesis of the thiol-ene/acrylate polymer substrate is described in the prior work.[39] The μECoG device is designed to be used with ease in chronic mouse experiments, where challenges of limited space and weight need to be addressed. The final device is shown on Figure 1A. The overall thickness of the device is ≈14 μm in the SMP only regions and ≈18 μm over the traces (see Figure 1C). The microfabrication process, which was carried out at Qualia Labs, Inc., relies on the micromachining scheme of the intracortical probe published earlier.[39] Briefly, a thiol-ene/acrylate based SMP substrate with 2 μm Parylene C encapsulation around the traces was used. Www.advmattechnol.de were conducted in a Faraday-cage. μECoGs, evaluated with EIS, were exclusively used in in vitro experiments
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