High-Performance Flexible Microneedle Array as a Low-Impedance Surface Biopotential Dry Electrode for Wearable Electrophysiological Recording and Polysomnography

Abstract

Highlights Polyimide-based flexible microneedle array (PI-MNA) electrodes realize high electrical/mechanical performance and are compatible with wearable wireless recording systems. The normalized electrode–skin interface impedance (EII) of the PI-MNA electrodes reaches 0.98 kΩ cm2 at 1 kHz and 1.50 kΩ cm2 at 10 Hz, approximately 1/250 of clinical standard electrodes. This is the first report on the clinical study of microneedle electrodes. The PI-MNA electrodes are applied to clinical long-term continuous monitoring for polysomnography. Abstract Microneedle array (MNA) electrodes are an effective solution to achieve high-quality surface biopotential recording without the coordination of conductive gel and are thus very suitable for long-term wearable applications. Existing schemes are limited by flexibility, biosafety, and manufacturing costs, which create large barriers for wider applications. Here, we present a novel flexible MNA electrode that can simultaneously achieve flexibility of the substrate to fit a curved body surface, robustness of microneedles to penetrate the skin without fracture, and a simplified process to allow mass production. The compatibility with wearable wireless systems and the short preparation time of the electrodes significantly improves the comfort and convenience of electrophysiological recording. The normalized electrode–skin contact impedance reaches 0.98 kΩ cm2 at 1 kHz and 1.50 kΩ cm2 at 10 Hz, a record low value compared to previous reports and approximately 1/250 of the standard electrodes. The morphology, biosafety, and electrical/mechanical properties are fully characterized, and wearable recordings with a high signal-to-noise ratio and low motion artifacts are realized. The first reported clinical study of microneedle electrodes for surface electrophysiological monitoring was conducted in tens of healthy and sleep-disordered subjects with 44 nights of recording (over 8 h per night), providing substantial evidence that the electrodes can be leveraged to substitute for clinical standard electrodes.

Recent Progress in Long-Term Sleep Monitoring Technology

“…Reproduced under the terms of the CC-BY Creative Commons Attribution License, Copyright 2022 American Chemical Society. ( d ) Microneedle array electrodes on a flexible substrate [ 102 ]. Reproduced under Creative Commons Attribution 4.0 International License, Copyright 2022 by the authors, published by Shanghai Jiao Tong University Press.…”

Skin preparation–free, stretchable microneedle adhesive patches for reliable electrophysiological sensing and exoskeleton robot control

“…The reliable and accurate recording of electrophysiological (EP) signals from the skin is crucial for clinical diagnoses (1)(2)(3)(4), rehabilitation (5,6), and human-machine interfaces (HMIs) (7)(8)(9). Preparation-free EP sensors with superior recording quality over extended periods regardless of skin conditions are vital and will bring practical impact on a wide variety of real-world wearable applications (10)(11)(12)(13). Conventionally, clinical metal electrodes with conductive gel or electrodes with hydrogel are commonly used for EP sensing owing to their satisfactory signal acquisition performance and cost-effectiveness (14,15).…”

“…Advancements in materials and microfabrication techniques have attempted to overcome these limitations by developing soft and dry epidermal electrodes that offer comfortable long-term EP signal monitoring without the need for electrolyte gel (2,3,7,8,11,(22)(23)(24)(25)(26)(27). Nevertheless, without skin preparation such as cleaning and exfoliation, these dry electrodes attached to the skin surface typically exhibit high and unstable skin contact impedance due to factors such as hair, the stratum corneum, and skin secretions (28).…”

Prediction of drug permeation through microneedled skin by machine learning

“…A microneedle (MN) patch consists of an array of MNs of a few hundred microns in length, made of biocompatible materials, such as metals or polymers 1 . These MNs can enhance drug permeation into the skin and/or main circulation, by creating multiple micron‐sized passages through skin, a formidable biological barrier preventing external substances from entering human body 2–5 . Owing to the simple concept of MN and technological feasibility of MN fabrication, MN has been extensively studied as a device to deliver into human a variety of therapeutic agents, for example, small‐molecule compounds, 6,7 peptides, 8–10 mRNA, 11 proteins, 12 and extracellular vesicles 13 …”