Scaling Metal‐Elastomer Composites toward Stretchable Multi‐Helical Conductive Paths for Robust Responsive Wearable Health Devices

Abstract

Stretchable electronics have advanced rapidly and many applications require high repeatability and robustness under various mechanical deformations. It has been described here that how a highly stretchable and reliable conductor composite made from helical copper wires and a soft elastomer, named eHelix, can provide mechanically robust and strain‐insensitive electronic conductivity for wearable devices. The reversibility of the mechanical behavior of the metal‐elastomer system has been studied using finite element modeling methods. Optimal design parameters of such helical metal‐elastomer structures are found. The scaling of multiple copper wires into such helical shapes to form a Multi‐eHelix system is further shown. With the same elastomer volume, Multi‐eHelix has more conductive paths and a higher current density than the single‐eHelix. Integrations of these eHelix stretchable conductors with fabrics showed wearable displays that can survive machine‐washes and hundreds of mechanical loading cycles. The integration of the eHelix developed by us with a wearable optical heart rate sensor enabled a wearable health monitoring system that can display measured heart rates on clothing. Furthermore, Multi‐eHelix conductors are used to connect flexible printed circuit boards and piezoresistive sensors on a tactile sensing glove for the emerging sensorized prosthetics.

Multifunctional fibrous wound dressings for refractory wound healing

“…Recently, flexible electronics based on hydrogel, elastomer, fibrous materials, etc., have drawn tremendous attention in developing wearable healthcare systems, human-machine interactions, on-demand drug delivery, etc. [183][184][185] Among these promising applications based on fibrous material, point-of-care monitoring of infected wounds is significant for medical personnel to manage the wounds effectively and timely, however, is not much explored now. Among the current few studies, Mariani et al fabricated a fully textile device by integrating a sensing layer consisting of a two-terminal pH sensor printed on a textile substrate and an absorbent gauze layer, ensuring the delivery of wound exudates to the sensor area.…”

Lantern‐Inspired On‐Skin Helical Interconnects for Epidermal Electronic Sensors

“…[37,38] In the past, helical structures have been presented in soft electronics and wearable electronics as reliable interconnects of functional devices on elastic substrates or smart clothing. [39][40][41] However, due to these proposed interconnects with helical structure lack of adhesion to the skin, there are few reports on the application of helical interconnects for epidermal electronic sensors.…”

A Hybrid Strategy‐Based Ultra‐Narrow Stretchable Microelectrodes with Cell‐Level Resolution

“…[3,[8][9][10][11][12][13][14][15][16][17][18][19][20] Typically, the width of those stretchable electrodes was usually larger than 100 µm or even in millimeters. [20][21][22][23][24][25][26][27] As a matter of fact, it is not easy to fabricate stretchable ultra-narrow electrodes, like in 10 µm width. [28][29][30] For serpentine structures, the typical width of stretchable electrodes reported is ≈100 µm.…”