Abstract
Bioelectronics stickers that interface the human epidermis and collect electrophysiological data will constitute important tools in the future of healthcare. Rapid progress is enabled by novel fabrication methods for adhesive electronics patches that are soft, stretchable and conform to the human skin. Yet, the ultimate functionality of such systems still depends on rigid components such as silicon chips and the largest rigid component on these systems is usually the battery. In this work, we demonstrate a quickly deployable, untethered, battery-free, ultrathin (~5 μm) passive “electronic tattoo” that interfaces with the human skin for acquisition and transmission of physiological data. We show that the ultrathin film adapts well with the human skin, and allows an excellent signal to noise ratio, better than the gold-standard Ag/AgCl electrodes. To supply the required energy, we rely on a wireless power transfer (WPT) system, using a printed stretchable Ag-In-Ga coil, as well as printed biopotential acquisition electrodes. The tag is interfaced with data acquisition and communication electronics. This constitutes a “data-by-request” system. By approaching the scanning device to the applied tattoo, the patient’s electrophysiological data is read and stored to the caregiver device. The WPT device can provide more than 300 mW of measured power if it is transferred over the skin or 100 mW if it is implanted under the skin. As a case study, we transferred this temporary tattoo to the human skin and interfaced it with an electrocardiogram (ECG) device, which could send the volunteer’s heartbeat rate in real-time via Bluetooth.
Highlights
Surface biopotentials collected from the human epidermis contain important information about human physiology, such as muscular, heart and brain activities
An alternative approach that has been under research is the utilization of wireless power transfer (WPT) to power or charge biomedical devices[18,19,20,21,22,23,24,25]
There has been some research with skin-interfaced bioelectronics powered by WPT, but these usually operate with far-field techniques[7,29,30]
Summary
Surface biopotentials collected from the human epidermis contain important information about human physiology, such as muscular, heart and brain activities. The interest in E-tattoos is mainly because these films are comfortable and nearly imperceptible Applications of these films have been shown in monitoring muscular activity through Electromyography (EMG) to control UAVs12 or prosthetic hands[13], to monitor heart rate through Electrocardiography (ECG)[14,15], for the acquisition of brain signals through Electroencephalography (EEG)[16], and for electrochemical analysis of sweat[17]. As the conducting material for the tattoo circuits, the application of printed conductive polymers such as PEDOT: PSS (poly(3,4-ethylenedioxythiophene) polystyrene sulfonate)[13], and screen printed carbon based conductors[10] are promising for skin-interfacing electrodes They are not a good option for energy harvesting due to their low electrical conductivity. Various types of conductive composites were developed using different blends of elastic polymers and conductive micro/nanoparticles, nanowires, or nanotubes[36,37,38], for stretchable electronics, but conductive composites typically suffer from the “Mullin’s effect”[39] and degradation of the percolating network when stretched
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