Compressible and Stretchable Magnetoelectric Sensors Based on Liquid Metals for Highly Sensitive, Self-Powered Respiratory Monitoring

Abstract

Healthcare monitoring, especially for respiration, has attracted tremendous attention from academics considering the great significance of health information feedback. The respiratory rate, as a critical health indicator, has been used to screen and evaluate potential illness risks in early medical diagnoses. A selfpowered sensing system for medical monitoring is critical and imperative due to needless battery replacement and simple assembly. However, the development of a self-powered respiratory sensor with highly sensitive performance is still a daunting challenge. In this work, a compressible and stretchable magnetoelectric sensor (CSMS) with an arch-shaped air gap is reported, enabling self-powered respiratory monitoring driven by exhaled/inhaled breath. The CSMS contains two key functional materials: liquid metals and magnetic powders both with low Young's modulus, allowing for sensing compressibility and stretchability simultaneously. More importantly, such a magnetoelectric sensor exhibits mechanoelectrical converting capacity under an external force, which has been verified by Maxwell numerical simulation. Owing to the air-layer introduction, the magnetoelectric sensors achieve high sensitivity (up to 17.73 kPa −1 ), fast response, and long-term stability. The highly sensitive and self-powered magnetoelectric sensor can be further applied as a noninvasive, miniaturized, and portable respiratory monitoring system with the aim of warning for potential health risks. We anticipate that this technique will create an avenue for self-powered respiratory monitoring fields.

Emerging Liquid Metal Biomaterials: From Design to Application

“…[96] On this basis, LMs can be widely used in biosensors as interconnects and sensors. [46,[97][98][99]…”

“…While the output signals are usually electrical, such as electricity, resistance, and capacitances. By monitoring the change of output signals, the physiological signals such as biomechanical movements, [76,120,129,130] electrocardiograph (ECG), [105,117,120,124,131] temperatures, [114,121] breaths, [78,97] and contents of some chemicals [78,79,126,131] of human body can be detected.…”

Recent Advances in Multiresponsive Flexible Sensors towards E‐skin: A Delicate Design for Versatile Sensing

“…Interestingly, as the expansion of sensing materials and mechanisms, the changes in magnetic property of magnetic particles upon external stimuli could be used to fabricate magnetic effect-based flexible sensors (Figure 2). [131,132] For example, the change of magnetic flux arising from external mechanical stimulus enables the generation of electrodynamic potential via Faraday's laws of induction, thus creating flexible magnetoelectric sensors. [132] Besides, the magneto-resistive response is also reported in magnetic polymer nanocomposites with electrically conductive nanofillers above its electrical percolation threshold.…”

“…[131,132] For example, the change of magnetic flux arising from external mechanical stimulus enables the generation of electrodynamic potential via Faraday's laws of induction, thus creating flexible magnetoelectric sensors. [132] Besides, the magneto-resistive response is also reported in magnetic polymer nanocomposites with electrically conductive nanofillers above its electrical percolation threshold. [133] However, optical and magnetic effects-based sensing mechanisms are seldom chosen in current flexible and wearable multifunctional sensor design because of the stringent requirement of material traits, complex structural design and inconvenience of signal capture by portable detection apparatuses.…”

“…[39,271] In theory, external stimulations including pressure, temperature and moisture are not only stimulating signals for sensing, but also important drive for electric power generation. Power generation in flexible devices chiefly depends on triboelectric, [272,273] electrostatic, [11] thermoelectric, magnetoelectric, [132] pyroelectric or piezoelectric effects-based nanogenerator, [84,160,273] and also drives from moisture gradient. [31,198,234] Besides, incorporation of flexible supercapacitor, [67] solar cell, [35] or battery [274] is another competent method to provide sufficient working energy without flexibility deterioration.…”