Highly Sensitive, Wearable, Durable Strain Sensors and Stretchable Conductors Using Graphene/Silicon Rubber Composites

Abstract

Stretchable, wearable and highly sensitive strain sensors are vital to the development of health monitoring systems, smart robots and human machine interfaces. The recent sensor fabrication progress is respectable, but it is limited by complexity, low sensitivity and short service life. Herein we present a facile, cost-effective and scalable method for the development of high-performance composite strain sensors and stretchable conductors based on a composite film consisting of graphene platelets (GnPs) and silicon rubber. Through calculation by the tunnelling theory using experimental data, the composite film has demonstrated ideal linear and reproducible sensitivity to tensile strains, which was contributed by the superior piezoresistivity of GnPs having tunable gauge factors 27.7 -164.5. The composite sensors fabricated in different days demonstrated pretty similar performance, enabling the application as a health-monitoring device to detect various human motions from finger bending to pulse. They can be used as an electronic skin, a vibration sensor, and a human-machine interface controller. Stretchable conductors were made by coating and encapsulating GnPs with polydimethyl siloxane to create a composite; this structure allows the conductor to be readily bent and stretched with sufficient mechanical robustness and cyclability.

Nanomaterial‐Enabled Wearable Sensors for Healthcare

“…The opening and propagation of cracks www.advancedsciencenews.com www.advhealthmat.de leads to increase in the resistance and on the contrary, the closing of the cracks leads to recovery of the resistance. Examples include strain sensors based on AgNPs coated fiber mat, [56] AuNW/latex, [44,68] CNT/PDMS, [121] CNT-Ecoflex, [39] SWCNT paper-PDMS, [122] graphene/PDMS, [123] graphene woven fabric/ PDMS, [103,124] graphene coated yarns, [52] fragmentized graphene foam/PDMS, [125] and fish-scale-like rGO. [126] Figure 4b shows the fractured SWCNT film attached onto PDMS.…”

“…[170] Copyright 2016, Nature Publishing Group. the strain or pressure induced by radial artery waves at the wrist or finger tip, [44,57,59,103,120,123,126,139,203] jugular venous pulses at the neck [57,59,151] or ankle brachial artery pulses near the foot. [21] Monitoring of respiration rate is critical in diagnosis of many disorders or diseases such as sleep disorders, asthma and anemia.…”

“…Wearable strain sensors with a large strain detection range are widely used to monitor body motions, including finger bending, [41,52,120,123,126] forearm muscle movements, [21,44,52,103,120,123,153] and knee motions. [41,121,153] Figure 10a highlights a CNT based strain sensor used for detection of various knee motions during extending, flexing, marching, squatting, and jumping.…”

“…[121] Both intensity and frequency of the motions can be identified. The phonation vibrations and voice patterns can be monitored using a strain sensor [44,52,103,120,121,123,126] or a pressure sensor [57,141] attached to the neck. An example using a carbonized silk nanofiber based pressure sensor is given in Figure 10b.…”

“…An example using a carbonized silk nanofiber based pressure sensor is given in Figure 10b. [57] Recognizing emotional expressions such as laughing, [46] crying, [46] blinking eyes, [46,103] and others [44,46,103,123] has been realized by using strain sensors to monitor the associated skin movements. Figure 10c shows the skin movements on the forehead and near the mouth during laughing and crying as examples.…”