Highly Stretchable and Wearable Graphene Strain Sensors with Controllable Sensitivity for Human Motion Monitoring

Abstract

Because of their outstanding electrical and mechanical properties, graphene strain sensors have attracted extensive attention for electronic applications in virtual reality, robotics, medical diagnostics, and healthcare. Although several strain sensors based on graphene have been reported, the stretchability and sensitivity of these sensors remain limited, and also there is a pressing need to develop a practical fabrication process. This paper reports the fabrication and characterization of new types of graphene strain sensors based on stretchable yarns. Highly stretchable, sensitive, and wearable sensors are realized by a layer-by-layer assembly method that is simple, low-cost, scalable, and solution-processable. Because of the yarn structures, these sensors exhibit high stretchability (up to 150%) and versatility, and can detect both large- and small-scale human motions. For this study, wearable electronics are fabricated with implanted sensors that can monitor diverse human motions, including joint movement, phonation, swallowing, and breathing.

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.…”

“…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.…”

“…[18,[33][34][35] To fabricate the wearable sensors, conventional lithographic processes can be extended to pattern nanomaterials. [23,[36][37][38] Solution based processing methods such as spray coating, [25,39,40] drop casting, [41][42][43][44][45] spin coating, [46,47] dip coating, [48] vacuum filtration, [49][50][51] and layer-by-layer assembly [52] were commonly used for fabrication of nanomaterial-based sensors. Direct spinning of CNTs onto a substrate or into yarns [53][54][55] and electrospinning of nanofibers or NWs were reported to produce fiber-like nanomaterials.…”

Wearable Flexible Sensors: A Review

“…Strain sensors [125][126][127] are the most important category of flexible sensors which have been used for multiple disciplinary applications. Human motion detection [66,128], forces and acoustic vibrations [31], artificial skins [129] are some of the other applications for those sensors. Flexible sensors have been widely used as pressure sensors [21,31,130] due to their high flexibility and bendability depending on the raw material used for its fabrication.…”