Highly Stretchable and Wearable Strain Sensor Based on Printable Carbon Nanotube Layers/Polydimethylsiloxane Composites with Adjustable Sensitivity

Abstract

Strain sensors that are capable of monitoring complex human motions with high accuracy are highly desirable for developing wearable electronics. This paper reports the fabrication of highly stretchable and sensitive multidirectional strain sensors with tunable strain gauge factors by employing a digitally controlled printer to incorporate carbon nanotube (CNT) layers into polydimethylsiloxane (PDMS) substrates. The fabricated sensors exhibit a high stretchability (up to 45%) and sensitivity with a gauge factor of 35.75. The gauge factors could be easily modulated by tuning the number of CNT printing cycles to accommodate diverse requirements. The cyclic loading-unloading test results revealed that the composite strain sensors exhibited excellent long-term durability. Particularly, in this work, for the first time, human-motion-induced strain was measured by a motion capture system and compared with the strain data obtained from the fabricated strain sensors. The deviation of strains measured by composite sensors is less than 20%, indicating the great accuracy of CNT/PDMS sensors to quantify the amount of motion-induced strain. Of significant importance is that due to the flexibility of the printing technique used, rosette-type sensors were fabricated to simultaneously measure strains along multiple axes. These superior sensing capabilities of the fabricated CNT/PDMS strain sensors give them great application potential in motion-detecting systems.

Stretchable and calibratable graphene sensors for accurate strain measurement

“…They are commonly used for the development of soft robotics and wearable devices. [1][2][3][4][5][6] To reach high stretchability, fibres 7 and elastomers -Ecoflex rubber, 8,9 polydimethylsiloxane [10][11][12][13][14][15][16] and nature rubber 17 -have been composed with various electrically conductive fillers, including but not limited to metal nanowires, 1,18,19 Pt-coated polymer nanofibers, 20 carbon nanotubes, [21][22][23][24] graphene, 15,25,26 PEDOT:PSS, 27 carbon conductive grease 28 and carbonized silk. 29 The efforts have been focused on pursuing high linearity, 26,30 stretchability, 17,21 sensitivity 7,24,31,32 and cyclic stability, 26,[33][34][35] less hysteresis for resistivesensors 33,36 as well as other environmental properties.…”

Directed and On‐Demand Alignment of Carbon Nanotube: A Review toward 3D Printing of Electronics

“…Till now, CNT‐based wearable sensors have seen many applications in healthcare, motion detection and environmental probing . Among those CNT‐based wearables, 3D printed wearable devices that have been demonstrated are supercapacitor, strain sensor, motion sensor, chemical vapor sensing system, and transistor . In addition, bioactive CNTs ink can be used to fabricate biocompatible 2D or 3D hybrid tissue construct with good electrical property for monitoring application …”

Ultrasensitive embedded sensor for composite joints based on a highly aligned carbon nanotube web

“…The performance comparison shows that the CNT-SLW has excellent electrical resistance response to deformation. This is governed by (i) strong interfacial bonding between CNTs and the adhesive matrix which results in very effective load transfer to the CNTs, harnessing the piezoresistive properties of the CNTs, and (ii) the high degree of alignment of the CNTs within the web, causes significant changes in contact area between CNTs upon crack opening and widening [38][39][40][41][42][43]. In contrast, the CNT-SLW perpendicular to the load direction showed only a ~37 % increase in relative resistance (∆R/R o ) and only close to failure (Inset Fig.…”