Highly sensitive and stretchable strain sensors based on chopped carbon fibers sandwiched between silicone rubber layers for human motion detections

Abstract

Tuning the electromechanical performance in piezoresistive composite strain sensors is primarily attained through appropriately employing the materials system and the fabrication process. High sensitivity along with flexibility in the strain sensing devices needs to be met according to the application (e.g. human motion detection, health and sports monitoring). In this paper, a highly stretchable and sensitive strain sensor with a low-cost fabrication is proposed which is acquired by embedding the chopped carbon fibers sandwiched in between silicone rubber layers. The electrical and mechanical features of the sensor were characterized through stretch/release loading tests where a considerably high sensitivity (the gauge factor about 100) was observed with very low hysteresis. This implies high strain reversibility (i.e. full recovery in each cycle) over 700 loading cycles. Moreover, the sensors exhibited ultra-high stretchability (up to ∼300% elongation) in addition to a low stiffness meaning minimal mechanical effects induced by the sensor for sensitive human motion monitoring applications including large and small deformations. The results suggest the promising capability of the present sensor in reflecting the human body motion detection.

Prospective RFID Sensors for the IoT Healthcare System

“…Some common types of electrochemical sensing include monitoring glucose [14][15][16][17][18][19] and pH [24][25][26]. Carbon nanotubes [50,51] have been developed as glucose and pH sensors because of their curved sidewalls and hydrophobicity that provides strong interactions through π-bonds. Another type of electrochemical sensing is the monitoring of cholesterol [52,53], which is based on the principle of a kind of grease on the membrane of animal cells.…”

Wearable Sensors for Monitoring Human Motion: A Review on Mechanisms, Materials, and Challenges

“…20,24,26 A conventional and still popular method of fabricating piezoresistive sensors is using the composition of a stretchable rubber with conductive materials (such as carbon nanotubes [CNTs], graphene, silver nanowires [AgNWs], and intrinsically conductive polymers [ICPs]). 27–30 Under tensile stress, conductive pathways available inside the material will change direction because of the decreased percolation routes caused by disconnections and the change in the compatibility between the conductive materials and the matrix. Based on this explanation, different transduction mechanisms have been suggested in the literature, such as structure geometry variation, change in the resistivity of the conductive materials (intrinsic piezoresistive effect), a tunneling effect after initial separation between conductive elements, and microcrack propagation, the details of which can be found in other references 20,24 and are out of the scope of this article.…”

“…45,46 The common strategy to enhance tactile sensitivity in this type of sensors is to fabricate patterned microstructures such as pyramids, micropillars, or interlocking hemispheres on the surface, which leads to changes in contact resistance upon the application of varying pressure. 45–48 However, in monitoring human activity, which is the scope of this paper, we deal with medium pressures (10–100 kPa), such as in pulse detection, and high pressures (>100 kPa), such as in large-scale body movements or posture detection. Thus, developing a sensor with the capability to detect a wide range of pressures is of great importance.…”

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“…They have been widely studied and applied in aerospace industry, marine structure design, seismic building construction, and sensor detection. [ 1–6 ] In the face of complex and harsh environment, the theoretical research on the dynamic performance and dynamic stability of composite materials under dynamic load is becoming more and more in‐depth. [ 7–10 ] Due to many complex external loads, the composite structure will produce large vibration and noise problems, which will bring security risks such as performance stability to the structure and equipment.…”