Abstract
In this paper, a flexible Ag/CNTs-PDMS (polydimethylsi-loxane) composite film sensor based on the novel design philosophy was prepared. Its force-electric effect mechanism is based on the generation of micro-cracks in the Ag film during external forcing, leading to resistance variation. Experimental results find that Ag film thickness has a strong influence on the sensor’s sensitivity, which exhibits a tendency of first increasing and then decreasing the Ag film thickness, and also has an optimal thickness of 4.9 μm for the maximum sensitivity around 30. The sensitive mechanism can be theoretically explained by using the quantum tunneling effect. Due to the use of the wrinkled carbon nanotubes (CNTs) film, this sensor has advantages, such as high sensitivity, large strain range, good stability and durability, cheap price, and suitability for large-scale production. Preliminary applications on human-body monitoring reveal that the sensor can detect weak tremors and breathe depth and rate, and the corresponding heartbeat response. It provides possibilities to diagnose early Parkinson’s disease and exploit an early warning system for sudden infant death syndrome and sleep apnea in adults. In addition, as a force-electric effect sensor, it is expected to have broad application areas, such as a man-machine cooperation, and a robotic system.
Highlights
Monitoring human physiological signals is regarded as an effective method for disease diagnosis and health assessment [1]
Schwartz et al [16] prepared a flexible polymer transistor with high pressure sensitivity for application in electronic skin and health monitoring. They demonstrated that this sensor could be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which might lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine
Ag NP ink and carbon nanotubes (CNTs) paste were mixed with tunable component concentrations, and the composite mixture was patterned onto a polydimethylsiloxane (PDMS) substrate of desired shape and geometry by either painting or printing
Summary
Monitoring human physiological signals is regarded as an effective method for disease diagnosis and health assessment [1]. The wearable and flexible medical sensor has attracted much attention in the prospect of monitoring the general well-being of interested users, the real-time performance of athletes, or the disease status of patients [2,3] The use of this device encourages people to take a greater interest in their own healthcare in a more convenient and cheaper way and improves their compliance. Lee et al [23] firstly developed highly-sensitive, transparent, and durable pressure sensors based on sea-urchin-shaped metal nanoparticles (Au, Ag) This device could detect minute movements of human muscles, such as finger bending and hand motion. Ag NP (silver nanoparticles) ink and CNTs paste were mixed with tunable component concentrations, and the composite mixture was patterned onto a polydimethylsiloxane (PDMS) substrate of desired shape and geometry by either painting or printing This electronic whisker could detect minute pressure changes and its properties remained almost unchanged for 1000 cycles. By using this sensor, we continued preliminary monitoring of the human body signals, including subtle human motions, heartbeat, and breathing, which exhibited wide potential applications in the prophylactic medicine field, such as early diagnosis of Parkinson’s disease, monitoring and prevention of sudden infant death syndrome and sleep apnea in adults
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