A concise and economical way to build nanoparticle thin-film strain sensors of high gauge factors on a flexible polydimethylsiloxane substrate is developed. The gauge factors for resistance change and capacitance change are much larger than those of many other competing sensors. The small bulk modulus of the substrate provides the sensor a large responsivity for pressure with a frequency bandwidth of kHz. It can be used for tactile sensing that is capable of monitoring human pulse for pre-clinical diagnosis, by resolving minor structures such as peaks of dicrotic pulse and before dicrotic pulse in the waveforms.

In this study, highly-sensitive piezoresistive strain sensors based on gold nanoparticle thin films deposited on a stretchable PDMS substrate by centrifugation were developed to measure arterial pulse waveform. By controlling carbon chain length of surfactants, pH value and particle density of the colloidal solutions, the gauge factors of nanoparticle thin film sensors can be optimized up to 677 in tensile mode and 338 in compressive mode, and the pressure sensitivity up to 350. Low pH and thin nanoparticle films produce positive influences to superior gauge factors. It has been demonstrated that nanoparticle thin film sensors on PDMS substrates were successfully applied to sense arterial pulses in different body positions, including wrist, elbow crease, neck, and chest.