posted on 2020-06-10, 15:43authored byZhenhua Tang, Shuhai Jia, Chenghao Zhou, Bo Li
Piezoresistive
composite-based flexible pressure sensors often
suffer from a trade-off between the sensitivity and measurement range.
Moreover, the sensitivity or measurement range is theoretically limited
owing to the negative piezoresistive coefficient, resulting in resistance
variation below 100%. Here, flexible pressure sensors were fabricated
using the three-dimensional (3D) printing technique to improve both
the sensitivity and sensing range through the positive piezoresistive
effect. With the addition of carbon nanotubes (CNTs) and fumed silica
nanoparticles (SiNPs) as a conductive filler and rheology modifier,
respectively, the viscoelastic silicone rubber solution converted
to a printable gel ink. Soft and porous composites (SPCs) were then
directly printed in air at room temperature. The sensitivity and sensing
range of the SPC-based pressure sensor can be simultaneously tuned
by adjusting the conducting CNT and insulating SiNP contents. By optimizing
the density of the CNT conductive network in the matrix, positive
piezoresistive sensitivity (+0.096 kPa–1) and a
large linear sensing range (0–175 kPa) were obtained. To demonstrate
potential applications, the completely soft SPC-based sensor was successfully
used in grasp sensing and gait monitoring systems. The 3D printed
sensors were also assembled as a smart artificial sensory array to
map the pressure distribution.