Graded Microstructured Flexible Pressure Sensors with High Sensitivity and an Ultrabroad Pressure Range for Epidermal Pulse Monitoring

Precisely
detecting epidermal pulse waves with pressure sensors
is crucial for pulse-based personalized health-monitoring technologies.
However, developing a pressure sensor that simultaneously demonstrates
high sensitivity and an ultrabroad pressure range and a convenient
fabrication process for large-scale production is a considerable challenge.
Herein, by utilizing a commercial conductive fabric (CF) and a silica
gel film, we develop a high-performance pressure sensor (HPPS) for
the monitoring of human physiological signals. Based on convenient
turnover formwork technology, the silica gel film was fabricated by
replicating the microstructure of the sandpaper surface. This microstructure
and the plain weave structure on the CF surface together provide a
sharp increase in the contact-separation area and structural compressibility,
which are beneficial for the enhancement of output performance. Made
of these two materials, the graded microstructured HPPS holds high
sensitivity (4.5 mV/Pa), an ultrabroad pressure range (0–30
kPa), a wide working frequency bandwidth (up to 35 Hz), decent stability
(>50,000 cycles), and a simple fabrication process that is suitable
for large-scale production. Given these noticeable features, the developed
HPPS not only succeeds in precisely detecting subtle pulse waves on
various positions of different people but can also objectively capture
changes in cardiovascular parameters caused by exercise training at
different intensities in real time. These findings exhibit the enormous
potential application of HPPS in tracking an individual’s health
status and comprehensively evaluating exercise intensity.