Sensitivity and strain range are
two mutually exclusive features
of strain sensors, where a significant improvement in flexibility
is usually accompanied by a reduction in sensitivity. The skin of
a human fingertip, due to its undulating fingerprint pattern, can
easily detect environmental signals and enhances sensitivity without
losing elasticity. Inspired by this characteristic, laser-induced
graphene (LIG) with a fingerprint structure is prepared in one step
on a polyimide (PI) film and transferred into an Ecoflex substrate
to assemble resistive strain sensors. Experimentally, the fingerprint-inspired
strain sensor exhibits a superfast response time (∼70 ms),
balanced sensitivity and strain range (a gauge factor of 191.55 in
the 42–50% strain range), and good reliability (>1500 cycles).
Self-organized microcracks, initiated in weak mechanical areas, cause
prominent resistance changes during reconnection/disconnection but
irreversibly fail after excessive stretching. The robust function
of fingerprint-inspired sensors is further demonstrated by real-time
monitoring of tiny pulses, large body movements, gestures, and voice
recognition.
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