Metal thin films on soft polymers provide a unique opportunity
for resistance-based strain sensors. A mechanical mismatch between
the conductive film and the flexible substrate causes cracks to open
and close, changing the electrical resistance as a function of strain.
However, the very randomness of the formation, shape, length, orientation,
and distance between adjacent cracks limits the sensing range as well
as repeatability. Herein, we present a breakthrough: the Zerogap strain
sensor (ZSS), whereby lithography eliminates the randomness and violent
tearing process inherent in conventional crack sensors and allows
for short periodicity between gaps with gentle sidewall contacts,
critical in high strain sensing enabling operation over an unprecedentedly
wide range. Our sensor achieves a gauge factor of over 15,000 at an
external strain of εext = 18%, the highest known
value. With the uniform gaps of four-to-ten thousand nanometer widths
characterized by periodicity and strain, this approach has far reaching
implications for future strain sensors whose range is limited only
by that of the flexible substrate, with non-violent operations that
always remain below the tensile limit of the metal.