  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, whereby lithography eliminates
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 unprecedently wide
range. Our sensor achieves a gauge factor of over 15,000 at {\epsilon}ext=18%,
the highest known value. With the uniform gaps of three-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.
