A high-temperature
thin/thick-film strain gauge (TFSG) shows development
prospects for in situ strain monitoring of hot-end components due
to their small perturbations, no damage, and fast response. Direct
ink writing (DIW) 3D printing is an emerging and facile approach for
the rapid fabrication of TFSG. However, TFSGs prepared based on 3D
printing with both high thermal stability and low temperature coefficient
of resistance (TCR) over a wide temperature range remain a great challenge.
Here, we report a AgPd TFSG with a glass–ceramic protective
layer based on DIW. By encapsulating the AgPd sensitive layer and
regulating the Pd content, the AgPd TFSG demonstrated a low TCR (191.6
ppm/°C) from 50 to 800 °C and ultrahigh stability (with
a resistance drift rate of 0.14%/h at 800 °C). Meanwhile, the
achieved specifications for strain detection included a strain sensing
range of ±500 με, fast response time of 153 ms, gauge
factor of 0.75 at 800 °C, and high durability of >8000 cyclic
loading tests. The AgPd TFSG effectively monitors strain in superalloys
and can be directly deposited onto cylindrical surfaces, demonstrating
the scalability of the presented approach. This work provides a strategy
to develop TFSGs for in situ sensing of complex curved surfaces in
harsh environments.