Preparation of Flexible Polymer Sensor Material by Spatial Confining Forced Network Assembly Micro Injection Molding

The development of high-performance flexible pressure-sensing materials necessitates the simultaneous achievement of exceptional flexibility, conductivity, and alignment of microstructure–nanostructure with the mechanical response characteristics inherent to these materials. In this study, we propose a novel method for preparing flexible microneedles as a pressure-sensitive sensor array. First, we obtain conductive composite particles through extrusion granulation, which consists of a compact conductive network with micron-scale filler as the skeleton and nanofiller filling in the gaps within the network. Moreover, by utilizing the “volume exclusion” effect of the microneedle array on the micron-scale filler during injection molding, nanofillers dominate in entering the microneedle. As a result, our molded product exhibits high flexibility and moderate conductivity in its pressure-sensitive area, thereby providing ultrahigh-pressure resistance along with desired response characteristics and sensitivity for sensors. In addition, due to synergistic effects between microscale fillers and nanofillers in nonpressure sensitive bases, a compact conductive network is formed that imparts sufficient conductivity to sensor materials. The method yields sensors with excellent repeatability, high dimensional accuracy, and good consistency, effectively addressing the core application challenges of flexible sensors. The microstructure array flexible sensor fabricated using high-precision injection molding technology offers high efficiency, low cost, and scalability for mass production. Furthermore, the sensitivity of sensors produced by this method is significantly higher—26.6% greater than those made using traditional methods—with a sensitivity as high as 4.71 kPa<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-{1}}$ </tex-math></inline-formula>.