Hydrodynamic control of silicone elastomers on between porous media

Silicone elastomers, for example, polydimethylsiloxane (PDMS), have been widely used as cross-linkers for fabrication of flexible strain sensors. They not only lend strong adhesion to adjacent materials, for example, porous fabrics, but also tune their elastic property. Silicone elastomer precursors, which are typical non-Newtonian fluids, can easily penetrate into porous fabrics, driven by the capillary effects of fibers. Unfortunately, such a penetration has negative effects on both adhesion strength and elastic property of PDMS, thus limiting their applications. Here we report a facile method for preparing uniform silicone elastomer films, that is, PDMS, on between porous media via controlling the hydrodynamics of elastomer precursors. Our experiments show that the hydrodynamics of elastomer precursors can be easily controlled by modulating the pre-curing time of PDMS precursors to prevent them from penetration into porous media but keep their high adhesion. Based on this hydrodynamic modulation of PDMS precursors, we firmly adhere conductive silver nanowires (AgNWs) onto knitted fabrics, and further combine composites with common clothing from the point of view of ergonomics, showing the possibility of applying such a modulation to the fabrication of wearable strain sensors. Our findings not only present an understanding of liquid transport in porous media, but also provide a novel method of controlling the hydrodynamics of elastomer precursors in porous media for achieving the effective wearable sensors.