Highly Conductive Silicone Elastomers via Environment‐Friendly Swelling and In Situ Synthesis of Silver Nanoparticles

Abstract

Flexible and stretchable conductors are crucial components for next‐generation flexible devices. Wrinkled structures often have been created on such conductors by depositing conductive materials on the pre‐stretched or organic solvent swollen samples. Herein, water swelling is first proposed to generate the wrinkled structures on silicone elastomers. By immersing silicone/sugar hybrid in water, a significant amount of swelling occurs as a result of osmosis and capillary interactions with the sugar and silicone matrix. Considering the drastic swelling effect and controllable swelling ratio, water swelling is used to replace the conventional pre‐stretching and organic solvent swelling to fabricate stretchable conductors. In situ growing of silver nanoparticles (AgNPs) is carried out on the swollen silicone elastomers. Wrinkled conductive silicone elastomers are successfully constructed after removing the residual water. The conductive elastomer has a sheet resistance of less than 1 Ω sq‐1 at zero strain and also shows high sensitivity when subjected to external deformation up to 100% strain. The silicone/sugar composite also possesses good 3D printability with the desired shear‐thinning property. Human motion detection is demonstrated using the 3D printed sensors. This work provides a facile and environment‐friendly strategy to fabricate superior flexible and stretchable sensing devices.

3D Printed Silicones with Shape Morphing and Low-Temperature Ultraelasticity

“…The dissolving of the embedded salt particles created an osmotic pressure between the soaking medium and the high concentration solution in the pores originally occupied by salt particles. Driven by the osmotic pressure, more water would diffuse into the pores and enlarge them, giving rise to the macroscopic swelling of the printed sample until the maximum size . Meanwhile, enlargement of the pore size led to increase of retractive force from the stretched rubber matrix, and the embedded salt solution would slowly exchange with the soaking medium through the interconnected pores.…”

Wrinkled Interfaces: Taking Advantage of Anisotropic Wrinkling to Periodically Pattern Polymer Surfaces

“…In a given solvent atmosphere, the swelling effect and its discrepancy in the penetration of the skin and substrate create compressive stress in the skin, forming regular wrinkles. [ 62 , 134 , 135 , 136 , 137 ] Swelling‐induced wrinkling is a reversible process where the solvent controls the disappearance and regeneration of the wrinkles. The rheological properties of the polymer and the geometry of the diffusion front make a crucial contribution to controlling the final wrinkle dimensions and orientation.…”

Advances in constructing silver nanowire-based conductive pathways for flexible and stretchable electronics

“…Due to their superior conductivity, high transmittance, and excellent flexibility, silver-based materials have been extensively explored as a suitable alternative candidate for next-generation flexible electrodes. [15][16][17] Various morphologies of silver nanomaterials, such as 0-D silver nanoparticles (AgNPs), [18][19][20] 1-D silver nanowire (AgNWs), [21][22][23] and 2-D silver flakes (AgFs), [24][25][26] have been employed in the flexible/stretchable devices.…”

“…Based on these reported works, a new method is proposed to utilize 3D printing and water-induced polymer swelling to fabricate 3D wrinkled stretchable sensors. 20,207 In this method, soluble powders and commercial silicone polymers are selected to formulate the printing ink which is 3D printed to form customdesigned patterns and structures. The printed patterns are soaked in an aqueous solution, where a dramatical swelling is created under the action of osmotic pressure as the doped powder is released.…”