3D printed multifunctional hierarchical structured cellular silicones with ultraelasticity, extreme load-bearing capacity, shape morphing and sensing properties

3D printed hierarchical structured cellular silicones with high mechanical performance, shape morphing properties, multifunctional piezoresistive and temperature sensing properties were reported. The hierarchical structured PDMS/TEM cellular silicones demonstrated 3D printed lattice structure and micro-scaled porous filaments which was achieved upon thermal expansion of microspheres. The optimal 3D printed hierarchical structured silicones showed extreme load-bearing capacity (load is more than 165000 times its weight), ultra-high elasticity (negligible stress and strain loss under 80% compression), and high cycle durability (less than 4% strain loss under 1000 compression cycles). Besides, shape morphing property was endowed to the silicones to manufacture complex structures facilely. Furthermore, piezoresistive effect and varying temperature-sensing properties were endowed to the silicones by adding conductive fillers as MWCNTs, which demonstrate excellent versatility of this method in potential applications such as soft and wearable sensors. [Display omitted] Multifunctional lightweight cellular silicone with adjustable properties has aroused great interests in many fields. However, it remains a challenge to facilely prepare multifunctional lightweight porous silicones with high load-bearing capacity. Herein, this work developed a 3D printing technique to prepare lightweight hierarchical structured cellular silicones with macroscale lattice structure and microscale intra-strand close-cell porosities, which was achieved by the expansion of thermally expandable microspheres (TEM) with plastic shells dispersed in formulated silicones. The obtained silicone foam with hierarchical porosity distributions shows excellent mechanical properties, including extreme load-bearing capacity (load is more than 165000 times its weight), high elasticity (negligible stress and strain loss under 80% compression), and high cycle durability (less than 4% strain loss under 1000 compression cycles). Besides, the incorporation of conductive fillers of MWCNTs endowed the foam with multifunctional piezoresistive and temperature-sensing properties. Furthermore, by printing multiple mixture inks of varying expansion ratios, shape morphing ability was endowed to the printed foam, to achieve complex curvature geometry facilely, demonstrating excellent versatility and potential applications in manufacturing flexible and conformal electronics of this method.