A liquid metal–based shape memory composite with the multi-responsive regulation of solid/liquid adhesion

Switchable liquid adhesion has recently attracted much attention, but the regulation of liquid adhesion generally relies on microstructural tuning or responsive chemistry. Therefore, switchable liquid adhesion on arbitrary substrates is still challenging. Combining controllable solid adhesion is a good strategy for solving the above problem, in which one side of the composite can reversibly adhere to corresponding substrates, while the opposite side can control liquid adhesion. In this paper, we have obtained a multi-layer composite (liquid metal foam/polydimethylsiloxane, LMF/PDMS), where one side is smooth PDMS with adjustable solid adhesion, and the other consists of PDMS pillars with controllable liquid adhesion. LMF/PDMS can be applied to endow various objects with switchable liquid adhesion relying on reversible adhering-detaching ability caused by its shape deformation. Due to the synergy effect of LM and PDMS, the composite exhibits a good shape memory effect under electrical/photic/thermal stimulus, which can reversibly change between the curved and horizontal shapes. Hence, the solid/liquid adhesion on both sides can be reversibly adjusted by the tunable contact area. LMF/PDMS can transport wood and control the stationary position of water droplets on the slide due to switchable adhesion. This adhering-detaching strategy can be extended to construct other types of surfaces. Graphical Abstract