Reversible deformation of a machine holds enormous promise across many scientific areas ranging from mechanical engineering to applied physics. So far, such capabilities are still hard to achieve through conventional rigid materials or depending mainly on elastomeric materials, which however own rather limited performances and require complicated manipulations. Here, we show a basic strategy which is fundamentally different from the existing ones to realize large scale reversible deformation through controlling the working materials via the synthetically chemical-electrical mechanism (SCHEME). Such activity incorporates an object of liquid metal gallium whose surface area could spread up to five times of its original size and vice versa under low energy consumption. Particularly, the alterable surface tension based on combination of chemical dissolution and electrochemical oxidation is ascribed to the reversible shape transformation, which works much more flexible than many former deformation principles through converting electrical energy into mechanical movement. A series of very unusual phenomena regarding the reversible configurational shifts are disclosed with dominant factors clarified. This study opens a generalized way to combine the liquid metal serving as shape-variable element with the SCHEME to compose functional soft machines, which implies huge potential for developing future smart robots to fulfill various complicated tasks.

Electronic skin (e-skin) is attracting huge attention due to its promising applications in diverse fields, including biomimetic machines, artificial intelligence and smart robotics. However, most e-skin circuits involve complicated fabrication processes and high costs. Here, a simple, fast fabrication method for highly conductive (6 × 10⁶ S m⁻¹) and stretchable (above 100%) e-skin based on the adhesion selectivity of a semi-liquid metal (Cu–EGaIn) on laser printed toner and a polymethacrylate (PMA) coating is developed. The stretchable e-skin circuits are shown to transfer to human skin and 3D substrates as wearable electronics for a variety of applications, such as temperature monitoring, interactive devices, and flexible displays. Different from other liquid metal patterning techniques that require expensive equipment or rigid metal traces such as silver nanoparticles, this approach can be used to directly print Cu–EGaIn on a stretchable substrate with a commercial laser printer in seconds. Further, by virtue of the advantage of the high radiological imaging capability of Cu–EGaIn, the e-skin is patterned as a computed tomography (CT) assistant localization marker, which is demonstrated to be very helpful for doctors and surgical robots to efficiently localize a biopsy, which is a core issue in clinics. The present study holds promise for future health care, surgical guidance and personalized entertainment.