Shape memory polymers for flexible electronics

Flexible electronics, compared with conventional rigid electronics, have opened up a wide range of applications in wearable devices due to their flexibility and stretchability. However, flexible electronics as the ingenious combination of inorganic brittle electronics and soft elastic substrates are based mainly on two dimensional flat layouts, which limit their further applications. Shape memory polymers, as a class of smart materials are capable of fixing temporary programmed shapes and recovering to their permanent shape upon external stimulations. Their controllable shape changing properties and tunable moduli make them show unique benefits in the field of electronics. The use of shape memory polymers in flexible electronics allows the fabrication of deployable three-dimensional devices and more flexible and controllable device manufacturing typically as transfer printing. Transfer printing, in the field of electronics, is a kind of techniques for selective assembly of micro and nano electronic devices into spatial and functional arrangements. Therefore, shape memory polymers for flexible electronics can either be the flexible substrates for electronics or be the controllable stamps for transfer printing of electronic devices. This paper reviews the recent progress on using shape memory polymers as versatile substrates for flexible electronics and the stamps for transfer printing. Finally, the prospects for their future applications in this important field are described.