Flexible liquid metal display using 3-Aminopropyl triethoxysilane-treated light emitting diodes (LEDs) array

Abstract

In recent years, the fabrication of flexible electronic devices has been focused on the use eutectic gallium‑indium (EGaIn) liquid metal (LM) materials with polydimethylsiloxane (PDMS) microfluidics, which are less toxic. The flexible electronic devices offer the advantage of attaining various shapes as they are liquid at room temperature. However, discontinuities in the circuit occur while bending of the flexible LM circuit as EGaIn LM easily leaks into the space between the electrical components such as light-emitting diodes (LEDs) and PDMS microfluidic channels. Thus, the present study proposes use of a (3-Aminopropyl) triethoxysilane (APTES)-treatment method to create a circuit consisting of 100 μm channels based on EGaIn. The strategy enhances the bonding strength of surface mount device (SMD) such as LEDs and PDMS. The circuit mold to be patterned with the PDMS has been made with a 3D printer and coated with a polymer as buffer layer to allow the PDMS to detach the circuit mold easily. The change in resistance of the EGaIn LM by varying the bending angle from 0° to 60° is presented for one channel through the I-V curves. Additionally, effect of bending on the on/off state of an APTES-treated SMD type LED has been studied. Furthermore, the proposed method has been employed for developing a 5 × 1 LED array circuit. An Arduino has been employed to express a 5 × 5 LED array circuit in the form of letters. Hence, a flexible device with improved stability has been demonstrated using EGaIn LM that does not overflow while bending due to an enhanced binding force between the PDMS and SMD-type LEDs as a result of the APTES-treatment processing.