Development of eutectic gallium-indium-based transparent conductive electrodes on flexible substrates for touch sensor integration

In this study, the adaptability of liquid metal (LM)-based transparent conductive electrodes (TCEs) to flexible substrates and their potential applications in various electronics fields were investigated. To achieve this, conventional microfabrication techniques were employed to pattern polydimethylsiloxane (PDMS) channels and introduce an Eutectic Gallium-Indium (EGaIn) LM with the aim of enhancing transmittance and reducing sheet resistance. Microfluidic channel structures with varying pitch lengths and widths were fabricated in the types of grid patterns, labeled Pattern A (2000 μm pitch, 40 μm width), Pattern B (2000 μm pitch, 80 μm width), Pattern C (200 μm pitch, 40 μm width), and Pattern D (200 μm pitch, 80 μm width. The corresponding average transmittance values for the EGaIn LM-based TCE were 90 %, 71.8 %, 61.8 %, and 43.2 % for Patterns A, B, C, and D, respectively. To illustrate the potential in touch sensor applications, resistance changes in Patterns A, B, C, and D were assessed under applied forces ranging from 0 N to 150 N, revealing resistance changes of 0.0265 Ω, 0.03617 Ω, 0.03977 Ω, and 0.11629 Ω, respectively.