Efficient and Robust Fabrication of Soft Sensors via Injection With Auxiliary Suction in Multilayered Microchannels With a Liquid Metal Alloy

From 2011 to August 2024, 795 papers have utilized liquid metals like eutectic gallium-indium alloy (EGaIn) or Galinstan in microfluidic systems, flexible electronics, and soft robotics, as reported in the Scopus database. The most common manufacturing techniques include manual needle injection, stencil printing, direct writing, and vacuum filling, with manual needle injection being the most prevalent due to its simplicity and cost-effectiveness. However, this method often results in high failure rates and inconsistent outcomes due to manual variability. Other techniques also present challenges, such as high setup costs and limitations based on material stiffness. To address these issues, a needle injection with auxiliary suction method has been introduced. This approach enhances manufacturing success and consistency, especially in multi-layered microchannel structures with varying material stiffness. The incorporation of auxiliary suction reduces fabrication time by 25.3% and decreases pressure on the microfluidic channels by 10.3%, leading to more stable and reliable production of multi-layered microchannel soft sensors. This method is expected to significantly advance liquid metal-based applications by providing a more efficient, affordable, and reliable fabrication process.