Photocurable 3D-Printed Hydrophobic Eutectic Gels for Underwater Wearable Sensors

Gel-based conductors have attracted great attention in the field of wearable sensors, due to their flexibility and electrical conductivity. However, these properties of gels are often severely compromised by water molecules, leading to functionality failure in humid or underwater environments. In this study, a hydrophobic eutectogel (PHAEL) is rapidly synthesized via photopolymerization. The preparation involved simultaneously introducing hydrophobic and hydrophilic monomers into a deep eutectic solvent composed of decanoic acid and menthol (DecA/Men). Due to the abundant covalent and hydrophobic interactions within the polymer network, the synthesized PHAEL addresses the shortcomings of conventional eutectogels that are sensitive to water, while enabling good reliable strain-sensing properties both in air and underwater. PHAELs also exhibit high transparency, tunable mechanical properties, and good adhesion. Utilizing digital light processing (DLP) 3D printing technology, the eutectogel can be fabricated into various flexible sensors with intricate structures. These sensors enable underwater Morse code transmission, making them suitable for communication applications. In summary, the design of gels presents new opportunities to develop flexible wearable sensor devices suitable for underwater and extreme environments.