The Smart Polymer Materials group led by Prof. CHEN Tao at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of Chinese Academy of Sciences (CAS), has developed a fully-hydrophobic ionogel which enables high-efficiency wearable underwater sensors and communicators in underwater operations. The study was published in Materials Horizons.

Wearable underwater sensing technology is indispensable to underwater operation, such as marine resource exploration, underwater rescue and underwater construction, owing to the crucial role it plays in ensuring safety and improving efficiency of operation by detecting various signals from human and surroundings.

Thanks to its advantages in tunable mechanical properties, biocompatibility and multifunctionality, ion-conducting gel is among the most promising materials for wearable sensors under low-humidity conditions. However, due to the instability of ion-conducting gel under long-term high-humidity environment, developing wearable sensors applied in underwater  sensing based on the ion-conducting gel still remains challenging,.

To address this issue, researches at NIMTE developed a fully-hydrophobic ion-conducting ionogel via the one-step polymerization of hydrophobic monomers in a hydrophobic IL solvent.

As a wearable underwater sensor, the prepared ionogel showed excellent long-term underwater stability. The diffusion barrier based on fully-hydrophobic structure endowed it with outstanding anti-swelling capacity and suppressed the diffusion of ions effectively. The great hydrophobic properties enhanced the adhesion of ionogel in the underwater environment by destroying the hydration layer, which contributes to the practical application of ionogel sensors.

Performing as a wearable underwater sensor, the prepared ionogel exhibited high sensitivity, wide strain range, superior responsiveness and durability.

As a demonstration, the ionogel sensor can accurately detect the body motions of human and aquatic life in the complex underwater environment, showing the great application potential in the field of posture monitoring and biological research.

By virtue of the coding principle of Morse code, a simple and efficient underwater communicator was proposed by matching finger bending status to the specific meanings (''dots'' and ''dashes'') and monitoring these finger bending motion under the water. Through the continuous combination of finger bending status, a series of underwater messages can be delivered efficiently.

The fully-hydrophobic ionogel shows great potential in marine applications based on its excellent underwater sensing and communication performance, and it also provides a facile and effective route for developing next-generation wearable underwater sensors and communicators.

This work was supported by the National Natural Science Foundation of China (No. 51773215), China Postdoctoral Science Foundation (No. 2021M690157), Key Research Program of Frontier Science, Chinese Academy of Sciences (No. QYZDB-SSW-SLH036), the Sino-German Mobility Program (No. M-0424), and K.C.Wong Education Foundation (No. GJTD-2019-13).

Fig. The fully-hydrophobic ionogel for underwater sensing and communication  (Image by NIMTE)

Contact
WEI Junjie
Ningbo Institute of Materials Technology and Engineering
E-mail: weijunjie@nimte.ac.cn