Innovative wearable solutions: Semi-releasing ion-conductive lignin hydrogel sensors for enhanced practicability

Area of Science:

• Materials Science
• Biomedical Engineering
• Polymer Chemistry

Background:

• Impurities on wearable devices degrade hydrogel sensor performance and longevity.
• Effective management of surface adhesion is crucial for reliable signal transmission.

Purpose of the Study:

• To develop an ion-conducting hydrogel sensor with tunable adhesion properties.
• To address challenges of impurity adhesion and signal interference in wearable electronics.

Main Methods:

• Formulation of a hydrogel using deep eutectic solvents (choline chloride and acrylic acid) with lignin.
• Creation of a "semi-releasing material" with one adhesive and one non-adhesive side.
• Treatment with aluminum chloride (AlCl₃) solution to modify adhesive properties.

Main Results:

• The lignin-containing hydrogel exhibited high adhesion energy (427.1 J/m²) and UV resistance.
• AlCl₃ treatment eliminated adhesiveness, enhancing fracture elongation and tensile strength via a metal-phenolic network.
• The hydrogel functioned as a reliable strain sensor for human activity monitoring with environmental tolerance and conductivity.

Conclusions:

• The developed hydrogel offers a versatile "semi-releasing" approach to mitigate impurity adhesion issues in wearable sensors.
• The tunable adhesion and enhanced mechanical properties present a feasible strategy for improving flexible electronic devices.