A high-performance pressure sensor enabled by a sodium alginate bilayer hydrogel via tailored unit ring-opening

Area of Science:

• Materials Science
• Biomaterials Engineering
• Sensor Technology

Background:

• Gradient-structured hydrogels are crucial for converting mechanical stimuli into electrical signals, mimicking human skin.
• Designing hydrogels with controlled gradient properties for precise signal transduction remains a significant challenge.

Purpose of the Study:

• To develop a novel bilayer hydrogel with a gradient structure for high-performance motion sensing.
• To investigate the tunability of sensor performance by controlling material properties.

Main Methods:

• Fabrication of a bilayer hydrogel using layer-by-layer assembly of unmodified sodium alginate (SA) and oxidized SA (OSA).
• Characterization of the mechanical and electrical properties of the gradient hydrogel.
• Evaluation of the hydrogel as a motion sensor, assessing sensitivity, sensing range, stability, and programmability.

Main Results:

• The bilayer hydrogel exhibits high toughness and modulus in the bottom layer (unmodified SA) and enhanced softness/flexibility in the top layer (OSA).
• The fabricated sensor demonstrates high sensitivity (46.3 Pa⁻¹, 0-1 kPa), a broad sensing range (up to 120 kPa), and excellent stability (1000 cycles at 40% strain).
• Sensor performance, including sensitivity and detection range, can be precisely tuned by adjusting the oxidation degree of OSA.

Conclusions:

• The developed gradient hydrogel offers a feasible strategy for designing advanced soft sensors.
• This work opens new avenues for applications requiring precise mechanical-to-electrical signal conversion, inspired by biological systems.