Flexible Iontronic Pressure Sensor Based on Ammonium Bicarbonate In-Situ Pore-Forming Porous Ionic Gel

Area of Science:

• Materials Science and Engineering
• Polymer Chemistry
• Sensor Technology

Background:

• Conventional methods for fabricating microstructures (photolithography, 3D printing) are costly.
• Physical/chemical pore-forming techniques often leave impurity residues.
• Existing capacitive sensors suffer from limited sensitivity.

Purpose of the Study:

• To develop a low-cost, in situ gas foaming strategy for fabricating porous thermoplastic polyurethane (TPU)-based ionic gels.
• To create high-performance ionic flexible sensors with enhanced sensitivity and durability.
• To enable large-scale, cost-effective production of wearable sensors for various applications.

Main Methods:

• Utilized ammonium bicarbonate as a pore-forming agent in a low-temperature in situ gas foaming process.
• Synthesized composite ionic gel substrates by blending TPU with [EMIM][TFSI] ionic liquid.
• Fabricated flexible substrates using a graphene-filled PDMS slurry and modified electrodes via oxygen plasma treatment.

Main Results:

• Achieved a high sensitivity of 25.3 kPa⁻¹ across a 0-1000 kPa range with R² = 0.992.
• Demonstrated rapid response (60 ms) and recovery (80 ms) times with <3% degradation after 1000 cycles.
• Successfully validated in vivo wearable applications, including pulse monitoring, swallowing detection, and motion sensing.

Conclusions:

• The proposed low-temperature in situ gas foaming strategy offers a novel, cost-effective route for producing high-performance ionic flexible sensors.
• The dual synergistic enhancement from the porous structure and modified electrodes significantly improves sensor performance.
• The fabrication process is scalable, fault-tolerant, and suitable for industrial mass production, with broad applications in wearable technology and human-machine interfaces.