Thermoresponsive Hydrogel with Thermal Memory.

Area of Science:

• Materials Science
• Polymer Chemistry
• Biomimetic Materials

Background:

• Biological systems exhibit thermal plasticity, dynamically altering properties based on thermal history.
• Synthetic hydrogels lack this ability, limiting their adaptability and resemblance to biological materials.
• Coral symbiont acclimatization provides inspiration for bio-inspired thermal memory systems.

Purpose of the Study:

• To engineer synthetic hydrogels with thermal plasticity, emulating biological thermal memory.
• To develop a feedback loop enabling hydrogels to encode and respond to thermal history.
• To explore applications of these thermally plastic hydrogels (TP-gels).

Main Methods:

• Developed polyvinyl butyral-based TP-gels with a bioinspired feedback loop.
• Utilized thermoresponsive equilibrium swelling to encode thermal history.
• Employed elastic network constraints to program phase transition thresholds (T_c).
• Exploited temperature-dependent polymer-water miscibility for adaptive swelling and multi-stable states.
• Suppressed spinodal decomposition using elasticity to stabilize metastable states during thermal encoding.

Main Results:

• Achieved reversible opacity transitions in TP-gels with programmable T_c shifts of 3-7 °C per cycle.
• Demonstrated multi-stable states through adaptive swelling, encoding thermal history.
• Successfully leveraged TP-gel plasticity for cryptographic applications, including sequential information decryption.
• Showcased spatially resolved T_c gradients acting as thermodynamic keys for decryption.

Conclusions:

• Established a paradigm for materials with embodied environmental intelligence by bridging biological adaptability and synthetic systems.
• Demonstrated the potential of thermodynamic metastability engineering in creating adaptive materials.
• Highlighted the significance of TP-gels for advanced applications requiring environmental responsiveness and memory.