Public defence in the field of Engineering Physics, MSc Shanming Hu

Title of the thesis: Thermoresponsive interpenetrating network hydrogels for soft actuation, switchable whiteness and adhesion

Thesis defender: Shanming Hu 
Opponent: Professor Timo Laaksonen, University of Helsinki
Custos: Aalto Distinguished Professor Olli Ikkala, Aalto University School of Science

As the demand for responsive soft materials grows, engineering hydrogels with precise control over mechanical, optical, and interfacial properties remains a significant challenge. This thesis investigates the design and fabrication of advanced thermoresponsive hydrogels by leveraging hierarchical network architectures and multiscale porosity. The research focuses on poly(N-isopropylacrylamide) (PNIPAm) matrices integrated with secondary networks and sacrificial templates to achieve functionalities beyond the scope of conventional soft materials.
Publication 1 introduces thermally trainable dual-network hydrogels. By utilizing the distinct thermal transitions of agarose and PNIPAm, we demonstrate that these materials can be trained to adapt their mechanical responses such as stiffness and work capacity based on their thermal history. This provides a foundation for soft robotic components that exhibit thermoresponsive behaviour.
Publication 2 demonstrates the optical modulation of hydrogels. By employing macro-crosslinking strategies, the pore size distribution of the phase-separated state is optimized to ~350 nm, resulting in a switchable, bright white state with a four-fold increase in reflectance compared to standard gels.
Publication 3 exhibits a dual-template strategy using silica nanowires and agarose employed to engineer multiscale porous hydrogels. The resulting hierarchy of pores (~200 nm and <10 nm) enables broadband reflectance (70%) and facilitates rapid water release at the interface. This architectural synergy allows for robust, switchable underwater adhesion exceeding 20 kPa on diverse surfaces.
In conclusion, this thesis demonstrates strategies for responsive polymers involving sacrificial polymer networks that entangle into interpenetrating networks for developing high-performance, responsive soft materials. The findings offer a robust framework for designing the next generation of smart optical coatings, soft actuators, and responsive adhesive interfaces.

Keywords: Hydrogels, PNIPAm, agarose, thermoresponsive, interpenetrating network, switchable whiteness, underwater adhesion

Thesis available for public display 7 days prior to the defence at Aalto University's public display page. 

Contact information: 
Shanming.hu@aalto.fi 
0504101516