Tunable two-step shape and dimensional changes with temperature of a PNIPAM/CNC hydrogel

Area of Science:

• Polymer Science
• Biomaterials Science
• Materials Engineering

Background:

• Poly(N-isopropylacrylamide) (PNIPAM) is a thermo-responsive polymer with a transition near 32°C.
• Cellulose nanocrystals (CNCs) are biocompatible and underutilized in PNIPAM-based hydrogel systems.
• The effect of CNCs on temperature-responsive hydrogel behavior, especially in bilayer systems, remains unexplored.

Purpose of the Study:

• To investigate the impact of cellulose nanocrystals (CNCs) on the thermo-responsive properties of PNIPAM hydrogels.
• To fabricate and characterize PNIPAM/CNC bilayer hydrogels capable of forming tunable 3D geometries.
• To explore the potential of these materials in tissue engineering.

Main Methods:

• Preparation of stable, well-dispersed PNIPAM/CNC suspensions with varying CNC concentrations.
• Electrospinning of suspensions into nanofiber membranes followed by UV-induced crosslinking to form hydrogels.
• Fabrication of bilayer hydrogels using PNIPAM/CNC layers with different CNC proportions.

Main Results:

• CNCs significantly constrained hydrogel swelling above 5 wt% but had a negligible effect on contraction.
• Bilayer PNIPAM/CNC hydrogels formed 3D geometries upon initial water contact due to anisotropic swelling.
• The generated 3D geometries were reversible and tunable via the thickness ratio of the bilayer components.

Conclusions:

• PNIPAM/CNC bilayer hydrogels exhibit controllable shape-morphing capabilities driven by temperature-responsive anisotropic swelling.
• The tunable geometry of these hydrogels makes them highly suitable for tissue engineering scaffolds.
• This work expands the application of CNCs in advanced functional hydrogel systems.