Dynamic Switching of Helical Microgel Ribbons

Area of Science:

• Materials Science
• Soft Matter Physics
• Nanotechnology

Background:

• Poly(N-isopropylacrylamide) hydrogels undergo volume phase transitions with temperature changes.
• Bilayer structures can exhibit complex mechanical responses to environmental stimuli.

Purpose of the Study:

• To investigate the helical coiling behavior of a gold-coated poly(N-isopropylacrylamide) hydrogel ribbon.
• To explore temperature-actuated control over the helix's sense, shape, and dynamics.
• To analyze the system's response under both equilibrium and non-equilibrium conditions.

Main Methods:

• Fabrication of a microscopic bilayer ribbon composed of hydrogel and a thin gold layer.
• Monitoring helical coiling and shape morphing under varying temperatures.
• Utilizing IR-light irradiation to heat embedded gold nanorods for rapid temperature changes (non-equilibrium conditions).
• Analyzing the influence of ribbon dimensions and mechanical properties on coiling.

Main Results:

• The hydrogel ribbon demonstrates temperature-actuated helical coiling with reversible sense reversal.
• Ribbon dimensions and mechanical properties precisely control helix extent and shape.
• Non-equilibrium conditions, achieved via IR-light heating, enable precise spatiotemporal control and deviations from equilibrium paths.
• The system shows sensitivity to temperature and aqueous solution composition.

Conclusions:

• The developed system offers a method for precise, temperature-controlled shape morphing in microscopic hydrogels.
• The ability to dissipate energy and perform work suggests potential applications as a microscopic motor.
• The sensitivity to binding events indicates potential for analyte detection and sensing applications.