Two-wavelength infrared responsive hydrogel actuators containing rare-earth photothermal conversion particles

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Thermoresponsive hydrogels exhibit volume phase transitions with temperature changes.
• Rare-earth-oxide nanoparticles can selectively absorb specific infrared wavelengths.
• Controlling localized heating in hydrogels is key for developing advanced soft actuators.

Purpose of the Study:

• To construct and demonstrate two-wavelength infrared responsive soft actuators.
• To achieve wavelength-selective, localized volume phase transitions in hydrogels.
• To enable controlled, reversible bending motion in soft actuators using distinct infrared wavelengths.

Main Methods:

• Compositing neodymium oxide (Nd2O3) and ytterbium oxide (Yb2O3) particles into a thermoresponsive hydrogel.
• Irradiating the hydrogel composites with specific infrared wavelengths (808 nm and 980 nm) to induce localized heating.
• Fabricating rod-shaped block gels with spatially separated Nd2O3 and Yb2O3 particles to demonstrate selective bending.

Main Results:

• Nd2O3 and Yb2O3 particles enabled independent, localized heating and volume phase transitions at 808 nm and 980 nm, respectively.
• Selective clouding of the hydrogel was observed only at irradiation spots when using the correct particle-wavelength combinations.
• Reversible, wavelength-selective bending motion was achieved in rod-shaped block gels, with specific sides bending based on the applied infrared wavelength.

Conclusions:

• Soft actuators responsive to two distinct infrared wavelengths have been successfully developed.
• The precise control over localized heating and phase transitions opens possibilities for advanced soft robotics and smart materials.
• This technology allows for immediate recovery of transparency upon removal of light, highlighting its reversible nature.