Photothermally Driven High-Speed Crystal Actuation and Its Simulation

Area of Science:

• Materials Science
• Crystallography
• Photomechanics

Background:

• Mechanically responsive crystals are typically actuated via photoisomerization.
• Photoisomerization exhibits limitations including slow speeds, inability to actuate thick crystals, and a narrow usable wavelength range.

Purpose of the Study:

• To report photothermally driven fast-bending actuation and simulation of a salicylideneaniline derivative crystal.
• To demonstrate the advantages of photothermal actuation over photoisomerization for crystal bending.

Main Methods:

• Investigated thin (<20 μm) and thick (>40 μm) salicylideneaniline derivative crystals under UV and visible light irradiation.
• Utilized femtosecond transient absorption to estimate photothermal energy generation.
• Employed a one-dimensional nonsteady heat conduction equation for simulation of photothermal bending.

Main Results:

• Thick crystals exhibited rapid bending (milliseconds) via photothermal effect, unlike photoisomerization.
• Achieved high-frequency bending at 500 Hz using pulsed UV laser irradiation.
• Successfully simulated photothermal bending, attributing it to a nonsteady temperature gradient.

Conclusions:

• Photothermal actuation offers a faster, more versatile alternative to photoisomerization for crystal bending.
• This approach enables actuation in crystal types and thicknesses previously not possible.
• The photothermal effect is expected to significantly expand the potential and versatility of crystals as actuation materials.