Photothermal Plasmonic Actuation of Micromechanical Cantilever Beams

Abstract

Oscillations of charge carriers in plasmonic metal nanoparticles activated by resonant absorption of light are accompanied by local temperature increase due to nonradiative plasma damping. The control of this photothermal effect is considered essential for many applications ranging from photochemistry or nanomedicine to chemical and physical sensing. Here, we present a study on the conversion of visible light into mechanical energy via photothermal plasmonic and nonplasmonic effects. Atomic force microscopy cantilevered sensors coated with various materials and excited in vacuum by a wavelength tunable laser show that light generates a resonant mechanical oscillation. The photoinduced oscillation amplitude depends on the wavelength of the incident light, allowing for an optimization of energy conversion based on absorption spectroscopy of the coating material. The effect of nonphotonic forces acting on the cantilever is probed in the context of photoinduced force microscopy by placing the cantilever in interaction with a substrate surface at various distances. The findings are relevant for any technique utilizing an optical actuation of a mechanical system, and for photoinduced force detection methods in particular.