Visible -Light-Gated Reconfigurable Rotation of Nanomotors in Electric Fields

TL;DR

This paper introduces a visible-light-controlled mechanism for reconfiguring the rotation of semiconductor nanowires in electric fields, enabling dynamic, reversible, and efficient nanomotor control for various nanodevice applications.

Contribution

It presents the first demonstration of light-tunable rotation of nanomotors in electric fields, combining experimental, theoretical, and simulation analyses for understanding and utilizing this effect.

Findings

Rotation speed can be instantly increased, decreased, or reversed by light intensity.

The mechanism is based on optically tunable polarization of Si nanowires.

The effect enables non-contact differentiation of semiconductor and metallic nanostructures.

Abstract

Highly efficient and widely applicable working mechanisms that allow nanomaterials and devices to respond to external stimuli with controlled mechanical motions could make far-reaching impact to reconfigurable, adaptive, and robotic nanodevices. Here, we report an innovative mechanism that allows multifold reconfiguration of mechanical rotation of semiconductor nanoentities in electric (E) fields by visible light stimulation. When illuminated by light in the visible to infrared range, the rotation speed of semiconductor Si nanowires in electric fields can instantly increase, decrease, and even reverse the orientation depending on the intensity of the applied light and the AC E-field frequency. This multifold rotation configuration is highly efficient, instant, and facile. Switching between different modes can be simply controlled by the light intensity at an AC frequency. An array of experimentations, theoretical analysis, and simulations are carried out to understand the underlying principle, which can be attributed to the optically tunable polarization of Si nanowires in aqueous suspension and an external electric field. Finally, leveraging this newly discovered effect, we successfully differentiate semiconductor and metallic nanoentities in a non-contact and non-destructive manner. This research could inspire a new class of reconfigurable nanoelectromechanical and nanorobotic devices for optical sensing, communication, molecule release, detection, nanoparticle separation, and microfluidic automation.