Real‐Time Operation of Photovoltaic Optoelectronic Tweezers: New Strategies for Massive Nano‐object Manipulation and Reconfigurable Patterning

Optical and optoelectronic techniques for micro‐ and nano‐object manipulation are becoming essential tools in nano‐ and biotechnology. Among optoelectronic manipulation platforms, photovoltaic optoelectronic tweezers (PVOTs) are an emergent technique that are particularly successful at producing permanent nanoparticle microstructures. New strategies to enhance the capabilities of PVOT, based on real‐time operation, are investigated. This optoelectronic platform uses z‐cut LiNbO3:Fe substrates under excitation by a Gaussian light beam. Unexpected results show that during illumination, metallic particles previously deposited on the substrate are ejected from the light spot region. This behavior differs from the trapping phenomenon observed in previous work on PVOT operation, using a sequential method in which illumination is prior to particle manipulation. To discuss the results, a novel mechanism of charge exchange between particles and the ferroelectric substrate is proposed. Applications of this repulsion behavior are investigated. On the one hand, either particle repulsion or trapping in the illuminated region can be obtained by simply light switching on/off. On the other hand, by moving the light spot, different kinds of arbitrarily shaped tracks along the light path, either empty or filled with particles, are obtained. The results demonstrate new key capabilities of PVOT, such as pattern drawing, erasure, and reconfiguration. New optoelectronic strategies for massive nano‐object manipulation and reconfigurable patterning are demonstrated. All novel functionalities are based on the singular photoelectric properties of LiNbO3:Fe that include high photoinduced electric fields and effective interaction between the nano‐objects and the ferroelectric surface. Thereby, it is proved that this material is an outstanding substrate that remarkably enhances the capabilities of photovoltaic optoelectronic tweezers.