Scientists have developed the first photovoltaic tweezers.

Optical tweezers provide unique opportunities for research in physics, biology, and medicine. They enable manipulation of the tiniest and most delicate objects that cannot be held in the traditional sense.

However, such devices require high-intensity laser beams, complex electrodes, and low-conductivity media for operation. These limitations impede the widespread use of optical tweezers.

A team of scientists led by Dr. Du Xuemin from the Shenzhen Institute of Advanced Technology (SIAT) of the Chinese Academy of Sciences has introduced a new photopyroelectric tweezer (Photopyroelectric Tweezer, PPT) that utilizes the properties of light and electric fields to manipulate matter. The research has been published in the journal The Innovation.

The tweezer developed by the researchers consists of two key components: a near-infrared laser radiation source and a system that includes a liquid medium and a photopyroelectric substrate.

The photopyroelectric substrate is made from composites containing microparticles of liquid metals, gallium, and indium. The researchers embedded them in poly(vinylidene fluoride-co-trifluoroethylene) (LMPs/P(VDF-TrFE)) and coated them with a low-friction lubricant layer. The polymer layer generates surface charges in real-time due to the photopyroelectric effect — the phenomenon of electric field generation when the material is irradiated, while the lubricant layer reduces resistance to movement and prevents charge shielding by the conductive medium.

The thoughtful design of the photopyroelectric tweezer effectively and reliably creates surface charges when exposed to low-intensity infrared radiation, up to 8.3 milliwatts per square millimeter. Using such radiation, the scientists achieved a powerful driving force from the tweezer of up to 0.46 micronewtons without the need for high-intensity laser beams, complex electrode structures, and additional power sources.

The new tweezer allows for remote and precise manipulation of objects made from various materials (polymers, inorganic substances, and metals), in different states (bubbles, liquids, and solids), and geometric shapes (spheres, cuboids, and wires). Moreover, it adapts to media with a wide range of conductivities and is suitable for both macroscopic platforms and microscopic systems. The system created by the scientists facilitates movements in areas ranging from 5 micrometers to two and a half millimeters, enabling control over solid objects, liquid droplets, and biological samples, from individual cells to their clusters.

The photopyroelectric tweezer developed by the scientists opens new avenues in robotics, colloidal chemistry, biology and medicine, tissue engineering, and neuroscience.