Opto-Thermoelectric Nanotweezers

Scheme of an extremely low-power optical tweezing technique, termed opto-thermoelectric nanotweezers. (Source: U Texas)

It’s difficult to conceptua­lize a world where humans could casually mani­pulate nano­scale objects at will or even control their own bio­logical matter at a cellular level with light. But that is precisely what Yuebing Zheng, assistant professor of mechanical engi­neering at The Univer­sity of Texas at Austin, is working toward with his nano­tweezers – a new tool for handling nano­particles using light that could create oppor­tunities for inno­vations in nano­technology and indi­vidual health moni­toring.

Building upon several years of research, Zheng and his team from the Cockrell School of Engi­neering have developed opto-thermo­electric nano­tweezers (OTENT) that will help lead to a greater under­standing of matter and bio­logical systems and open a range of possi­bilities for funda­mental and tech­nical inno­vation in nano­photonics. “Until now, we simply did not know how to mani­pulate nano­particles using optical heating,” Zheng said. “With our nano­tweezers, we can not only control particles at the nano­scale, we can also analyze the particles and control the coupling in-situ.”

For one of the demonstrated appli­cations of nano­tweezers, Zheng worked with UT Austin chemical engi­neering professor Brian Korgel. “This project was really interes­ting for me,” Korgel said. “It was led by a group in mecha­nical engi­neering who had discovered a way to mani­pulate indi­vidual nano­particles and nano­wires. Their expertise was in building the photonics machines but not in making the materials to use for the experi­ments. So, my group developed the synthesis of the nano­wires used in the study. It was a great colla­boration.”

Ernst-Ludwig Florin, associate professor of physics and a member of UT’s Center for Nonlinear Dynamics, along with graduate student Emanuel Lissek, provided addi­tional expertise in precision measure­ments by demon­strating the strength of the nano­tweezers. This cooperation between nano­photonics, nano­chemistry and nano­physics research has provided the tools to mani­pulate and analyze nano­particles in ways that have, until now, been beyond our reach. The research team has demon­strated how, using their nano­tweezers, light can be used at the nanoscale in the same way mechanical tweezers are used to handle larger samples.

As a general technique, the nano­tweezers are appli­cable to a wide range of metal, semi­conductor, polymer and dielectric nano­structures with charged or hydro­phobic surfaces. Thus far, researchers have success­fully trapped silicon nano­spheres, silica beads, poly­styrene beads, silicon nanowires, germanium nanowires and metal nano­structures. The further arrange­ment of these nano­materials in a rationally designed manner can lead to a better under­standing of how matter organizes and potential discovery of new func­tional materials.

In a biolo­gical setting, Zheng believes that live cell mani­pulation and cell-to-cell communi­cation will probably be a primary research focus for engineers wishing to exploit the capabilities afforded by the nano­tweezers. “Optimi­zation of the current system to make it bio-compa­tible is the next step of our project,” Zheng said. “We expect to use our tweezers to mani­pulate biolo­gical cells and molecules at single-molecule reso­lution, to control drug release and to study the cell-cell inter­action. The manipu­lation and analysis of bio­logical objects will open a new door to early disease diagnosis and the disco­very of nano­medicine.”

Zheng is confident the tech­nology will be commercia­lized, even to the point where nano­tweezers could be adapted for use in a smartphone app, almost like a modern-day Swiss army knife. “That’s what we hope,” he said. “We also see great oppor­tunities in outreach edu­cation, perhaps for students who want to see what a cell really looks like. In addition, it could be used to assess how healthy one’s immune system is functioning. It has the potential to be an impor­tant mobile diag­nostic tool, giving people more autonomy over their own health care.” (Source: U Texas)

Reference: L. Lin et al.: Opto-thermoelectric nanotweezers, Nat. Phot., online 26 March 2018; DOI: 10.1038/s41566-018-0134-3

Link: Zheng Research Group, Dept. of Mechanical Engineering, The University of Texas at Austin, Austin, USA

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