Droplet suspension technology builds a dynamic equilibrium field to allow liquid-phase substances to stably levitate in a gas-phase environment. As the resistance to motion is extremely low when in a levitated state, the moveability of the substance will be excellent. If the droplet suspension technology is used in the microfluidics technology, high-precision control of levitating substances at a micro scale can be realized. This technology can be used in many areas such as biological detection, medical and pharmaceutical analysis, nanometer materials composition and optical spectroscopy testing. At present, the droplet suspension technology is limited by the complexity of the suspension system and the special suspension conditions. As a result, high-precision and high-freedom control of tiny liquid droplets is very difficult.

Recently, Professor Chen Rong, Professor Liao Qiang and Professor Zhu Xun from the School of Energy and Power Engineering of Chongqing University and Jiao Long, a doctoral candidate, have proposed a photoinduced suspension droplet control technology based on optical microfluidics. The single beam is used to realize quantified generation, size regulation and high-precision motion control of 10-12-10-15-level levitated droplets. Researchers have revealed the decisive effect of “gas-phase capturing trap” resulting from local photothermal effect on the generation and control of levitated droplets, and used the single focused beam as the “optical baton” to realize high-precision control of non-linear variable motion and start and stop of levitated droplets in a labyrinth-type grid interface. This technology is also applicable to control of levitated droplets containing various types of biochemical reagents. Researchers hope that the research would offer new ideas and approaches for transmission of complicated materials and reaction in-situ and analysis.

Photoinduced “gas-phase capturing trap”

Visualized presentation of levitated droplets

High-precision motion of levitated droplets in the labyrinth-type grid interface

Related research findings have been recently published by Journal of Physical Chemistry Letters as an inside cover paper, and has been published by Nature Reviews Chemistry, a sub-journal of Nature, as a Research Highlight paper. Professors Chen Rong, Liao Qiang and Zhu Xun of Chongqing University are corresponding co-authors. Doctoral Candidate Jiao Long is the first author.

This research project has been funded by the National Natural Science Foundation (No. 51576021, No. 51620105011), the Cultivation Program of Outstanding Reserve Talents for Scientific Research of Chongqing University (No. CQU2017HBRC1A01), and operational fund for basic scientific researches in colleges and universities allocated by the central government (No. 2018CDXYDL0001).

Link of the paper published by Journal of Physical Chemistry Letters:

https://pubs.acs.org.ccindex.cn/doi/10.1021/acs.jpclett.8b03699

Link of the coverage by Nature Reviews Chemistry:

https://doi.org/10.1038/s41570-019-0091-5