News Source & Photographer: School of Mechatronical Engineering

Editor: News Agency of BIT

Translator: Xu Qiannan, News Agency of BIT

Recently, Professor Zhang Shuailong of IT published a review article titled "Optoelectronic tweezers: a versatile toolbox for nano-/micro-manipulation" in the top international biochemistry journal Chemical Society Reviews (IF=60.615) and was selected as the main cover of the journal. This paper systematically introduces the principle, chip structure and system construction of photoelectric tweezers technology, demonstrates the application in the fields of cell manipulation, micro and nano materials assembly, medical detection and nano/micro-machines, and reviews the industrialization progress of this technology (as shown in Figure 1). Finally, the paper summarizes the application prospect, limitation and future development trend of this technology. The first author and corresponding author of this paper is Professor Zhang Shuailong of the School of Mechatronical Engineering, the second author is Xu Bingrui, a doctoral candidate from the School of Mechatronical Engineering, Grade 2022. BIT is the only author’s affiliation. The paper was also supervised by Professor Liu Lianqing of Shenyang Institute of Automation, Chinese Academy of Sciences, Professor Huang Qiang of BI T, Professor Wu Ming of University of California, Berkeley (inventor of photoelectric tweezers) and Professor Aaron Wheeler of University of Toronto.

Figure 1. Introduction of photoelectric tweezers technology from four aspects, including technical principle, device structures, application scenario and the commercialization of the technology.

In 2005, inspired by the optical tweezer technology, Professor MingWu's team of the University of California, Berkeley, invented the photoelectric tweezers technology. The optical tweezers technology requires the use of a laser light source to control an object, while photoelectric tweezers technology relies on the light-induced to generate a non-uniform electric field and only LED light sources are needed to achieve manipulation of tiny targets. Compared with optical tweezers, photoelectric tweezers can control objects of larger scale and has the advantage of parallel control of multiple small targets. Because of these features, photoelectric tweezers technology can be widely used in the screening of specific particles, the array arrangement, separation and transportation of small objects, and has a wide range of applications in biomedical, nano-/micro- processing, biochemical sensing, nano-/micro- robots and other fields. In this review paper, the author first reviews the development history of photoelectric tweezers technology and introduces the system and technical principle of photoelectric tweezers in detail.

Figure 2. Schematic diagram of photoelectric tweezers and physical diagram of photoelectric tweezers chip

Figure 2 shows the technical schematic diagram of the photoelectric tweezers and the physical diagram of the photoelectric tweezers chip. The photoelectric tweezers chip is generally composed of two ITO conductive glass substrates, on which a photoconductive layer a-Si: H (hydrogenated amorphous silicon) is plated. When a solution containing a nano-/micro- object is transferred to the chamber of the photoelectric tweezer chip, an alternating current and a light spot are applied to the photoelectric tweezer device, and an electric field will be generated under the induction of the light spot. The interaction between non-uniform electric fields and a nano-/micro- object can create a dielectric electrophoretic force, thus controlling the spatial position of the nanometer/micron object. Photoelectric tweezers is a micro-nano control technology that combines the light field with the electric field by utilizing the photoelectric effect of semiconductor materials. It has a number of advantages such as programmability, flexibility, versatility, high-throughput and ease of integration with other characterization systems. It is a very advanced optical control technology.

Figure 3. Manipulation and assembly of nanoscale objects using photoelectric tweezers

Photoelectric tweezers systems are commonly used for the manipulation and assembly of micro-/nano-scale objects. This technology has been used in a variety of nanomaterials, including but not limited to semiconductors and metal nanowires, carbon nanotubes, graphene nanosheets, conducting nanoparticles, and metal ions. Figure 3 illustrates the manipulation and assembly of various nanoscale objects using a photoelectric tweezers system. Meanwhile, photoelectric tweezers have also been used to manipulate a variety of micro-scale objects ranging from several microns to several hundred microns, including dielectric/metal particles, oil/water droplets, and bubbles. The assembly of miniature electronic and photonic components through photoelectric tweezers is also an important application of photoelectric tweezers technology. Figure 4 shows various applications for assembling metal spheres and semiconductor lasers using the photoelectric tweezers technology. The results of the experiment show that the photoelectric tweezers assembly technology has no impact on the performance of these devices.

Figure 4. Assembly of electronic and optoelectronic components using photoelectric tweezers

In the field of biology, photoelectric tweezers technology also has a wide range of applications. These applications include but are not limited to manipulation, isolation and analysis of individual cells/molecules, analysis and acquisition of intrinsic cell properties, electroporation, fusion and lysis of cells, and the preparation of biological tissue materials. The photoelectric tweezers technology can directly manipulate DNA molecules, protein molecules, cells and so on. In the field of cell manipulation, photoelectric tweezers technology is often used to manipulate different types of cells and study the motion behavior of these cells under different experimental conditions (Figure 5). Meanwhile, other cell manipulation techniques based on photoelectric tweezers are also rapidly developing, such as large-scale cell array technology, intracellular drug delivery, and cell transfection. With more than ten years of development, photoelectric tweezers technology has become an important technical tool in the field of cell manipulation, cell analysis and cell surgery.

Figure 5. Manipulation and separation of cells using photoelectric tweezers

The photoelectric tweezers technology can also be combined with other microfluidic technologies, such as channel microfluidic, digital microfluidic, and photoelectric wetting technology. By integrating the photoelectric tweezers technology with the microfluidic technology in one system, the microfluidic device can be controlled to continuously transport samples to the area where the photoelectric tweezers work (Figure 6), enabling high-throughput rarget sorting, separation, and processing based on the photoelectric tweezers technology. Meanwhile, photoelectric tweezers technology is also often integrated with other micro-manipulation technologies, such as traditional dielectric electrophoresis technology, acoustic tweezers, micro and nano robots, etc. (Figure 7). This integration improves the flexibility of photoelectric tweezers technology to control small targets, and expands the application field of photoelectric tweezers technology.

Figure 6. Microfluidic technology integrated with photoelectric tweezers

Figure 7. Photoelectric tweezers integrated with other micromanipulation techniques

The paper also introduces the industrial transformation of photoelectric tweezers technology and its application in the field of antibody drug development (as shown in Figure 8). At present, the commercial platform Beacon (developed by BerkeleyLights Company) based on photoelectric tweezers technology has been widely used in cell line screening, cell therapy, synthetic biology and antibody development, and has been purchased by many leading pharmaceutical companies in the world. The Beacon platform can effectively improve the screening efficiency of functionalized cell lines and greatly shorten the research and development time of antibody drugs, and has been applied to screen neutralizing antibody drugs against the novel coronavirus.

Finally, the paper summarizes the direction of application and technical advantages and disadvantages of the photoelectric tweezers technology, and made a prospect on the future development direction of the photoelectric tweezers technology.

Figure 8. Industrialization of photoelectric tweezers technology

Paper information attached:

Shuailong Zhang*，Bingrui Xu, Mohamed Elsayed, Fan Nan, Wenfeng Liang, Justin K. Valley, Lianqing Liu, Qiang Huang, Ming C. Wu and Aaron R. Wheeler. Optoelectronic tweezers: a versatile toolbox for nano-/micro-manipulation. Chemistry Society Reviews 2022, 51, 9203–9242.

Paper Address:https://doi.org/10.1039/D2CS00359G

Author’s introduction attached:

Zhang Shuailong received his bachelor degree from BIT and his doctorate degree from the University of Strathclyde in the UK. He has been engaged in postdoctoral research in the University of Glasgow in the UK and the University of Toronto in Canada. He was awarded the 2019 Overseas High-level Talents Program (Youth Project). His research interests include biological micro-nano operating system, photoelectric tweezers technology, digital microfluidic technology, biomedical detection and translational medicine and has published more than 60 high-level papers in international journals such as PNAS, NatureCommunications, ScienceAdvances, ChemicalSocietyReviews, Small and other top international conferences, and participated in the writing of two English monographs. As the project leader and main participant, He hosted and participated in many scientific research projects funded by the National Natural Science Foundation, the Natural Sciences and Research Association of Canada (NSERC) and the Engineering and Physical Research Society of Britain (EPSRC), and participated in the incubation and industrialization transformation of many companies.

Xu Bingrui is a doctoral student from the School of Mechatronical Engineering, BIT. She has been awarded the honors of Beijing Outstanding Graduate and China Agricultural University Outstanding Graduate. Her research interests cover photoelectric tweezers technology, microbial behavior, and biological micro-nano manipulation.