Optoelectronic Manipulation, Trapping, Splitting, and Merging of Water Droplets and Aqueous Biodroplets Based on the Bulk Photovoltaic Effect

Abstract

Optical and optoelectronic techniques for micro-and nano-object manipulation are becoming essential tools in nano-and bio-technology. A remarkable optoelectronic technique that has experimented a strong development in the last few years is the so called photovoltaic optoelectronic tweezers. It is based on the light-induced electric fields generated by the bulk photovoltaic effect in certain ferroelectrics such as LiNbO3. The technique is simple and versatile, enabling a successful manipulation of a large variety of micro-and nano-objects with only optical control, without the need of electrodes or power supplies. However, it is still a challenge for this tool, to handle objects immersed in aqueous solution due to the electric screening effects of polar liquids. This has hindered their application in biotechnology and biomedicine where most processes develop in aqueous solution. In this work, a new efficient route to overcome this problem has been proposed and demonstrated. It uses photovoltaic optoelectronic tweezers to manipulate aqueous droplets, immersed in a non-polar oil liquid, but hanging at the interface air-oil. In this singular configuration, the high electric fields generated in the photovoltaic substrate allow a simple and flexible manipulation of aqueous droplets controlled by the light. Droplet guiding, trapping, merging and splitting have been achieved and efficient operation with water and a variety of biodroplets (DNA, sperm, and PBS solutions) have been demonstrated. The reported results overcome a main limitation of these tweezers to handle bio-materials and promises a high potential for biotechnological and biochemistry applications including their implementation in optofluidic devices.

Parallel Manipulation and Flexible Assembly of Micro-Spiral via Optoelectronic Tweezers

“…Compared with the traditional assemble method ( Fragouli et al, 2014 ; Li et al, 2016 ), this is easy to manipulate the micro- spirulina to form more specific shapes in one application device. Furthermore, utilizing the capacity of selecting OETs ( Zhang et al, 2018 ; Puerto et al, 2020 ), the specific size design of assembly of micro- spirulina could sort from more samples improving the efficiency. In the future, we propose that the flexible assembly of the complex shape of micro-spiral by the OET system may be appropriate for assembling the complex vessel model structure.…”

“…Optoelectronic tweezers, different from conventional non-contact micro-/nanomanipulation technology [e.g., magnetic control ( Lin et al, 2016 ; Dai et al, 2021 ), ultrasonic manipulation ( Zhang W. et al, 2021 ), dielectrophoresis ( Collet et al, 2015 ), and optical tweezers ( Cheah et al, 2014 )], utilize visual patterns to form virtual optical electrodes in a photoelectric layer. Then, it can generate a non-uniform electric field to achieve parallel independent manipulation of particles ( Chiou et al, 2005 ), and adjusting the visual patterns can flexibly manipulate a large number of micro-/nano-objects ( Liang et al, 2020 ; Puerto et al, 2020 ; Chu et al, 2021 ), such as cells ( Yang et al, 2010 ; Chu et al, 2020 ), microorganisms ( Mishra et al, 2016 ), and gold nanoparticles ( Jamshidi et al, 2009 ). In addition, OETs can generate a primarily driven force with a low light intensity compared to optical tweezers by using light-induced dielectrophoresis.…”

Droplet Ejection and Liquid Jetting by Visible Laser Irradiation in Pyro‐Photovoltaic Fe‐Doped LiNbO3 Platforms

“…[27][28][29] Another interesting alternative based in undoped lithium niobate reports 2D droplet manipulation by photo-activated pyroelectric fields in the near infrared. [30,31] On the other hand, several works [32,33] report droplet manipulation by the so called photovoltaic optoelectronic tweezers. [34,35] Among them, reference [33] introduce a very efficient and versatile approach particularly suitable for water and aqueous droplets containing biological materials.…”

“…[30,31] On the other hand, several works [32,33] report droplet manipulation by the so called photovoltaic optoelectronic tweezers. [34,35] Among them, reference [33] introduce a very efficient and versatile approach particularly suitable for water and aqueous droplets containing biological materials. [36] The technique uses the light-induced electric fields (bulk photovoltaic effect) generated mainly in Fedoped lithium niobate crystals.…”

Integrated Assembly and Photopreservation of Topographical Micropatterns

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These assembly techniques are useful, but they also rely on expensive and specialized positioning tools and well-trained personnel, and can be limited by material properties and throughput.Optical assembly is an alternative strategy to assemble functional structures from micro-and nano-objects as building blocks. [9] Optical assembly relies on optical micromanipulation technologies such as optical tweezers, [9][10][11][12][13] opto-thermophoretic tweezers, [14][15][16] photovoltaic tweezers, [17][18][19][20] and optoelectronic tweezers, [21][22][23][24][25][26][27][28][29][30] in which micro-and nano-objects are optically assembled into a pattern in a fluidic environment and later dried for use in various applications. This approach has advanced rapidly in recent years, and preserves many of the advantages of the conventional methods while being easy-to-implement and allowing for cost-effective operation.

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