Abstract
Optoelectronic tweezers (OET) or light-patterned dielectrophoresis (DEP) has been developed as a micromanipulation technology for controlling micro- and nano-particles with applications such as cell sorting and studying cell communications. Additionally, the capability of moving small objects accurately and assembling them into arbitrary 2D patterns also makes OET an attractive technology for microfabrication applications. In this work, we demonstrated the use of OET to manipulate conductive silver-coated Poly(methyl methacrylate) (PMMA) microspheres (50 μm diameter) into tailored patterns. It was found that the microspheres could be moved at a max velocity of 3200 μm/s, corresponding to 4.2 nano-newton (10−9 N) DEP force, and also could be positioned with high accuracy via this DEP force. The underlying mechanism for this strong DEP force is shown by our simulations to be caused by a significant increase of the electric field close to the particles, due to the interaction between the field and the silver shells coating the microspheres. The associated increase in electrical gradient causes DEP forces that are much stronger than any previously reported for an OET device, which facilitates manipulation of the metallic microspheres efficiently without compromise in positioning accuracy and is important for applications on electronic component assembling and circuit construction.
Highlights
The current technology to assemble discrete components into electronic circuits is mainly based on surface-mount technology (SMT), which uses a mechanical manipulator arm with a vacuum tip to pick and place the components on to target circuit board[1]
We report the use of a new cost-effective assembly technology based on a touch-less opto-electro-fluidic technique known as optoelectronic tweezers (OET), which has the potential to perform parallel assembling of micro-objects with high accuracy
We present the results of successful manipulation and assembly of large (50 micron diameter) silver-coated Poly(methyl methacrylate) (PMMA) microspheres by positive DEP force using an OET device
Summary
The current technology to assemble discrete components into electronic circuits is mainly based on surface-mount technology (SMT), which uses a mechanical manipulator arm with a vacuum tip to pick and place the components on to target circuit board[1]. Previous research has examined the utility, for this application, of optical tweezers[2], dielectrophoresis (DEP) based on patterned metal electrodes[3,4], Langmuir-Blodgett assembly techniques[5], atomic force microscopy probe[6], and transfer printing technology[7,8] To date, these techniques have relevant drawbacks; they cannot assemble micro-objects with a sufficiently wide range of sizes due to the limitation of exerted force[2,3,4]; they are typically unable to selectively manipulate large numbers of individual objects in parallel[3,4,5]; they are unable to perform highly accurate assembly[3,4,5]; they require complex and expensive positioning equipment[7,8]; they are unable to assemble objects with fragile structures due to the requirement of physically contacting and catching the targeted objects using stamp or tip[7,8]. The strong DEP forces facilitate manipulation of the metallic microspheres efficiently without compromise in positioning accuracy, which is important for applications on electronic component assembling and circuit construction
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