New Approach Uses Light Instead of Robots to Assemble Electronic Components

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The researchers used optoelectronic tweezers because this optical manipulation approach can form thousands of traps at once, offering the potential of massively parallel assembly. The tweezers are formed using a layer of silicon that changes its electrical conductivity when exposed to light. In the areas exposed to points of light, a non-uniform electric field forms that interacts with particles or beads in a liquid layer on top of the silicon, allowing the particles to be precisely moved by moving the point of light. Creating patterns of light points allows multiple particles to be moved simultaneously.

“Using our method, we can move solder beads measuring from the nanometer range up to about 150 microns,” said Zhang. “We have been able to move objects that are over 150 microns, but it’s more challenging because as the size of the object increases, the frictional force also increases.”

After using the optoelectronic tweezers to assemble a pattern of 40-micron-diameter, commercially available solder beads, the researchers froze the liquid in the optoelectronic tweezer device and then reduced the surrounding pressure to allow the frozen liquid to turn from a solid directly into a gas. This freeze-drying approach allowed the assembled solder beads to remain fixed in place after the liquid was removed. The researchers say it can be used to remove liquid used with any type of optical trap, or even traps formed with acoustic waves.

In addition to assembling the solder beads into different lines, the researchers also demonstrated parallel assembly of several beads and used the beads to form electrical connections. The solder beads exhibit a strong dielectric force, which means they can be moved accurately and fast, allowing very efficient assembly of structures.

The researchers are now working to turn their laboratory-based system into one that would combine the optoelectronic tweezer and freeze-drying process in a single unit. They are also developing a software interface to control the generation of a light pattern based on the number of particles that needed to be trapped.

“We are now using a computer to generate the light pattern to move the beads, but we are working on an app that would allow a tablet or smart phone to be used instead,” said Zhang. “This could allow someone to sit away from the system and use their finger to control the movements of the particles, for example.”

Neale recently received funding to continue this line of research by using the new optical micromanipulation approach to create high energy density capacitors to replace batteries in mobile devices.

About Optics Express

Optics Express reports on new developments in all fields of optical science and technology every two weeks. The journal provides rapid publication of original, peer-reviewed papers. It is published by The Optical Society and edited by Andrew M. Weiner of Purdue University. Optics Express is an open-access journal and is available at no cost to readers online at: OSA Publishing.

About The Optical Society

Founded in 1916, The Optical Society (OSA) is the leading professional organization for scientists, engineers, students and business leaders who fuel discoveries, shape real-life applications and accelerate achievements in the science of light. Through world-renowned publications, meetings and membership initiatives, OSA provides quality research, inspired interactions and dedicated resources for its extensive global network of optics and photonics experts.

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