ABEL trap circuit analysis and upgrades
Engineering
Applied Optics Group - Stem Diversity Program – CAMP Undergraduate Research
In the past, the Applied Optics lab developed an Anti-Brownian Electrokinetic (ABEL) trap with which microscopic particles could be manipulated on a chip with very low power [1]. New research projects at the lab require not only the use, but also improvements of this trap which works by alternatingly sending two laser beams through optical waveguides into the chip to excite a fluorescent particle in a fluidic channel. Based on the relative magnitude of the fluorescence, an electronic feedback signal is applied across the channel to compensate for any particle movement away from the trapping point. At its heart, this apparatus is controlled by an electronic circuit that needed to be repaired and improved upon. To this end, I performed a thorough analysis of its components, analyzed its functions, rebuilt the circuit and installed updated components. During this process a number of issues with the original setup were discovered and fixed. In addition, I improved the physical layout to facilitate future repairs and improvements, as well as addressing some wiring neatness that could be compromised by daily use. The circuit was then tested until it was fully functional and incorporated with the optical detection setup.
The complete trapping system is now ready for new use in conjunction with an integrated nanopore to select, trap and study single biological molecules such as viruses and ribosomes on an optofluidic chip.
Currently, I am working on documenting the performance of the box to assess the needed improvements for a revision model of the box. I intend to use a cheap microcontroller to have improved performance and control over the clock board speed, currently at ~3μsec with a NC555 timer. With a microcontroller such as the ChipKit32 with a 80Mhz processor, I should be able to achieve clock speeds down to about 13nsec with better accuracy than the 555 timer. Consequently, the use of a microcontroller will open the possibilities to have a user interface and customizable settings, which may be required depending on the particle of interest.
[1] Kühn, S., B. S. Phillips, E. J. Lunt, A. R. Hawkins, and H. Schmidt. "Ultralow Power Trapping and Fluorescence Detection of Single Particles on an Optofluidic Chip." Lab on a Chip 10.2 (2009): 189. Print.
