| Description |
Previous studies have shown that nanoparticle separation may be achieved to very high resolution based on size and other properties in a sawtooth-patterned gradient insulator-based dielectrophoretic microfluidic device. This work integrates this dielectrophoretic capture of nanoparticles from a liquid sample with the label-free visualization of the capture process using single-particle light scattering. In this work, nanoparticle tracking analysis (NTA) was used to visualize the movement and capture of fluorescent nanoparticles 10-20 nanometers in diameter (quantum dots) in the "sawtooth" dielectrophoresis device in real time by imaging the laser light scattered by individual particles. This capability of tracking individual particles was used to explore the feasibility of separating very small particles of two different sizes using this technique. Preliminary results show that quantum dot capture is possible at the narrowest gates when 650 volts were applied to shortened channels and when 1000 volts were applied for full-length channels, and that this capture may be successfully visualized using NTA. The visualization of the capture process is greatly enhanced when tracking fluorescent particles. In this case, an appropriate filter may be selected to allow the transmission of fluorescently emitted light while reducing the interference of the background scattering with the visualization of the nanoparticle capture. Furthermore, it was demonstrated that 30 nanometer diameter gold particles are ostensibly captured at 500 volts at a different device gate than similarly sized quantum dots, indicating that separation of mixed samples at different gates is feasible. The merits of several different techniques for device preparation, inspection, and integration with NTA are also discussed, along with the proper use of NTA for this application. |
