January 1, 2014.
Microfluidic chips are used to separate particles of differing sizes. A piezoelectric transducer is attached to the silicon chip and produces an ultrasonic standing wave in the channel of the chip. The overall width of the chip is 900μm and has a thin wall 300μm from one side. As a sample passes through the chip, the larger particles are concentrated at the low pressure node of the standing wave while the smaller particles are not affected by the wave. The stream of large particles is directed into a separate output than the rest of the sample. When the chips are fabricated, there are small variations in the dimensions of the wall. This leads to each chip acting slightly differently in laboratory tests. The goal of these simulations is to determine the effect of the wall shape and dimensions on the focusing frequency and position. Two dimensional simulations were done in COMSOL Multiphysics using four different wall shapes over a range of 10μm around the actual dimensions of 13μm and 6μm measured from a sample chip. The wall dimensions are taken as the lengths of the top and bottom of the wall. The shape of the wall does not affect focusing frequency. As the difference in the wall dimensions increases, focusing frequency increases and focusing position moves farther from the wall.
Lawrence Livermore National Laboratory (LLNL)
This material is based upon work supported by the S.D. Bechtel, Jr. Foundation and by the National Science Foundation under Grant No. 0952013. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the S.D. Bechtel, Jr. Foundation or the National Science Foundation. This project has also been made possible with support of the National Marine Sanctuary Foundation. The STAR program is administered by the Cal Poly Center for Excellence in Science and Mathematics Education (CESaME) on behalf of the California State University (CSU).