We strive to develop methods that will enable researchers to put their ideas into practice as fast as they can. Towards this goal, we devote our fun time to devise novel and practical methods for rapid fabrication and rapid prototyping. We also publish these work if the method becomes a routine practice in our group. Below are some examples of such projects.
We have introduced a facile and low-cost method for rapid fabrication of PDMS devices. First, we use a laser cutter to pattern the channel design on a spin-coated PDMS layer. Then, using two successive PDMS/PDMS casting steps, we obtain the microfluidic devices. PDMS/PDMS casting can be performed without any chemical surface treatment. Once the mold is fabricated, it can be reused for chip fabrication similar to the silicon/SU-8 molds used in conventional soft lithography. The entire fabrication process is completed in a standard laboratory, and the time required from idea to device testing is only 1.5 h. We believe this method will be especially useful when researchers need multiple channel design iterations for their studies.
We present a very simple method to fabricate three-dimensional (3D) microelectrodes integrated with microfluidic devices. We form the electrodes by etching a microwire placed across a microchannel. For precise control of the electrode spacing, we employ a hydrodynamic focusing microfluidic device and control the width of the etching solution stream. The focused widths of the etchant solution and the etching time determine the gap formed between the electrodes. Using the same microfluidic device, we can fabricate integrated 3D electrodes with different electrode gaps. We have demonstrated the functionality of these electrodes using an impedimetric particle counting setup. Using 3D microelectrodes with a diameter of 25 μm, we have detected 6 μm-diameter polystyrene beads in a buffer solution as well as erythrocytes in a PBS solution. The sample stream is introduced to the system using the same hydrodynamic focusing device, which ensures the alignment of the sample in between the electrodes. This fabrication scheme not only provides a very low-cost and easy method for rapid prototyping, but which can also be used for applications requiring 3D electric field focused through a narrow section of the microchannel.