The novel micromixer is manufacture

The novel micromixer is manufactured from polydimethylsiloxane (PDMS) based on the soft lithography technique in the clean room. At the beginning, the silicon wafer is cleaned and modified by specific steps. Then, the SU-8 photoresist is coated on the silicon wafer by a spin coater (SC-1B) at 1500 rpm/s to get the requested height of the microchannel. After exposure and development by the standard UV aligner (URE-2000/25) and development solution, respectively,the SU-8 master mold of 100±5μm thickness is acquired. Then, the PDMS solution and curing agent (Luo Diya Corp., V-3040A and V-3040B) are fully mixed with a weight ratio of 10:1 by the vacuum mixer. During this process, the air bubbles in the PDMS mixture are removed. Then, the PDMS mixture is poured into the master mold and cured at 85 °C for 30 min in a vacuum drying oven (DUG-9070A). The PDMS replica is achieved which is peeled off from the master mold. At last, the PDMS layer containing the micromixer pattern is bonded to a blank PDMS layer using oxygen plasma treatment (JYS-A) to form a sealed three-dimensional microchannel. The three inlets and one outlet are drilled in advance. Fig. 2(a) shows a photograph of the fabricated PDMS chip used in this experiment. And the optical micrograph of the fabricated micromixer is shown in Fig. 2(b).