Sheng-Chung Yang

Removal of SU-8 photoresist using buckling-driven delamination assisted with a carbon dioxide snow jet for microfluidics fabrication

A new, environmentally friendly, inexpensive and non-destructive method for removing SU-8 after being an electroplating mold in microfluidic fabrication is demonstrated in this paper. A controllable thermal delaminating method assisted by an efficient high-speed aerosol jet consisting of two major steps, delamination followed by removal by lifting, is presented. Experiments with the thermal process, operated at a rising temperature ΔT of 340 °C for 30 min, were carried out. Four delaminations were observed and the critical buckling stresses were calculated to be 38.98, 35.24, 42.04 and 41.26 MPa, respectively. The results show that these delaminations occurred at a rising temperature ΔT of 290, 260.5, 314.7 and 308.5 °C, respectively. The morphology of the thermal buckling-driven delamination was edge initiated and straight sided. The effects of the carbon dioxide (CO2) snow jet at a distance of 10 mm from the nozzle exit as well as the lift force Fdp, drag force Fd and impact force Fi were determined to be 79 × 10−3 N, 0.625 × 10−3 N and (1.65–4.95) × 10−3 N, respectively. Based on the analysis of the lift, drag and impact forces, the lifting force dominates the effects of the CO2 snow jet and is tens of times larger than the others. The experiments and analyses showed that the best distance for the CO2 snow jet to the nozzle exit was 6–10 mm.

Optimization of Gene Transfection Condition using Taguchi Method for an Electroporation Microchip

This study has demonstrated the optimization of an electroporation (EP) system for gene transfection by using the Taguchi method. The parameters of the EP system, which could have an influence on the transecting rate, were optimized, resulting in values of 50 mum electrode gap, 80 mug/mL pEGFP-Nl concentration, 6 V pulse voltage, and 2-pulse. A larger-the-better Omega transformation was employed for better additivity. The analyzed results of interaction A times C, A times D, and C times D showed that there were strong interactions on level 3 of factors A, C, and D to each others. Using optimized EP system, the pEGFP-Nl plasmid was successfully transfected into the basal cell carcinoma cell line (BCC) with 40.36% average transecting rate.

Measurement of DNA Hybridization by Nano-Deformation of Microcantilever in CMOS Biosensor

A 1 cm × 1 cm biosensor chip for analyzing DNA hybridization is developed by CMOS process. The sensor chip has 6 measurement regions, each region with 3 pairs of parallel microcantilever of 125 × 60 × 0.75μm. The microcantilever is a 4-layer structure composed of an immobilized surface layer, a top insulation layer, an embedded piezoresistive layer, and a bottom insulation layer to measure the nano-deformation induced by the surface-assemble monolayer of alkanethiols on Au. By the Langmuir adsorption model, the estimated adsorption rate of the ssDNA is 0.005sec−1 . The design has intrinsic sensitivity needed in biochemical applications such as detecting nucleotide polymorphism and single base mutation to sequence DNA. The capability of in-situ, multipoint measurement promise many frontiers to be explored.Copyright

On the temperature compensation of parallel piezoresistive microcantilevers in biosensors

Microcantilever with embedded piezoresistor has been applied to in-situ surface stress measurement of biochemical reaction, where parallel microcantilever design by using an active cantilever for biosensing and another reference cantilever for noise cancellation has previously been proposed. This paper shows that the measurement is sensitive to the temperature effect induced by the piezoresistor. The temperature difference between the two cantilevers can reach 40°C at 10V operation because of their difference thermal capacitance. For the microcantilever of 125×65×0.75 μm, the offset voltage of the parallel microcantilever is 1.65 mV and the temperature drift is 0.01 mV/°C. An improved parallel microcantilever design is developed using the stripe pattern design on the immobilized layer and the signal conditioning circuit for temperature compensation in biosensors. Analyses and experiments show that the performance of a CMOS sensor chip can be significantly improved.Copyright