Microfluidic devices employing dielectrophoresis (DEP) have been widely studied and applied in the manipulation and analysis of single cells. However, several pre-processing steps, such as the preparation of purified target samples and buffer exchanges, are necessary to utilize DEP forces for suspended cell samples. In this paper, a sequential cell-processing device, which is composed of pre-processing modules that employ deterministic lateral displacement (DLD) and a single-cell trapping device employing an electroactive microwell array (EMA), is proposed to perform the medium exchange followed by arraying single cells sequentially using DEP. Two original microfluidic devices were efficiently integrated by using the interconnecting substrate containing rubber gaskets that tightly connect the inlet and outlet of each device. Prostate cancer cells (PC3) suspended in phosphate-buffered saline buffer mixed with microbeads were separated and then resuspended into the DEP buffer in the integrated system. Thereafter, purified PC3 cells were trapped in a microwell array by using the positive DEP force. The achieved separation and trapping efficiencies exceeded 94% and 93%, respectively, when using the integrated processing system. This study demonstrates an integrated microfluidic device by processing suspended cell samples, without the requirement of complex preparation steps.
A thin, flexible, and biocompatible medical ultrasonic transducer was developed using a sok-gel composite spray technique to fabricate a single sheet of piezoelectric material. The careful selection of materials prioritized flexibility, with silicone rubber being chosen for its biocompatibility as the material to be in direct contact with the living body. A porous lead zirconate titanate (PZT) film with a dielectric constant of 134 was generated, and comb-shaped electrodes were printed on the piezoelectric film to form a 64-channel linear array, which successfully suppressed crosstalk values between adjacent elements and at a distance of two elements to -41.5 and -45.8 dB, respectively. Experiments using string targets achieved a spatial resolution of 2 mm in the lateral direction and 0.68 mm in the axial direction. In an imaging experiment of the carotid artery, the transducer was successful in visualizing the vessel wall before and after the carotid artery vessel.
An efficient design method for flip chip ball grid array (BGA) packages has been developed. This method uses design of experiment (DOE), a series of finite element (FE) stress analyses based on an orthogonal array used in DOE, and statistical analysis. By using this method to design a BGA package having 1600 pins, the warpage of the optimum packaging structure is very small and all of the reliability demands are satisfied.
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