Microfluidic chips were designed and fabricated to capture cells in a relative small volume to generate the desired concentration needed for analysis. The microfluidic chips comprise 3D cell capture structures array fabricated in PDMS. The capture structure includes two layers. The first layer consists of spacers to create small gap between the upper layer and glass. The second layer is a sharp corner U-shaped compartment with sharp corners at the fore-end. And another type capture structure with Y-shaped fluidic guide has been designed. It was demonstrated that the structures can capture cells in theory, using Darcy-Weisbach equation and COMSOL Multiphysics. Then yeast cell was chosen to test the performance of the chips. The chip without fluid guides captured approximately 1.44×105 cells and the capture efficiency was up to 71%. And the chip with fluid guides captured approximately 5.0×104 cells and the capture efficiency was approximately 25%. The chip without fluid guides can capture more cells because the yeast cells in the chip without fluid guides are subject to larger hydrodynamic drag force.

Electroencephalogram (EEG) has been one of the important means to study brain functions and diseases.We fabricated an innovative MEMS elastic-based dry electrode using photolithography and electroforming process.The pitch of elastic-based dry electrode tip is 100 lm.We adopted polydimethylsiloxane as an elastic layer which provides the flexibility when the conductive layer and the electrode tip contact with the skin. This kind of dry electrode array does not need conductive gel during testing procedure. Compared with the traditional Ag/AgCl wet electrode, it greatly reduced the preparation time for EEG measurement and it could make the examinee more comfortable.

The nuclear magnetic resonance (NMR) probe has great influence on signal transmission and reception in NMR technology applications. In this paper, we present a design, fabrication, and test of an NMR probe comprised of a multilayer planar microcoil with a polydimethylsiloxane (PDMS) microchannel. First, geometric parameters of the probe are determined through theoretical analysis. Second,based on a glass substrate, the multilayer planar microcoil is manufactured using repeated photolithography and electroplating processes. During the fabrication process,the polyimide layer is used to package the coil, and the PDMS interlayer is used to adjust the distance from centerlines between the coil and the sample chamber. Third,the resistance and the quality factor of the coil are found to be 1.2158 X and 7.217, respectively, at a Larmor frequency of 28.1 MHz. Finally, the NMR probe is tested in an NMR experiment. The transverse relaxation time T2 for the solid PDMS is 20.6 ± 0.4 ms, which is in agreement with 21.1 ± 0.2 ms obtained by a Bruker Minispec MQ60.Results show that the design and fabrication of this NMR probe are feasible for time-domain NMR applications.

tThis article introduces a novel type of MEMS probe card that uses polymer (polydimethylsiloxane, PDMS)as an elastic layer. The elastic layer provides the flexibility when the probes are in contact with the chippads. Through-holes in the PDMS and the low temperature co-fired ceramic (LTCC) substrate lead thesignals or power to the back side of the LTCC substrate. The proposed MEMS probe card configurationpotentially improves the probe density and simplifies the fabrication process. The probes are formedby electroplating on the PDMS substrate. The PDMS elastic substrate probe card with a probe pitch of100 m was developed for area array pad testing. The contact force is approximately 18 mN when theprobes overdrive is 20 m. Coplanar waveguides structures can be fabricated on the PDMS surface. Themeasured insertion loss is 0.2 dB at 3 GHz.The test data exhibited that the PDMS elastic substrate probecard is suitable for high-frequency wafer level IC testing.

Blood analysis plays a major role in medical and science applications and white blood cells (WBCs) are most often the target of analysis. We proposed an integrated microfluidic chip for rapid trapping WBCs from whole blood directly. The microfluidic chip consists of two basic functional units: a winding channel to mix and arrays of two-layer trapping structures to trap WBCs. Red blood cells (RBCs) were eliminated through moving the winding channel and then WBCs were trapped using the arrays of trapping structures. The microfluidic chip was fabricated in the biologically compatible PDMS (polydimethylsiloxane) using MEMS (microelectromechanical system) fabrication technology. We determined the critical flow velocities of tartrazine water and brilliant blue water mixing and whole blood and red blood cell lysis buffer mixing in the winding channel. They are 0.25 μl/min and 0.05 μl/min, respectively. The critical flow velocity of the whole blood and red blood cell lysis buffer is lower due to larger volume of the RBCs and higher kinematic viscosity of the whole blood. Under this flow velocity, the RBCs were lysed completely by mixing and the WBCs were trapped by the trapping structures.