Jingdong Chen

A multi-frequency sandwich type electromagnetic vibration energy harvester

We proposed a multi-frequency sandwich type vibration energy harvester to widen the effective frequency range of vibration energy harvester. The harvester is composed of three resonant structures with different natural frequencies. The resonant structures are two cantilevers each with bi-layer coils and a plane spring with a magnet. The maximum peak-peak voltages of the three different frequencies are 172 mV, 104 mV, and 112 mV at the frequencies of 235 Hz, 330 Hz, and 430 Hz, respectively. The first maximum voltage is much higher than the others, because the coils in both cantilevers can produce voltages.

Progress of Microfluidics for Biology and Medicine

Microfluidics has been considered as a potential technology to miniaturize the conventional equipments and technologies. It offers advantages in terms of small volume, low cost, short reaction time and highthroughput. The applications in biology and medicine research and related areas are almost the most extensive and profound. With the appropriate scale that matches the scales of cells, microfluidics is well positioned to contribute significantly to cell biology. Cell culture, fusion and apoptosis were successfully performed in microfluidics. Microfluidics provides unique opportunities for rare circulating tumor cells isolation and detection from the blood of patients, which furthers the discovery of cancer stem cell biomarkers and expands the understanding of the biology of metastasis. Nucleic acid amplification in microfluidics has extended to single-molecule, high-throughput and integration treatment in one chip. DNA computer which is based on the computational model of DNA biochemical reaction will come into practice from concept in the future. In addition, microfluidics offers a versatile platform for protein-protein interactions, protein crystallization and high-throughput screening. Although microfluidics is still in its infancy, its great potential has already been demonstrated and will provide novel solutions to the high-throughput applications.

A microfluidic chip for direct and rapid trapping of white blood cells from whole blood

Blood analysis plays a major role in medical and science applications and white blood cells (WBCs) are an important target of analysis. We proposed an integrated microfluidic chip for direct and rapid trapping WBCs from whole blood. 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 by the arrays of trapping structures. We fabricated the PDMS (polydimethylsiloxane) chip using soft lithography and determined the critical flow velocities of tartrazine 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. The time taken for complete lysis of whole blood was about 85 s under the flow velocity 0.05 μl/min. The RBCs were lysed completely by mixing and the WBCs were trapped by the trapping structures. The chip trapped about 2.0 × 10(3) from 3.3 × 10(3) WBCs.

Separation of circulating cancer cells by unique microfluidic chip in colorectal cancer.

Circulating tumor cells (CTCs) from peripheral blood are emerging as a useful tool for the detection of malignancy, monitoring disease progression, and measuring response to therapy. We describe a unique microfluidic chip that was capable of efficient and selective separation of CTCs from peripheral whole blood samples. The ability of microfluidic chip to capture CTCs from PBS and whole blood samples was tested. Sixty-eight peripheral blood samples from 68 colorectal cancer patients were investigated for the presence of CTCs by microchip technology. The frequency of CTCs was analyzed statistically for correlation with relevant clinical data. We also examined samples from 20 healthy individuals as controls. The calculated capture efficiency was 85.7% and decreased significantly at flow rates above 2.0 ml/h. The number of CTCs isolated ranged from 3 to 236/ml for colorectal patients [99 +/- 64 (mean +/- SD) CTCs/ml]. None of the 20 healthy subjects had any identifiable CTCs. We identified CTCs in 46 (67.65%) of the 68 patients: in two of nine (22.22%) Dukes A, in 10 of 24 (41.67%) Dukes B, in 21 of 22 (95.45%) Dukes C, and in all 13 Dukes D patients. The detection rate in Dukes C and D patients was much higher than in Dukes A and B patients (97.73% vs. 36.36%) (p < 0.01). A significant correlation between detection of CTCs and clinical stage (r = 0.792, p < 0.01) was found, which was higher than carcinoembryonic antigen (r = 0.285, p > 0.01), carbohydrate antigen 19-9 (r = 0.258, p > 0.01), alpha-fetoprotein (r = 0.096, p > 0.01), and cancer antigen 125 (r = 0.134, p > 0.01). Microfluidic chip provides a novel method for capturing CTCs. The presence of CTCs correlated with clinical stage. It is important to evaluate CK-positive and DAPI-stained tumor cells together to determine the role of CTCs in tumor behavior and disease progression.

Bubble generation and mechanism in polydimethylsiloxane based polymerase chain reaction chip

In order to explain the mechanism of bubble generation in polydimethylsiloxane (PDMS), we investigated the crucial factors: the surface wettability and permeability of PDMS. Two microfluidic chips were designed and fabricated: a PDMS/glass chip and a glass/PDMS/glass sandwich chip (about 1 μm in thickness of PDMS). Then, two sets of experiments were carried out: a comparison between the PDMS/glass chips untreated and treated with O2 plasma, and another comparison between a PDMS/glass chip and a glass/PDMS/glass sandwich chip. The bubble in the PDMS/glass chip was avoided by treating with O2 plasma. After the treatment, the residual gas between the PDMS surface and water was eliminated in that the PDMS surface became hydrophilic. In addition, the gas molecules required higher energy to enter the chambers due to the reduced contact angle of PDMS and water. The glass/PDMS/glass sandwich chip was treated with the vacuum processing to eliminate the residual gas. And the gas outside of the chip did not enter th...