We investigated the potential for using polydimethylsiloxane microfluidic devices in a biological assay to explore the cellular stress response (CSR) associated with hyperthermia induced by exposure to laser radiation. In vitro studies of laser-tissue interaction traditionally involved exposing a monolayer of cells. Given the heating-cooling dynamics of the cells and nutrient medium, this technique produces a characteristic “bulls-eye” temperature history that plagues downstream molecular analyses due to the nonuniform thermal experience of exposed cells. To circumvent this issue, we devised an approach to deliver single cells to the laser beam using a microfluidic channel, allowing homogeneous irradiation and collection of sufficient like-treated cells to measure changes in CSR after laser heating. To test this approach, we irradiated Jurkat-T cells with a 2-μm-wavelength laser in one branch of a 100-μm-wide bifurcated channel while unexposed control cells were simultaneously passing through the other, identical channel. Cell viability was measured using vital dyes, and expression of HSPA1A was measured using reverse transcription polymerase chain reaction. The laser damage threshold was 25±2 J/cm 2 , and we found a twofold increase in expression at that exposure. This approach may be employed to examine transcriptome-wide/proteome changes and further comparative work across stressors and cell types.
Graphene, one of the recently discovered carbon nanostructures, has shown good piezoresistive properties. One of the most important areas of research for graphene sheets, in terms of basic science and application in strain or stress sensors, is the measurement of gauge factors. The gauge factors of various layers of graphene sheets are measured based on the equivalent stress beam. The measurement is carried out using a beam-bending method to detect the change in resistance of graphene sheets in different bending states. The gauge factor ranges from 10 to 15, depending on the number of layers in the graphene sheet. These results reveal the piezoresistance effect of single- and multi-layer graphene sheets, which will be of benefit in the fabrication of microsensors. The resistance of graphene sheets decreases as temperature increases from 20°C to 60°C, and the gauge factor is not very sensitive to changes in environmental temperature.
This paper presents a new comb-drive actuator arrangement that has a large displacement with low driving voltage and
relatively small footprint. The new arrangements in the comb drivers can provide both pulling forces and pushing forces
as compared to conventional drivers that only provide pulling forces, therefore additional displacements are achieved
without increasing the driving voltage. This arrangement is verified numerically using FEM and the simulation results are consistent with the values derived from the mathematical model. The results show an obviously enhanced displacement and a compact layout.