This paper proposes a bimorph piezoelectric vibration energy harvester (PVEH) with a flexible 3D meshed-core elastic layer for improving the output power while lowering the resonance frequency. Owing to the high void ratio of the 3D meshed-core structure, the bending stiffness of the cantilever can be lowered. Thus, the deflection of the harvester and the strain in the piezoelectric layer increase. According to vibration tests, the resonance frequency is 15.8% lower and the output power is 68% higher than in the conventional solid-core PVEH. Compared to the solid-core PVEH, the proposed meshed-core PVEH (10 mm × 20 mm × 280 μm) has 1.3 times larger tip deflection and the maximum output power is 24.6 μW under resonance condition at 18.7 Hz and 0.2G acceleration. Hence it can be used as a power supply for low-power-consumption sensor nodes in wireless sensor networks.
In this study, we propose a solidified ionic liquid with a 3D microstructure to increase its surface area for the performance enhancement of a vibration energy harvester (VEH). By soft lithography in MEMS technologies, the use of a mold is proposed to perform the solidification, polarization, and microstructure transfer of the solidified ionic liquid simultaneously. We fabricated six samples with different surface shapes and sizes to compare the power generation performance characteristics of VEHs using a solidified ionic liquid. According to a vibration test, the performance of the VEH with nanometer roughness was improved at a 10 Hz frequency. Also, the output power of the VEH with a micro-folded hollow conical structure was improved at a 50 Hz frequency.
We investigated the shape of a well to trap single cells for the purpose of improving the cell trapping rate after cell seeding and liquid exchange in a cell microarray. The wells having vertical and inclined tapered side‐wall were made using three‐dimensional UV photolithography. Changes in cell trapping rate by the shape of the wells were evaluated by trapping tests with fluorescent microbeads and living cells. As a result of trapping test with living cells, bead residual rate of the microarray with inclined tapered wells is up to 2.9 times higher than that with vertical wells.
In this study, we fabricated a flexible 3D mesh structure with periodic voids by using a 3D lithography method and applying it to a vibration energy harvester to lower resonance frequency and increase output power. The fabrication process is mainly divided into two parts: three-dimensional photolithography for processing a 3D mesh structure, and a bonding process of piezoelectric films and the mesh structure. With the fabricated flexible mesh structure, we achieved the reduction of resonance frequency and improvement of output power, simultaneously. From the results of the vibration tests, the meshed-core-type vibration energy harvester (VEH) exhibited 42.6% higher output voltage than the solid-core-type VEH. In addition, the meshed-core-type VEH yielded 18.7 Hz of resonance frequency, 15.8% lower than the solid-core-type VEH, and 24.6 μW of output power, 68.5% higher than the solid-core-type VEH. The advantage of the proposed method is that a complex and flexible structure with voids in three dimensions can be relatively easily fabricated in a short time by the inclined exposure method. As it is possible to lower the resonance frequency of the VEH by the mesh structure, use in low-frequency applications, such as wearable devices and house appliances, can be expected in the future.
This paper describes a microfluidic device for observation of cancer cell invasion induced by chemotaxis. The developed device has two main channels, the channel filled with cell suspension and the channel filled with solution containing chemotactic factor. These channels are connected via tapered orifice structures to capture multiple cancer cells in it to form cell clusters. Observation of cell invasions affected by cell adhesions is possible with this device. The devices were fabricated by using threedimensional lithography and PDMS (polydimethylsiloxane) molding. Invasion cells leaving the cell clusters and moving to the channel containing chemotactic factors through the orifices were successfully observed on the device.
K E Y W O R D Scancer cell clusters, cancer cell invasion, microfluidic device, soft lithography, three-dimensional lithography
A new driving scheme for AC type ultra high pressure mercury lamp has been developed. The new driving scheme provides a highly stabilized arc over thousands of hours without any fluctuations of light output due to the current modulation. The design freedom of the color sequential projection optics expands dramatically.
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