We used inclined lithography to fabricate a pneumatic microvalve for tall microchannels such as those used to convey large cells. The pneumatic microvalve consists of three layers. The upper layer is the actual liquid microchannel, which has a parallelogram-shaped cross section of width 500 μm, height 100 μm, and an acute angle of 53.6°. The lower layer is a pneumatic microchannel that functions as an actuator, and the middle layer is a thin polydimethylsiloxane membrane between the upper and lower layers. The operation of the pneumatic microchannel actuator causes the thin membrane to bend, resulting in the bending of the liquid microchannel and its closure. It was confirmed that the closure of the liquid microchannel completely stopped the flow of the HeLa cell suspension that was used to demonstrate the operation of the microvalve. The HeLa cells that passed through the microchannel were also observed to retain their proliferation and morphological properties.

A microfluidic device capable of precise chemical control is helpful to mimic tumor microenvironments in vitro, which are closely associated with malignant progression, including metastasis. Cancer cells under a concentration gradient of oxygen and other sustenance materials inside a tumor in vivo have recently been reported to increase the probability of metastasis. The influence of glucose concentration on cancer cells has not been measured well, whereas that of oxygen concentration has been thoroughly examined using microfluidic devices. This is because glucose concentrations can be controlled using microfluidic concentration gradient generators, which trade off temporal stability of the glucose concentration and shear stress on the cells; by contrast, oxygen concentration can be easily controlled without microfluidic device-induced shear stresses. To study cell division and migration responses as a function of glucose concentration, we developed a microfluidic device to observe cell behaviors under various chemical conditions. The device has small-cross-section microchannels for generating a concentration gradient and a large-cross-section chamber for cell culture. With this design, the device can achieve both a cell culture with sufficiently low shear stress on cell activity and a stable glucose concentration gradient. Experiments revealed that a low glucose concentration increased the total migration length of HeLa cells and that HeLa cells under a glucose concentration gradient exhibit random motion rather than chemotaxis.

This paper proposes a parallel gripper with a rack and pinion mechanism that is more versatile than traditional parallel grippers with three actuators. The proposed gripper can switch between large and small fingers via lengthening and shortening actions, which improves its ability to pick up objects with various sizes and weights as well as in narrow workspaces. This function also enables the gripper to perform three-face grasping, wherein three faces of a grasped object are securely in contact with the gripper, thereby improving the robustness of grasping. The gripper can also perform in-hand manipulations using a stand. Weanalyze the grasping force of the three-face grasp and show that it is more robust against external forces that generate the moment about the normal of the finger surface than the traditional two-face grasp. Finally, we demonstrate the improved abilities of the developed gripper and the robustness of the three-face grasp through experimental results. The possible applications of this gripper include tasks in which the sizes, weights, and arrangements of the objects are not optimized for robot hands.

The uniform dispersion of cells in a microchamber is important to reproduce results in cellular research. However, achieving this is difficult owing to the laminar flow caused by the small dimensions of such a chamber. In this study, we propose a technique to achieve a uniform distribution of cells using a micropillar array inside a microchamber. The cells deform when they pass through a gap between the micropillars. The deformation causes a repetitive clog-and-release process of cells at the gaps between the micropillars. The micropillar array generates random flow inside the microchamber, resulting in the uniform distribution of the cells via cell accumulation. In the experiment, the distribution of cells in the microchamber with the micropillar array is uniform from end to end, whereas that in the microchamber without the micropillar array is centered. The deviation of the cell distribution from the ideally uniform distribution in the microchamber with the micropillar array is suppressed by 63% compared with that in the microchamber without the micropillar array. The doubling time of the cells passed through the micropillar array did not change relative to that of normal N87 cells. This technique will be helpful for reproducing results in cellular research at the micro scale or for those using microfluidic devices.

This paper proposes a microfluidic device for screening molecules such as aptamers, antibodies, proteins, etc. for target cell-specific binding molecules. The discovery of cancer cell-specific binding molecules was the goal of this study. Its functions include filtering non-target cell-binding molecules, trapping molecules on the surface of target cells, washing away unbound molecules, and collecting target cell-specific binding molecules from target cells. These functions were effectively implemented by using our previously developed micro pillar arrays for cell homogeneous dispersion and pneumatic microvalves for tall microchannels. The device was also equipped with serially connected filter chambers in which non-target cells were cultured to reduce the molecules binding to non-target cells as much as possible. We evaluated the performance of the device using cancer cell lines (N87 cells as target cells and HeLa cells as non-target cells) and two fluorescent dye-labeled antibodies: Anti-human epidermal growth factor receptor 2 (anti-HER2) antibody that binds to target cells and anti-integrin antibody that binds to non-target cells. The results showed that the device could reduce anti-integrin antibodies to the detection limit of fluorescent measurement and collect anti-HER2 antibodies from the target cells.

In laparoscopic surgery, it is difficult to grasp large internal organs and drag it to make appropriate workspace by using conventional apparatus. Therefore, this paper proposes an assemblable mechanical hand for grasping the end of internal organs. This mechanical hand consists of the several units that can pass through a trocar, and can be assembled into a three fingered hand. Moreover, we developed a suction cup that can actively bend to fit the curved surface of the internal organs. The fingers equipped with the developed suction cups can grasp a pig liver without slippage.