Mitsuhiro Horade

A microfluidic device for quantitative analysis of chemoattraction in plants

To precisely quantitate the effect of chemoattractants on directional pollen tube growth, a new microdevice was developed. Torenia fournieri pollen tubes, which generally grow freely on agarose medium, were funneled through a narrow flow channel that splits into a T-shaped channel leading to two reservoirs. The main channel was thus divided in two so that pollen tubes could choose their growth in either the left or right direction. Liquid solution or plant tissues were loaded into the reservoir, and diffusible molecules from the materials gradually spread in the narrow channel, leading to a concentration gradient. When egg-cell containing ovules were placed in one reservoir, pollen tubes grew selectively in that direction, suggesting that materials secreted from the ovules attracted the pollen tubes. Furthermore, UV-irradiation of female gametophytes in ovules decreased their ability to attract pollen tube growth. These results suggest that this novel device provides a unique platform for screening materials that may attract pollen tubes and for quantitatively analyzing the chemical features of attractants.

Microneedle fabrication using the plane pattern to cross-section transfer method

In this paper, microneedle fabrication using the PCT (plane pattern to cross-section transfer) method is summarized. Three types of microneedle array have been developed: the single-tip, quadruplet, and hollow microneedle arrays. A brief introduction to the fabrication process using PCT and detailed design concepts for optimizing the fabrication steps for shape improvement of the three types of microneedle are provided. The microneedle structures have controllable angled sidewalls, exhibiting an extraordinarily geometrical level of accuracy compared to what is achieved using other existing fabrication methods based on deep x-ray lithography by synchrotron radiation. Furthermore, the improvements reported in this work as compared to the results from the existing methods are: sharper tips for the single-tip microneedles, strength improvement for the quadruplet microneedles, and cost reduction for the hollow microneedles. Each type of microneedle was designed to serve a different biomedical need.

An On-Chip RBC Deformability Checker Significantly Improves Velocity-Deformation Correlation

An on-chip deformability checker is proposed to improve the velocity–deformation correlation for red blood cell (RBC) evaluation. RBC deformability has been found related to human diseases, and can be evaluated based on RBC velocity through a microfluidic constriction as in conventional approaches. The correlation between transit velocity and amount of deformation provides statistical information of RBC deformability. However, such correlations are usually only moderate, or even weak, in practical evaluations due to limited range of RBC deformation. To solve this issue, we implemented three constrictions of different width in the proposed checker, so that three different deformation regions can be applied to RBCs. By considering cell responses from the three regions as a whole, we practically extend the range of cell deformation in the evaluation, and could resolve the issue about the limited range of RBC deformation. RBCs from five volunteer subjects were tested using the proposed checker. The results show that the correlation between cell deformation and transit velocity is significantly improved by the proposed deformability checker. The absolute values of the correlation coefficients are increased from an average of 0.54 to 0.92. The effects of cell size, shape and orientation to the evaluation are discussed according to the experimental results. The proposed checker is expected to be useful for RBC evaluation in medical practices.

Piezo-actuated parallel mechanism for biological cell release at high speed

In this paper, a dynamic releasing approach is proposed for high-speed biological cell manipulation. A compact parallel mechanism for grasping and releasing microobjects is used to generate controllable vibration to overcome the strong adhesion forces between the end effector and the manipulated object. To reach the required acceleration of the end effector, which is necessary for the detachment of the target object by overcoming adhesion forces, vibration in the end effector is generated by applying sinusoidal voltage to the PZT actuator of the parallel mechanism. For the necessary acceleration, we focus on the possible range of the frequency of the PZT-actuator-induced vibration, while minimizing the amplitude of the vibration (14 nm) to achieve precise positioning. The effect of the air and liquid environments on the required vibration frequency for successful release is investigated. For the first time, release results of microbeads and biological cells are compared. Release of the biological cells with 100 % success rate suggests that the proposed active release method is an appropriate solution for adhered biological cells during the release task.

Releasing and accurate placing of adhered micro-objects using high speed motion of end effector

This paper presents an active release method of microobject for the improvement of the position accuracy after releasing by using 3D high speed motions of an end effector. In the micro manipulation, the release task is the challenge work due to adhesion forces. To overcome the adhesion force and to place microobject accurately on the desired location, in this paper, we propose a high speed motion by analyzing dynamic model of manipulated end effector and attached microbeads. Two fingered microhand driven by DC motors and PZT actuators is utilized for this paper. Parallel mecahnism with three PZT actuators was used for making 3D motion at high speed. To generatge high acceleration of end effector, many researchers applied simple vibration by using an additional PZT actuator. In our research, 3D high speed motion with large amplitude was achieved by only using a compacted parallel mechanism. To verify the advantage of the proposed motion, we compare five motions, 1D motions (X, Y, and Z direction) and circular motions (clockwise and counterclockwise direction), by changing the frequency and moving distance of the end effector. From these results of experiments, we conclude that the circular motion can detach microobjects with high placing accuracy after release.

Releasing of adhered micro-objects using local stream generated by high speed motion of end effector

This paper presents a contactless release method of microobject using local stream generaged by high speed motions of an end effector. In the micro manipulation, the release task is a challenge work due to adhesion forces. To overcome the adhesion force and to place microobject on the desired location, in this paper, we apply local stream using high speed motion controlled by a parallel link. Two fingered microhand driven by DC motors and PZT actuators is utilized for this paper. Parallel mecahnism with three PZT actuators was used for making 3D motion at high speed. To generatge high acceleration of end effector, many researchers applied simple vibration by using an additional PZT actuator. In our research, 3D high speed motion with large amplitude was achieved by only using a compacted parallel mechanism. Using local stream generated by the high speed motion of the right effector, 55μm microbeads attached to the left end effector are released. To verify the placing accuracy by the proposed method, we compare four motions, 1D motions (X and Z direction) and circular motions (clockwise and counterclockwise direction), by analyzing the trajectory of the microbeads after release. From these results of experiment, we conclude that the circular motion can detach microobjects on desired position after release.

Development of an optimum end-effector with a nano-scale uneven surface for non-adhesion cell manipulation using a micro-manipulator

In order to realize effective micro-manipulation using a micro-manipulator system, an optimum end-effector is proposed. Cell-manipulation experiments using mouse fibroblast cells are conducted, and the usability of the proposed end-effector is confirmed. A key advantage of the micro-manipulator is high-accuracy, high-speed 3D micro- and nano-scale positioning. Micro-manipulation has often been used in research involving biological cells. However, there are two important concerns with the micro-manipulator system: gripping efficiency and the release of gripped objects. When it is not possible to grip a micro-object, such as a cell, near its center, the object may be dropped during manipulation. Since the acquisition of exact position information for a micro-object in the vertical direction is difficult using a microscope, the gripping efficiency of the end-effector should be improved. Therefore, technical skill or operational support is required. Since, on the micro-scale, surface forces such as the adsorption force are greater than body forces, such as the gravitational force, the adhesion force between the end-effector and the object is strong. Therefore, manipulation techniques without adhesion are required for placed an object at an arbitrary position. In the present study, we consider direct physical contact between the end-effector and objects. First, the design and materials of the end-effector for micro-scale manipulation were optimized, and an end-effector with an optimum shape to increase the grip force was fabricated. Second, the surface of the end-effector tip was made uneven, and the adhesion force from increasing on the micro-scale was prevented. When an end-effector with an uneven surface was used, release without adhesion was successful 85.0% of the time. On the other hand, when an end-effector without an uneven surface was used, release without adhesion was successful 6.25% of the time. Therefore, the superiority of a structure with an uneven surface was demonstrated, and high-accuracy cell manipulation without sliding during handling and without adhesion was performed successfully.

Keyframe Selection Framework Based on Visual and Excitement Features for Lifelog Image Sequences

Keyframe selection is the process of finding a set of representative frames from an image sequence. We aim to achieve an automatic keyframe selection. The main problem is that the accuracy of keyframe selection is highly subjective to each particular user. To deal with this problem, we propose a VIEMO keyframe selection framework based on visual and excitement features that consists of two integrated modules, namely; event segmentation and keyframe selection. Firstly, scene change detection algorithm was applied for an event segmentation. Later, visual features which are contrast, color variance, sharpness, noise and saliency along with excitement features from a biosensor are used to filter keyframe that closely matches with user selection keyframe. Two different fusion scheme which are flat and hierarchical fusion were also investigated. To evaluate the quality of keyframe from the proposed method, we present an evaluation techniques which grades the quality of the keyframe automatically. Even when the keyframe does not exactly match with the keyframe selected by the user, the degree of acceptance calculated from visual similarity is provided. Experimental results showed that keyframe selection using only visual features yielded an acceptance rate of

Novel ultra-lightweight and High-resolution MEMS X-ray optics for space astronomy

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