We have studied on design, analysis, manufacture, control, measurement, and automation for creating unique and energy-efficient miniature mechanism, robot, and robotic factory.

> Holonomic mobile robot
> XYθ displacement sensor organized by multiple encoders
> Automation control of the Holonomic mobile robots by machine learning
> Capillary force gripper
> In-liquid manipulation by local flow generated by oscillation of pipette
> Automation of assembling for miniscule parts by image recognition
> SMA actuator
> Piezoelectric (PEA) actuator

Holonomic mobile robot

We are developing a compact and lightweight precision self-propelled mechanism for handling electronic components and small objects. This one consists of the XYθ stage which have three degrees of freedom using four piezoelectric actuators, connected to upper leg and lower leg. The motion is based on the principle of a scale insect, which moves in continuous fine motion by synchronizing the switching of the grounded leg by the vertical piezoelectric actuators with the expansion and contraction of XYθ stage.

By combining the expansion and contraction cycles of the four piezoelectric actuator and the switching of the grounded leg by the vertical piezoelectric actuators, translational and rotational movements are possible.

We are currently conducting research on automatic control of self-propelled mechanisms using machine learning. we have developed a system that performs pick-and-place of micro objects by image recognition and machine learning technology.

By working together, we aim to realize a micro-robot factory that features energy saving, low vibration, low floor space, and independent three-degree-of-freedom path generation.

Capillary force Gripper

Our laboratory is developing manipulation devices that use liquid bridging force, which is a departure from conventional object manipulation techniques. Liquid bridging force is an adhesion force generated by the surface tension of water and Laplace pressure. At the microscale, adhesion forces such as electrostatic forces are more dominant than gravity due to the scale effect. Therefore, when manipulating microscopic parts with an air nozzle or tweezers, this adhesion force causes them to stick to the tip of the nozzle. Liquid cross-linking forces are more dominant than adhesion forces and are therefore suitable for manipulating micro-parts.

Liquid bridging force has not only the advantage of force due to the scale effect, but also has the advantage of adhesion of liquid along the surface of the object to be operated, which is less affected by the surface shape and less likely to damage the object. We have developed a mechanism that continuously supplies liquid to the gripper tip using capillary action. This mechanism has successfully picked up parts of various shapes such as cubes, triangular pyramids, and semi-cylinders.

Multi-axial non-contact in situ micromanipulation by steady streaming around two oscillating cylinders on holonomic miniature robots

In the field of micromanipulation, an in situ three-axial rotation of a microscale object remains difficult to realize, with rotational resolution and repeatability remaining low. In this research, we describe the fundamental principle, properties, and experimental results of multi-axial non-contact in situ micromanipulation of an egg cell driven by steady streaming generated around an oscillating cylinder. A continuously oscillating cylinder generates the steady streaming that draws heterogeneous miniscule objects toward the cylinder. If it is trapped by an eddy near the tip of the cylinder, it continuously rotates around the vertical axis at a fixed point. If it is trapped by a swirl flow generated around the side of the cylinder, it rotates around the horizontal axis. We demonstrate that the conditions of the vertical and horizontal rotations are determined by two dimensionless numbers: Re and a/rc.

In our experiments, we obtained rotational resolutions of 0.05° and 0.11° and maximal angular velocities of 34.8°/s and 188°/s for the vertical and horizontal rotations for mouse egg cell, respectively.

We also developed unique micromanipulation methods using two oscillating pipettes attached to holonomic miniature robots. We successfully manipulated five degrees of freedom of the cell with the steady streaming. It can be applied in microfluidics, biomedical, and heterogeneous microassembly applications.

3D Helical Micromixer Fabricated by Micro Lost-Wax Casting

Joint research with Ota lab. 2019-2020

Micromixers produced by micro fabrication techniques have attracted attention for micro total analysis systems and lab-on-a-chip applications in point-of-care testing. However, the fabrication and setup of micromixers have become more complex and more difficult. Considering the practical use of micromixers in medical and industrial applications, their designs can be simplified while maintaining high mixing efficiency. Rapid prototyping, represented by 3D printing having micro-scale resolutions, is one promising technology to replace conventional fabrication methods such as soft lithography.

Here, a 3D helical micromixer fabricated by micro-scale lost-wax casting is reported. The molds for lost-wax casting are fabricated by fine 3D printing of a hard wax resin which can be removed from a polydimethylsiloxane block just by heating and washing with water, and a fine and smooth structure is realized. The optimized helical micromixer fabricated by lost-wax casting promotes mixing efficiency compared with other micromixers. In addition, a monolithic microchannel having the helical 3D bridge structure is presented in this study. The demonstration is an important advancement toward the industrial applications of micromixers fabricated by micro-scale 3D printing. The ability to fabricate complex structures can simply lead to the creation of more sophisticated mixers in the future.

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