Kouichi Itoigawa

High-speed separation system of randomly suspended single living cells by laser trap and dielectrophoresis

We developed a new system for random separation of a single microorganism, such as a living cell and a microbe, in the microfluidic device under the microscope by integrating the laser‐trapping force and dielectrophoretic (DEP) force. An arbitrarily selected single microbe could be isolated in a microchannel, despite the presence of a large number of microbes in solution. Once the target microbe is trapped at the focal point of the laser, we can easily realize exclusion of excess microbes around the target by controlling the electric field, while keeping the target trapped by the laser at the focal point. To realize an efficient separation system, we proposed a new separation cell and produced it by microfabrication. Flow speed in the microchannel is adjusted and balanced to realize high‐speed and high‐purity extraction of the target. Some preliminary experiments are conducted to show the effectiveness. The target is trapped by the laser, transported, and is taken out from the extraction port. Total separation time is less than 20 s. Our method is extremely useful in the pure cultivation of the cell and will be a promising method for biologists in screening useful microbes.

Integrated microendeffector for micromanipulation

Micromanipulation is needed for assembly and maintenance of micromachines and their parts. If the handled objects are miniaturized, interactive forces, such as the van der Waals force, surface tension force, and electrostatic force between microobjects and gripper surface become dominant in the air, and they act as adhesive forces. We cannot neglect such adhesive forces in micromanipulation. Considering the physical phenomena in the microworld, we propose reduction methods for adhesive forces. Surface roughness of the endeffector surface is effective to reduce the van der Waals force. We propose making the micropyramids on the endeffector surface by micromachining techniques. We designed and made a prototype of the microgripper with a microendeffector, the gripping surface of which is formed to have several micropyramids. Experimental results show effectiveness of the micropyramids for reduction of the adhesive force. We also made a semiconductor strain gauge at the end of the microendeffector for grasping force measurement. Both micropyramids and integrated piezoresistive force sensor are fabricated on the microendeffector by the micromachining techniques. Performance of this force sensor is shown.

High speed random separation of microobject in microchip by laser manipulator and dielectrophoresis

We developed a new system for high speed random separation of a microobject, such as a microbe, in a microfluidic device by optical radiation pressure and dielectrophoretic force control under a microscope. An arbitrary single microbe can be isolated speedily in a microchannel, even though there are a large number of these microbes in solution. Once the target microbe is trapped at the focal point of the laser manipulator, we can easily realize exclusion of excess microbes by controlling the electric field, while keeping the target trapped at the focal point. To realize an efficient separation system, we made a new separation cell by microfabrication. We show experimental results on our system. We also propose indirect manipulation methods by the micro-tools to avoid direct laser radiation to the target. Some preliminary experiments are conducted to show the effectiveness. Our method is extremely useful in the pure cultivation of the targeted microbe and will be a promising method for biologists in discovering a new microbe or for bio-remediation.

3D viewpoint selection and bilateral control for bio-micromanipulation

A need has arisen to manipulate a small biological object, such as an embryo, cell, and microbe. Bio-micromanipulation is important for biology and the bioengineering field. However, it is very difficult, since the object is very small, kept in liquid, and observed by an optical microscope. The image of the microscope is two dimensional, so it is hard to manipulate the target in 3D space. The object is fragile, so it is hard to manipulate safely. To improve the manipulation works, the authors propose the viewpoint selection method in VR space, and a bilateral control system to improve manipulation of the micro object under the microscope.

Structure design of micro touch sensor array

Abstract The micro touch sensor array is fabricated by Ti substrate and PZT thin-film. PZT thin-film is synthesized by hydrothermal method and used as both micro sensor and micro actuator. Micro touch sensor array is not only simple to suit for miniaturization, but also robust against the disturbance. It will have numerous areas of application instead of conventional switch based on the mechanical contact. In this study, structure design of micro touch sensor array is presented. The main focus of structure design is on improving the sensitivity of micro touch sensor array. A mathematical model, which is used to optimize structure design of micro touch sensor array, is derived. According to cantilever beam theory, the frequency response to electric output of micro touch sensor unit has been discussed. The effects of changing physical parameters such as the location of the electrodes of PZT actuation and sense layer, and the length of the electrodes of PZT layers are studied. Based on the maximum output of micro touch sensor unit, the optimal structure has been obtained from both sides of analysis and experiment.

Three-dimensional bio-micromanipulation under the microscope

We develop a new micromanipulation system for anatomical operation of the micro-object such as an embryo, cell, and microbe. The image of the microscope is two-dimensional, so it is hard to manipulate the target in the 3D space. To improve the manipulation work, we proposed a 3D bio-micromanipulation system combined with a virtual reality (VR) space. We propose a 3D object modeling method for presenting 3D visual information to the operator and improve the operation environment. In this system, we still have difficulty in changing the orientation of the microscopic object by manipulating a mechanical manipulator. The bio-aligner proposed is a micro device for the posture control of an object. We develop a 2D bio-aligner by microfabrication. Here we show its fabrication process and a basic rotating experiment with yeast cells.

Micro force sensor for intravascular neurosurgery and in vivo experiment

Catheter is one of the medical tools for endovascular surgeries, and it is frequently used for neurosurgical operations. There is, however, a problem that doctors operate a catheter without any force information during their operation, and this problem causes fatigue of doctors. To solve this problem, we propose a micro force sensor for intravascular neurosurgery. This micro force sensor can be installed on the tip of the catheter. The diameter of this sensor is 1.5 mm and length is 12 mm. Using this micro force sensor, we can measure the contact force between the catheter and blood vessels. To express the contact force between catheter and blood vessels is very effective for safe operation. In this paper, we show the structure of the micro force sensor and its characteristics, and also we present the result of an in vivo experiment.

Micro tri-axial force sensor for 3D bio-micromanipulation

It is important to manipulate a biological small object, such as a cell and embryo. Three-dimensional high speed micromanipulation is needed as a fundamental technology for biology and bio-engineering application. In this paper, we focus on the contact type micromanipulation in the liquid. We designed and made a contact type micromanipulation system which has a 3-DOF narrow range positioning system on a 3-DOF wide range positioning system. We developed a micro tri-axial force sensor which can be installed near the tip of the end effector. Performance of this micro-force sensor is presented.

3D micromanipulation system under microscope

It is important to be able to manipulate a biological small object, such as a cell and embryo. Three-dimensional high speed micromanipulation is needed as a fundamental technology for bio-science and bio engineering application. In this paper, we focus on the contact type micromanipulation in the liquid, and introduce new methods to improve operability and working efficiency.

Micro force sensor for intravascular neurosurgery

Minimum invasive surgery using intravascular surgical tools is getting greater attention in the medical field. This technique allows us to reduce physical pain for patients. For example, a catheter is one of the medical tools for endovascular surgeries. The catheter is frequently used for neurosurgical operations. We propose a new type of force sensor for intravascular neurosurgery. This micro force sensor can be installed on the tip of the catheter. We developed a prototype micro force sensor whose diameter is 1.6 mm and length is 12 mm. Using this micro force sensor, we can measure the contact force between the catheter and blood vessels. It is possible to push the blood vessel wall hard when operators use the catheter. So, to express the contact force between catheter and blood vessels is very important for safe operation. In this paper, we show the structure of the micro force sensor and its characteristics.