Koji Ikuta

Safety Evaluation Method of Design and Control for Human-Care Robots:

We propose the worlds first general method of evaluating safety for human-care robots. In the case of a careless collision between a robot and a human, impact force and impact stress are chosen as evaluation measures, and a danger-index is defined to quantitatively evaluate the effectiveness of each safety strategy used for design and control. As a result, this proposed method allows us to assess the contribution of each safety strategy to the overall safety performance of a human-care robot. In addition, a new type of three-dimensional robot simulation system for danger evaluation is constructed on a PC. The system simplifies the danger evaluation of both the design and control of various types of human-care robots to quantify the effectiveness of various safety strategies.

Submicron manipulation tools driven by light in a liquid

Optically driven micromanipulators with submicron probe tips are proposed and developed by using two-photon microstereolithography. The micromanipulators are worked by maneuvering their movable component with a focused laser beam, and an actual pair of microtweezers was opened and shut precisely. We also propose an effective method of controlling movable micromachines with great freedom of movement. In this method, a dot is attached to a movable component for trapping and driving it by a single laser beam. A microneedle was induced to perform several types of motion such as rotation and translation. The optically driven micromanipulators are useful for bionanotechnology applications that require work to be done in aqueous solutions.

Force-controllable, optically driven micromachines fabricated by single-step two-photon microstereolithography

We have fabricated optically driven micromechanisms and demonstrated their motion under optical force. All of the movable microcomponents are directly fabricated through an assembly-free process using the high-speed scanning of a femtosecond laser focused inside a photocurable resin. Since these movable micromachines are made from photocurable resin transparent to visible and near-infrared light, they can be driven by the force of optical trapping. We demonstrate a simple, versatile method for driving movable micromachines. Part of the movable component is optically trapped by a single laser beam and manipulated according to the desired trajectory. Various types of motion, including rotation and swinging are demonstrated. In addition, the optically driven micromachines can be force-controlled to femtonewton order by adjusting the position trapped by the laser beam. We demonstrated the femtonewton order force-controllable swing motion of micromanipulators. A microturbine was rotated by circular scanning of a trapping laser beam in a liquid. Such force-controllable optically driven micromachines are promising manipulation tools for biomolecules such as DNA and protein.

Three-dimensional microfabrication by use of single-photon-absorbed polymerization

We developed a promising method to fabricate three-dimensional microstructures by using single-photon-absorbed polymerization confined to the vicinity of a tightly focused spot. This localized polymerization is based on the nonlinear response of the photopolymerizable resin to optical intensity with sufficiently low exposure. The nonlinear response was verified by measuring polymerization exotherm at different light intensities. The proposed method enables us to make even movable microstructures without any of the supporting parts or sacrificial layers normally required with conventional micromachining. In the experiment reported here, we fabricated a microgear with an external diameter of 47 μm and an attached shaft.

Development of remote microsurgery robot and new surgical procedure for deep and narrow space

We developed both new operation procedure and new robot system for remote micro surgery at deep and narrow space of human body. This system allows us to operate a difficult microsurgery that conventional method cannot be achieved. Our system consists of flexible stem and slave micro manipulators which can enter deep site such as brain through narrow channel. The macro motion of master manipulator can be converted into miniature motion of the slave microsurgery manipulator with five degrees of freedom in 3 mm diameter. This system has been taking advantage of flexible catheter and decoupled micro manipulator invented by Ikuta. Total performance was verified by animal experiment.

Micro concentrator with opto-sense micro reactor for biochemical IC chip family. 3D composite structure and experimental verification

The concentration process is an indispensable in various chemical operations for both detection and purification. However, little research to miniaturize it have been done so far. In this paper, the world-first micro concentrator chip using ultrafiltration membrane for biochemical micro devices is developed. The micro concentrator chip consists of ultrafiltration membrane to filter molecule and a micro reactor with optical sensor to detect progress of biochemical reaction optically. Basic performance as a concentrator and real-time monitoring in-chip protein synthesis are demonstrated successfully. Another important feature of this chip is fabrication method. The Micro Stereo Lithography (IH Process) being developed in authors laboratory enable to make the chip three dimensionally without any mask process. Both the packaging difficulty and leakage problem are eliminated completely.

Safety-optimizing method of human-care robot design and control

We propose a safety-optimizing method for safety strategies of human-care robots using our danger evaluation method. First, various safety evaluation methods are discussed, and an optimizing method of safety design is proposed. Second, we make a comparative study of two general safety control methods, and then a method of optimizing robot control is proposed. These proposed methods enable us to optimally distribute cost among several safety strategies, and to derive suitable approaching motion of a multi-link manipulator to a human. The validity and effectiveness of these methods are demonstrated by numerical analysis. As a result, the design and control to increase safety are successfully obtained.

Hyper-finger for Remote Minimally Invasive Surgery in Deep Area

A new robotic system named Hyper Finger for minimally invasive surgery in deep organs has been developed. The finger size of the latest version is 10 mm and the entire system is much smaller and lighter, and can be set up on a camera tripod. This is one of the smallest master-slave robots in medicine. Each finger has nine degrees of freedom and several unique mechanisms are employed to solve the fundamental issues of conventional wire drive manipulators. The new concept and system were verified successfully by in-vivo remote minimally invasive surgery. Further improvements of the system toward a clinical version are now underway.

Multi-polymer microstereolithography for hybrid opto-MEMS

We have developed a novel microstereolithography method for producing a hybrid structure using multiple photocurable polymers. This method, termed the Multi-polymer IH process, has the potential to provide us with various functional microdevices, such as actuators, sensors and optical devices. The microdevices are produced by combining the diverse properties of different photocurable polymers. To verify the basic performance of our process, several optical waveguides were made with two kinds of photocurable polymers having different refractive indexes. By combining the optical, electrical and mechanical properties of photocurable polymers, this process should advance Polymer MEMS technology and make a substantial contribution to microoptics and microchemical devices for BioMEMS.

Fabrication of freely movable microstructures by using two-photon three-dimensional microfabrication

We report the latest 3D fabrication system based on two- photon-initiated polymerization. In two-photon 3D microfabrication, 3D microstructures can be made by scanning an ultrashort-pulsed near-IR laser beam inside liquid photopolymer without layer-by-layer process. Our current system has achieved lateral and depth resolutions of 0.2 micrometers and 0.28 micrometers , respectively. Movable micromechanisms, i.e., microgears, can be also fabricated without any use of supporting parts. For instance, a microgear with an attached shaft was successfully fabricated. Rotation of a microgear was verified during washing out unsolidified photopolymer.