Sumito Nagasawa

Design of electrostatic adhesion device using the flexible electrodes

This paper presents a fabrication method of electrostatic adhesion device using flexible electrodes. When an electric charge is stored in the bipolar plate of a capacitor, an electrostatic force acts. We perform adhesion to a wall surface using this electrostatic force. Using the electrostatic force, electrostatic adhesion force is controlled by the electricity. The flexible electrodes are created by spraying a solution containing dispersed carbon black onto a silicon rubber. Flexibility of the device can avoid damage to its own and adapt to a variety of wall surface shapes. In experiments, two kinds of device surface structures were created. One is just flat and the other is pillar arrays. The pillar arrays structure was adopted from the viewpoint of biomimetic. Electrostatic adhesion force of these structures was measured with shear and tensile testing machines.

Self-beating gel pump powered by chemical energy

Many examples of microfluidic systems have been studied in various fields. Normally, micropumps in microfluidic systems are powered by electricity or heat generated from electric energy and the actuation is controlled by on-off switching of external inputs. Herein we report a novel autonomous flow control inside microfluidic channels powered by self-oscillating gels without external control devices. Self-oscillating gels exhibit a volume oscillation driven by the oscillatory Belousov-Zhabotinsky (BZ) reaction. Our approach greatly simplifies the microfluidic system construction because there is no need for the electric wiring and source. In this paper, we first demonstrate a directional fluid pumping within microfluidic channels and a directional flow rate was 0.02 μL/min utilizing self-oscillating gels. This self-actuated pump could serve as a new framework for microfluidic devices.

Displacement magnification of gel actuator using pNIPAAm-SU8 hybrid structure

In this paper, a fabrication method for a hybrid structure of the poly-N-Isopropylacrylamide (pNIPAAm) gel as a soft material and the SU-8 as a solid material is proposed. This pNIPAAm-SU8 hybrid structure can be applied to various applications such as gel actuators. These hybrid structures have a serious problem that it is easily broken by the difference of swelling rate. Our proposed hybrid structure was not broken though repeating swelling-shrinking states for 10 or more times. A small displacement of the gel is occurred by the phase transition, then it is magnified by combining with the SU-8 solid structure. We demonstrated that the expanded tip displacement of the SU-8 solid structure reached 145μm.

Trajectory control of MEMS falling object fabricated by SU-8 multilayer structure

In this paper we propose a trajectory control method for a MEMS falling object as shown in Figure 1. The MEMS falling object is consisted of two units, an autorotation part and a non-rotation part. The autorotation part keeps its attitude stable with the gyro-effect of the autorotation phenomenon. The non-rotation part keeps a non-rotation state by using the air breaking boards. This non-rotation part controls its falling trajectory and the scattering region. By using large falling objects, aerodynamics of the falling object was characterized, e.g. falling speed, rotational speed, etc. Then the MEMS falling object was designed considering with this aerodynamics. The MEMS falling object was fabricated with a method of the SU-8 multi-layer structure. A MEMS autorotation part whose wing length is 6mm in diameter rotates at 4,800 rpm in the wind-tunnel successfully.

Design of self-moving gel driven by chemical energy

In this paper, we report the autonomous driving actuator like living organisms. Many researchers have developed the biomimetic actuators and applied many kinds of stimuli-responsive polymers and gels to the soft actuators. Generally, robots are composed of various parts and require the external device such as thermal energy or electricity. On the other hand, many living organisms can generate an autonomous rhythm cycle phenomena without external stimuli, such as the heartbeats, circadian rhythm and so on. In this study, we proposed an autonomous gel actuator similar to the living organism, using self-oscillating polymer gels (BZ gels). The BZ gel is an intelligent material that undergoes autonomous swelling-deswelling oscillations without external stimuli. We aimed at the autonomous locomotion in one direction as a new actuator. Herein, we report fabrication of the self-oscillation gels with the asymmetric shapes and the movement experiment. We have succeeded in observing that the gel could walk autonomously in one direction.