This paper presents a superelastic alloy microgripper with integrated electromagnetic actuators and piezoelectric sensors. The design parameters for electromagnetic actuators in the microgripper are selected based on the sensitivity analysis using FEM analysis. For integration of miniature force sensors in the microgripper, the sensor design based on the piezoelectric polymer PVDF film and fabrication process are also presented. Electro discharge machining technology is employed to fabricate the microgripper structure made of superelastic NiTi alloy. The experimental setup is implemented to evaluate the performance of the fabricated force sensors and electromagnetic actuators integrated into the microgripper. Finally, results of finite element computer simulations for electromagnetic actuators and piezoelectric polymer sensors are compared with experimental results.
This paper describes the fabrication and characteristics of an ionic polymer-metal composite (IPMC) membrane-shaped micro-actuator and its application to the fabrication of a micro-pump. After fabricating two 8mm×8mm IPMC membrane-shaped actuators using a Nafion film, their displacements were measured. The fabricated IPMC membrane-shaped micro-actuators showed displacement of 14~27μ at the applied voltage ranging from 4VP-P to 10VP-P at 0.5Hz. Displacement of the IPMC actuator fabricated with a commercially available Nafion is large enough to make the IPMC actuator a membrane-shaped micro-actuator for fabricating an IPMC micro-pump. IPMC micro-pump was fabricated by assembling IPMC membrane-shaped micro-actuator and PDMS(polydimethylsiloxane) micro-channel together. PDMS micro-channel was designed to have nozzle/diffuser structures which make the fluids flow from inlet to outlet when the IPMC membrane-shaped micro-actuator is deflected up and down by the applied voltages. The measured flow rate of the fabricated IPMC micro-pump was about 9.9μℓ/min at 0.5Hz when the input voltage and duty ratio were 8V P-P and 50%, respectively. The test results illustrate that the fabricated IPMC micro-pump is suitable for pumping fluid through micro-channel on a PDMS substrate. Mechanical performances of beam-shaped and bridge-shaped conductive polymer actuator in aqueous solution and in solid electrolyte have been measured and analyzed. The optimum thickness of polypyrrole for the best bending performance is about 17-19 μm which has been polymerized at the current density of 5.4 μA/mm2 for 120 minutes. For the application of conductive polymer actuator to a micropump, silicon bulk micromachining process has been combined.
A quantitative analysis of drug release characteristics of polypyrrole (PPy) was performed for its application to a drug
delivery system (DDS). The incorporation of various chemical substances into the PPy and controlling its release with the externally applied voltage to the PPy are possible. A qualitative drug release characteristics of the PPy was first examined using an indicator, phenolred and then the quantitative analysis was performed using salicylate as a dopant. A drug release characteristics with time was thoroughly investigated while varying the electrode area, polymerization time, the applied voltage for drug release. Based on these quantitative results, a preliminary experiment was carried out to check the feasibility of the PPy applicable to the neuronal system. Experimental results show that a neurotransmitter was released from the PPy with the externally applied voltage and hence the PPy can be applicable in a neuronal system.
IPMC (Ionic Polymer Metal Composite) is a promising candidate actuator for bio-related applications mainly due to its biocompatibility, soft properties and operation in wet condition. The widely used and commercialized ion-exchange polymer film has limitation in thicknesses, but more various film thicknesses are required for extensive applications. Especially for the enhanced force as an actuator, acquisition of thick film is essential. Various ion-exchange polymer films with thickness of 0.4-1.2 mm have been prepared by casting of liquid ion-exchange polymer. As well, IPMC
actuators using cast ion-exchange polymer films have been fabricated and the basic mechanical characteristics such as stiffness, displacement and force were measured and analyzed. These results can be used for the optimized design of actuators for different applications.
We have developed the wireless tadpole robot that has simple geometry, driven by low voltage and the undulatory fin-motion using IPMC(Ionic Polymer Metal Composite) actuator. Behavior of TadRob is tested under various frequencies(1~8Hz) to find the correlation between actuator frequency and velocity of the robot. In addition, the robot velocity according to undulation motion and oscillation motion of the fin is compared to find the proper fin-motion to increase the efficiency of the robot. Also, steering capability is tested under variation of duty ratio. Based on experimental results, we can confirm that the velocity of TadRob can be controlled by changing frequency of input voltage and the steering angle can be increased with increasing the duty ratio.
Among many kinds of polymer materials, electronic conductive material, that is polypyrrole, shows potential possibility for bio-relate actuator materials. However, it may be an impediment for practical use in polypyrrole actuator that polypyrrole usually requires electrolyte solution for actuation. Our first research theme is focused on this problem solving. We have investigated many kinds of solid polymer electrolyes for the substitution of electrolyte solution. Our goals are to find the stable solid electrolyte in the air, to establish the reliable fabrication process of it and to apply it for micropump application. Besides actuators, the reduction and oxidation property of polypyrrole can be exploited for active drug delivery systems by the control of structural deformation of it. We have investigated this kind of new and bio-related possibility of polypyrrole. Shape memory alloy has another possibility in the biomedical field. Due to its inherent excellent advantages as actuator materials, it can be used for micro active intravascular catheter. We have developed thin tube type bending actuator using shape memory alloy and characterized its performance by in-vivo test.