Recent development in mechatronics, what kind, why beneficial, what are those material, what brand. In depth later
Composite has been used widely in many areas. It has since gained more popularity because of its unique properties compare to normal materials. In recent year, there has been many research conducted to study about useful composites polymer, one of which is IPMC. IPMC which stands for Ionic Polymer Metal Composite, has been used mainly in microrobotics and bio robotics areas. The main discussion topic in this articles review will be about IPMC, its the usage and manufacturing techniques.
IPMC is one of material that might be bent when electricity goes through it. The bending magnitude can be easily controlled by how big electricity is supplied to the specimen. It also able to work in wet environment and the operation of this material is relatively quiet. Also, the bending mechanism is simple that this material can be applied to many complicated machine or robots to perform many complicated things. The way IPMC work is that when electricity goes through it, positively charged ion will go to one side, and negatively charged ion will go to the other side, thus creating a concentration on each side and bend.
There are a lot of available commercially produced IPMC, some of them are Nafion (DuPont) and Flemion (Asahi glass), these material is sold in a form of thin membranes (100-300) microns thickness. IPMC is essentially a material that has 2 electrodes on both sides so that electricity can go through it.
Research conducted by D.Pugal et.al focuses on manufacturing different shapes of IPMC and how to make it bendable in many direction, since so far IPMC might only be bended in one direction only. There are a couple methods that these researchers use to achieve such properties, one of which is using hot press method.
First, Ionic polymer beads is processed using a hot press machine to produce a certain shape like fish fin, cube, rod, etc. Now the next step is to electroplating those specimens. They are trying to modified the pattern of electrodes that will be applied to the surface of ionic polymer, by photolithography or laser printing. Such methods are used to allow multiple bending direction of the ionic polymer. The researchers are able to modify the bending motion of the IPMC by altering the electrodes on the surface, and enable it to bend in many directions like twisting.
As it has been mentioned before, one problem with using IPMC is that it has been produced largely in a very thin layer or membranes. Many researchers have been trying to develop a way to produce a thicker and customable IPMC. Two of them are Kwang K. and Mohsen Shahinpoor M. They are trying to develop a thicker IPMC membranes that may be applied to many other areas. There are many ways to manufacture thicker membrane, two of them are solution casting method and multi layering technique. Multi layering technique simply means layering multiple IPMC to increase the thickness while solution casting means composite will be manufactured from a liquid form of ionic polymer and pour it into a cast.
Currently, there are three types of available ionic polymer or raw material for IPMC in the market, which are powder, solid, and liquid Nafion (DuPont). All three are essentially the same but are in different form. Each of those is used depending on what kind of product or application that it is going to be used in.
In this research, liquid Nafion was used to create a thick membrane. Liquid is chosen because it is easy to work with, and compare to the powder form, liquid Nafion has higher yield strength. Liquid Nafion is composed of 10% Nafion and 90% water/alcohol based solvent. The manufacturing process start from pouring liquid Nafion to Pyrex glass and heat it to 70 degrees, when it starts to solidify, the temperature is further increased to 150 for curing process. The last step is to electroplate the solid Nafion with platinum.
Article 3 – Tadpole Robot
One application of IPMC is in aquatic robotics, because of its waterproof properties. Research conducted by Kim B. et.al, aims to use thin membrane IPMC as a tadpole robot fin, and investigate the effectiveness of using such material in aquatic robot.
They start by cutting the membranes to tail shape and attached it as an extension of the fin of the tadpole. The fin itself is made of 2 materials which are PDMS polymer and Pet film. The IPMC fin extension was then attached to those fin which will bend depending on how big the electricity applied thus create thrust.
The result is actually quite surprising. They found that the speed of tadpole movement on the water is 23.6 mm/s with PDMS polymer and 13.5 with PET fin. Fin made of one material could provide almost double a speed of movement of fin made of another material. This also shows that the bending magnitude provided by IPMC is strong enough to actually provide movement to the tadpole dummy.
Article 4 – Fish Robot
Another application of IPMC in the area of underwater robotic is robotic fish. Similar to the research that has been conducted above, a group of researchers, Chen Z., Shatara S., and Tan X. use IPMC as a fish fin, and investigate the maneuver of the fish with IPMC fin attached to the plastic fin. However, in this experiment, they are focusing on the steady state speed of the fish instead of just comparing which material might perform best. The methodology is almost the same as the tadpole robot research, they both are using IPMC as fin, and using laser displacement sensor to obtain maneuvering speed.
To begin with, desired shape and size of extension fin is attached to the passive fin on the body of the fish. Then square wave voltage with amplitude of 3.3V is applied. The fish robot is then tested inside a small aquarium, and laser sensor will record the displacement, and using time travel of the robot, speed can be calculated.
Article 5 – Jellyfish Robot
One last application of IPMC that will be reviewed is jellyfish robot. Jellyfish is one of animal that moves by using its whole body. When the body contract it pushes water out of its body, allowing jellyfish to moves in one direction. Since jellyfish does not have any other body part to create force to move, it periodically contract its body to create thrust and move vertically. The locomotion of jellyfish is kind of similar to jet propulsion, the force is coming out from one opening, and pushes the body.
Experiment done by Oh I., and Yeom S., aims to compare the movement of jellyfish exposed to sinusoidal and bio-inspired signal. Bio-inspired signal is slightly different from sinusoidal signal. Bio-inspired signal is a periodic signal just like sinusoidal but based on the ratio of pulsating and recovery process of jellyfish body, in this case is 3:7. It believed that feeding bio-inspired signal to the robot might yield to a very similar and close movement of the robot to a real jellyfish.
IPMC will be used mostly for the body for the robot. Thermal treatment was done to the IPMC to get a desirable shape of jellyfish body parts. There are two main body parts that is produced with IPMC, one is legs, and another one is skirt. Both are manufactured from IPMC and have undergo a thermal process to shape it, and the for skirt part, they are using cellophane paper to cover the IPMC to prevent a water damage.
Similar to the experiment that has been done by other researchers, they also use displacement sensor to record a vertical displacement of the robot. The result is that they found bio-inspired signal that has been applied to the IPMC makes the movement of robot very similar to the real jellyfish, and also much larger displacement was achieved.
It turned out that the robot that was exposed by bio-inspired signal
Chen, Z., Shatara, S., & Tan, X. (2010). Modeling of Biomimetic Robotic Fish Propelled by An Ionic Polymer–Metal Composite Caudal Fin. IEEE/ASME Transactions on Mechatronics IEEE/ASME Trans. Mechatron., 15(3), 448-459. doi:10.1109/tmech.2009.2027812
Kim, K., & Shahinpoor, M. (2002). A novel method of manufacturing three-dimensional ionic polymer–metal composites (IPMCs) biomimetic sensors, actuators and artificial muscles. Polymer, 43(3), 797-802. doi:10.1016/s0032-3861(01)00648-6
Kim, K. J., & Shahinpoor, M. (2003). Ionic polymer metal composites: II. Manufacturing techniques. Smart Mater. Struct. Smart Materials and Structures, 12(1), 65-79. doi:10.1088/0964-1726/12/1/308
Pugal, D., Kim, S. J., Kim, K. J., & Leang, K. K. (2010). IPMC: Recent progress in modeling, manufacturing, and new applications. Electroactive Polymer Actuators and Devices (EAPAD) 2010, 1-10. doi:10.1117/12.848281
Yeom, S., & Oh, I. (2009, June 03). A biomimetic jellyfish robot based on ionic polymer metal composite actuators. Smart Mater. Struct. Smart Materials and Structures, 18(8), 1-10. doi:10.1088/0964-1726/18/8/085002
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