A water strider is a small aquatic insect that is common in lakes, ponds and wetlands, about 8 to 20 mm long. The water strider has bristles smaller than 3 microns on each leg. In the bristle, there are grooves that form helical nano-structure on the surface. The air in the grooves forms the air cushion. It prevents the fluid from entering into and allows it to walk freely on the water without wetting its legs. Such structure of the water strider has many advantages like having less resistance, high stability, high mobility at waking on the water, and high floating ability on the water.
The purpose of this study is to develop a bio-mimic water strider robot that is small in volume, light in weight and reacts quickly on the surface using the super hydrophobic property of its leg. In order to achieve this purpose, we designed the artificial leg structures with hydrophobicity and fabricated the legs and bodies by using 3D printing, which is getting popular nowadays. To add super hydrophobic properties to fabricated legs, super hydrophobic coating was applied.
The results of this study are summarized as follows.
1) Based on knowledge about the super hydrophobic structure of legs of the water strider, we designed 3 kinds of leg structures like wire leg with a plastic round disc foot, wire leg with specified angle at bottom, PLA leg thru 3D printing. From the experiment of bearing capacity against water, we found that the PLA structure using 3D printing has the highest bearing capacity.
2) Three kinds of leg structures using with 3D printing such as Cylindrical leg, rectangular leg, and thorny leg structure were designed and fabricated. The results of comparing the bearing capacity about 3 kinds show that the thorny leg structure has highest bearing capacity, and it was confirmed that the larger the surface area can make the higher bearing capacity.
3) In the comparison of length of legs made with 3D printing, 85mm showed the highest bearing capacity, In the comparative experiments with the filling density, it was found that the legs made with 30% filler density had the greatest bearing capacity.
4) It has been confirmed that the super hydrophobic coating on the thorny leg structure has more than double of the bearing capacity.
5) We have analyzed the driving method of the water strider, and found out that the motor drive method using two wings is a useful method thru the several experiments
The water strider robots designed and fabricated in this study moves fast and stably on the water with high bearing capacity. Therefore, we are confident that our robot structure can be used for some applications like detecting humidity and harmful gases in the wet areas, because some sensors can be equipped.
However, there is a problem that the power supply must be supplied by wire and the wireless control method which can be moved in various directions is applied. So, I think it is necessary to further research on ways to improve the utilization of the robots.