image: (a) The system consisted of six parts as follows: (1) a force transducer; (2) a BAP; (3) a fixture; (4) a high-speed camera; (5) a pool; and (6) a data acquisition system. (b) Photo of the BAP. (c) Schematic illustration of the BAP. The base of the L-shape appropriated part of the femur of the water strider’s leg. (d) The BAP can repel water and it is not caught by the meniscus when the water surface is close to the BAP. (e) If the BAP is not used, the probe is caught by the meniscus.
Credit: Kaoru Uesugi, Osaka University, Global Center for Medical Engineering and Informatics
A research paper by scientists at the Ibaraki University analyzed the rowing force of the water strider middle leg by direct measurement using a bio-appropriating probe and by indirect measurement using image analysis.
The new research paper, published on Nov. 17 in the journal Cyborg and Bionic Systems, reported the rowing force of water striders obtained by direct and indirect measurements, and analyzed the maximum force arrival time and the middle leg angular velocity of the direct and indirect force measurements.
“Rowing force of the middle leg of a water strider is one of the important factors affecting water repellency and applications in biomimetics, biomechanics and biology. However, many previous studies have been based on estimated leg rowing force and lack some credibility. Therefore, we tried to measure leg rowing force directly by a force transducer.” explained study author Dr. Keisuke Morishima, professor of Osaka University. In the direct measurement, water striders were set onto a sensor system and the rowing force of a middle leg of the set water striders was directly measured using a BAP, a kind of hook. In the indirect measurement, water striders were not fixed and the rowing force of locomoting water striders was evaluated by image analysis using a high-speed camera. “As a result, we determined the rowing force by the direct measurement to be 955 µN, while the rowing force by the indirect measurement was 488 µN.” said the author.
The microstructure of the water strider’s legs has been studied in developing semi-aquatic devices and robot. If more details about the rowing force are known, understanding will be deepened. “By determining and comparing the rowing forces which were measured by the direct and the indirect force measurements, we could discuss various properties of the water striders such as their water repellency, and we could also discuss applications to biomechanics and biology.” said Dr. Kaoru Uesugi.
The study authors proposed that measure leg rowing force directly by a force transducer. Additionally, in order to decrease the effect of a meniscus, a BAP was developed. By using the measurement method and system and the BAP, the rowing force by the direct measurement to be 955 µN, while the rowing force by the indirect measurement (image analysis) was 488 µN.
“There are a few studies which have dealt with direct and indirect force measurements. By comparing different types of force measurements, we successfully clarified the differences of these forces measured directly and indirectly.” said Dr. Kaoru Uesugi. Totally, the study can contribute to the fields of surface physics, biomechanics and biology, and inspiring innovation around it.
Authors of the paper include Kaoru Uesugi, Hiroyuki Mayama, Keisuke Morishima
This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI [grant number 22K03805].
The paper, “Analysis of Rowing Force of the Water Strider Middle Leg by Direct Measurement Using a Bio-Appropriating Probe and by Indirect Measurement Using Image Analysis” was published in the journal Cyborg and Bionic Systems on Nov 17, 2023, at DOI: 10.34133/cbsystems.0061.