Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Water striders' jumping on water -- understood and imitated after careful observations

06.08.2015

Jumping is an antipredatory adaptation of many water strider species to avoid capture by predators that attack from under the water surface.

The Korean-Polish team of biologists, Piotr Jablonski, Sang-Im Lee and Jae Hak Son from the Laboratory of Behavioral Ecology and Evolution (Jablonski, Lee and Son) and the Institute of Advanced Machines and Design (Lee) at the Seoul National University have filmed jumping behavior of the largest water strider species in Korea, Aquarius paludum.


Figure 1. Comparison between the robot (A) and its inspiration - the real water strider (B) during jump. The insect and the robot are not at the same scale because the aim is to focus on similarities in the dimples on the water surface created by legs of the robot (A) and the insect (B).. Although the robots themselves do not faithfully imitate the look and morphology of the real water striders, the interactions between the robot legs and the-water surface correctly reproduce the principal mechanism used by jumping insects. Therefore, the robot performance is comparable to that of the real water striders. They are the first robots that are similar to the larger water strider species in terms of body mass and jump physics as well as jumping performance. The two photos are screenshots from the video clips from Koh et al. 2015. Jumping on water: surface tension-dominated jumping of water striders and robotic insects. Science 31 July 2015, vol 349 no.6247 pp. 517-521.

Credit: Koh et al. 2015. Jumping on water: surface tension-dominated jumping of water striders and robotic insects. Science 31 July 2015, vol 349 no.6247 pp. 517-521.

Slow-motion movies shot at 1000 fps, showed that the typical jump has two phases. Video of the water strider Aquarius paludum jumping on a solid substrate clearly shows these phases (see the uploaded media "Water strider A paludum jump on solid substrate.wmv").

In the initial phase midlegs mostly press vertically downwards against the water surface. As a result of these leg movements, the water surface is deflected creating a dimple in the initial phase. The dimple is created gradually because the leg speed downwards increases gradually rather than abruptly.

In the second phase the legs move rather horizontally, first mostly backwards and then mostly inward with a gradual switch between them. The dimple then moves across the water surface as the legs move backwards and then inward (see the uploaded media "Water strider A paludum jumps on water.wmv" ) during 20-30 milliseconds between the initial phase and the moment when the legs leave the water surface.

THEORETICAL UNDERSTANDING

Based on the insect morphology and the pattern of the leg movements, the team of theoretical engineers, Ho-Young Kim and Eun-Jin Yang from the Micro Fluid Mechanics Laboratory and the Institute of Advanced Machines and Design at the Seoul National University, created a mathematical model of surface tension forces that make the vertical jump possible (a type of model called "kinematic model"). They estimated a threshold value for the dimple depth below which the legs will break the water surface.

Then, they calculated the vertical body speed of a jumping insect resulting from the interactions between legs and water surface. At the heart of these calculations is the fact that each leg of an insect creates a dimple on the water surface (provided it does not break the surface), and that at each moment of time the water strider experiences the upward directed force (component of the surface tension force) from each dimple.

The final jumping speed is proportional to the sum of forces acting on all four legs (four dimples) at each moment of time for the duration of jump. This means that the adding of the forces occurs in space (four dimples) and time (along the duration of jump). The upward force at each dimple increases as the dimple depth (strictly speaking volume) increases.

But, breaking of the water surface by legs, which occurs after the threshold depth is reached, leads to a loss of the dimple and the upward force. Therefore, the model predicted that the speed-maximizing jumping behavior is to keep the dimple as deep as possible for as long as possible without breaking the surface of water. The theoretical analysis suggested that the water strider's leg movement pattern observed by biologists allows insects to achieve this optimal jumping performance without breaking the water surface (as explained in a video in reference 2).

BUILDING JUMPING ROBOTS

Inspired by the biological observations and the theoretical understanding, the team of engineers, Kyu-Jin Cho, Je-Sung Koh, Gwang-Pil Jang, and Sun-Pill Jung from the Biorobotics Laboratory and the Institute of Advanced Machines and Design at the Seoul National University, together with Robert J. Wood from the School of Engineering and Applied Sciences and Wyss Institute for Biologically Inspired Engineering at Harvard University, began to design miniature robots.

They created a computer model of jumping (a type of model called "dynamic model") helpful in designing a robot that correctly reproduces the physical principle used by water striders in jumping. The new robots correctly imitate the core characteristic of the insect leg movements: initial gradual increase of downward force against the water surface, which creates the water dimple without splashing and without breaking of the water surface, followed by inward movements of the legs on the surface, which causes a shift of the unbroken dimple across the water surface (see movies of robots in reference 1, 2 and 3).

Although the robots themselves do not faithfully imitate the look and morphology of the real water striders, the interactions between the robots' legs and the-water surface correctly reproduce the principal mechanism used by jumping insects. Therefore, the robots' performance is comparable to that of the real water striders. They are the first robots that are similar to the larger water strider species in terms of body mass and jump's physics as well as jumping performance.

The earlier "water strider robots" that jumped on water did not relay on surface tension, created splashes breaking the water surface, and were much larger than the real water striders (see example in reference 4). None of them was based on as careful observations and understanding of nature as are the robots created by Kyu-Jin Cho, Je-Sung Koh, Gwang-Pil Jang, Sun-Pill Jung and Robert Wood.

These robots open exciting new possibilities to test hypotheses about evolution as an optimizing process that creates biological adaptations to jump. For example, in the future one can probably be able to build mini robots that are very similar to the existing water strider species (for example in terms of leg length) and compare them to the robots that are unlike the existing water strider species. If evolution creates morphologies for the best performance then the robots most similar to the real water striders will show the best jumping performance.

###

REFERENCES:

Reference 1: Koh JS, Yang E, Jung GP, Jung SP, Son JH, Lee SI, Jablonski PG, Wood RJ, Kim HY, Cho KJ. 2015. Jumping on water: surface tension-dominated jumping of water striders and robotic insects. Science 31 July 2015, vol 349 no.6247 pp. 517-521. Link: http://www.sciencemag.org/content/349/6247/517.short

Reference 2: Arstechnica news: Cathleen O'Grady (UK), Jul 31, 2015. "The first machine that can jump on water. Engineers use biomimentics to trun water surface tension into a Launchpad" Link: http://arstechnica.com/science/2015/07/the-first-machine-that-can-jump-on-water/

Reference 3: You tube video: "Scientists create insect robots that walk on water". by CCTV News, published on Jul 30, 2015. Link: https://www.youtube.com/watch?v=puSdwpv-X0k

Reference 4: Levi Sharpe, posted July 31, 2015. "Insect-like robot can jump on water". By Popular Science. http://www.popsci.com/insect-robot-can-jump-water

Media Contact

Sangim Lee
sang_im@hotmail.com
020-103-521-1959

http://www.behecolpiotrsangim.org/index.php 

Sangim Lee | EurekAlert!

More articles from Life Sciences:

nachricht Newly designed molecule binds nitrogen
23.02.2018 | Julius-Maximilians-Universität Würzburg

nachricht Atomic Design by Water
23.02.2018 | Max-Planck-Institut für Eisenforschung GmbH

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Attoseconds break into atomic interior

A newly developed laser technology has enabled physicists in the Laboratory for Attosecond Physics (jointly run by LMU Munich and the Max Planck Institute of Quantum Optics) to generate attosecond bursts of high-energy photons of unprecedented intensity. This has made it possible to observe the interaction of multiple photons in a single such pulse with electrons in the inner orbital shell of an atom.

In order to observe the ultrafast electron motion in the inner shells of atoms with short light pulses, the pulses must not only be ultrashort, but very...

Im Focus: Good vibrations feel the force

A group of researchers led by Andrea Cavalleri at the Max Planck Institute for Structure and Dynamics of Matter (MPSD) in Hamburg has demonstrated a new method enabling precise measurements of the interatomic forces that hold crystalline solids together. The paper Probing the Interatomic Potential of Solids by Strong-Field Nonlinear Phononics, published online in Nature, explains how a terahertz-frequency laser pulse can drive very large deformations of the crystal.

By measuring the highly unusual atomic trajectories under extreme electromagnetic transients, the MPSD group could reconstruct how rigid the atomic bonds are...

Im Focus: Developing reliable quantum computers

International research team makes important step on the path to solving certification problems

Quantum computers may one day solve algorithmic problems which even the biggest supercomputers today can’t manage. But how do you test a quantum computer to...

Im Focus: In best circles: First integrated circuit from self-assembled polymer

For the first time, a team of researchers at the Max-Planck Institute (MPI) for Polymer Research in Mainz, Germany, has succeeded in making an integrated circuit (IC) from just a monolayer of a semiconducting polymer via a bottom-up, self-assembly approach.

In the self-assembly process, the semiconducting polymer arranges itself into an ordered monolayer in a transistor. The transistors are binary switches used...

Im Focus: Demonstration of a single molecule piezoelectric effect

Breakthrough provides a new concept of the design of molecular motors, sensors and electricity generators at nanoscale

Researchers from the Institute of Organic Chemistry and Biochemistry of the CAS (IOCB Prague), Institute of Physics of the CAS (IP CAS) and Palacký University...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

2nd International Conference on High Temperature Shape Memory Alloys (HTSMAs)

15.02.2018 | Event News

Aachen DC Grid Summit 2018

13.02.2018 | Event News

How Global Climate Policy Can Learn from the Energy Transition

12.02.2018 | Event News

 
Latest News

Basque researchers turn light upside down

23.02.2018 | Physics and Astronomy

Finnish research group discovers a new immune system regulator

23.02.2018 | Health and Medicine

Attoseconds break into atomic interior

23.02.2018 | Physics and Astronomy

VideoLinks
Science & Research
Overview of more VideoLinks >>>