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Measurement of Dynamic Force Acted on Water Strider Leg Jumping Upward by the PVDF Film Sensor

Published: August 3rd, 2018



1State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University

The protocol here is dedicated to investigating the free and quick maneuvering of water strider on water surface. The protocol includes observing the microstructure of legs and measuring the adhesion force when departing from water surface at different speeds.

This study aimed to make an explanation for the phenomenon in nature that water strider usually jumps or glides on the water surface easily but quickly, with its peak locomotion speed reaching 150 cm/s. First of all, we observed the microstructure and hierarchy of water strider legs using the scanning electron microscope. On the basis of the observed morphology of the legs, a theoretical model of the detachment from water surface was established, which explained water striders' capability to slide on water surface effortlessly in terms of energy reduction. Secondly, a dynamic force measurement system was devised using the PVDF film sensor with excellent sensitivity, which could detect the whole interaction process. Subsequently, a single leg in contact with water was pulled upward at different speeds, and the adhesion force was measured at the same time. The results of the departing experiment suggested a deep understanding of the fast jumping of water striders.

In nature, water striders possess remarkable ability to jump or glide easily and rapidly on the water surface with the help of the slender and nonwetting legs1,2,3,4,5, but seldom move slowly, which is unlike the terrestrial insects. The hierarchical structure of water strider stabilizes the superhydrophobic state, which renders dramatic reduction in contact area and adhesion force between water and the leg6,7,8

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1. Observation of the Surface Structure on Water Strider Leg

  1. Collect water striders from local freshwater ponds using fishing landing net.
  2. Cut off at least 5 pairs of middle legs as experimental samples using scissors. Touch the bottom of the legs carefully, to prevent the surface contamination and the disrupting of microstructure in the front of legs.
  3. Dry the legs out in the air naturally.
  4. Observe the surface microstructure of legs using a scanning electron microscope with micro.......

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The relation between lifting speed and adhesion force is shown in Table 1. When the lifting speed increases from 0.01 m/s to 0.3 m/s, the adhesion force between the water surface and leg decreases dramatically from 0.10 to 0.03 . The results of the departing experiment showed that the peak adhesion force would decrease dramatically as the lifting speed increase, which indicated that the water striders may feel comfortable if they move quickly on water surface.

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In this protocol, a dynamic force measurement system based on the PVDF film sensor was successfully devised, assembled, calibrated to measure the adhesion force away from the water surface. Among the whole steps, it was crucial that the adhesion force was measured at different speeds by lifting the leg from the water surface as this study focused on the remarkable characteristic of the quick maneuvering on the water. The results of departing experiment showed that the adhesion force decreased when the lifting speed incre.......

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The authors thank the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (No. 2011BAK15B06) for their support. Thank Shuya Zhuang who is a master student from our laboratory for helping us complete the video shoot.


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Name Company Catalog Number Comments
PVDF film sensor TE Connectivity DT1-028K/L The PVDF film sensor is used to sense the dynamic contact force .
Charge amplifier Wuxi Shiao Technology co.,Ltd YE5852B The charge amplifier is an electronic current integrator that produces a voltage output proportional to the integrated value of the input
Data acquisition device National Instruments USB-4431 The data acquisition device is used to read the voltage data.
Displacement stage ZOLIXINSTRUMENTS CO.LTD KSAV1010-ZF KSAV1010/2030-ZF is a wedge vertical stage with high-resolution, high-stability and high-load.
CCD camera Shenzhen Andonstar Tech Co., Ltd digital microscope A1 Frame rate: 30 frames/sec;Focal distance: 5mm - 30mm
Computer Lenovo G480
Servomotor EMAX US Inc. ES08MD It's not bad this servo with speed varying from 0.10 sec/60° / 4.8v to 0.08 sec/60°/6.0v.
Mechanical Pipettes Dragon Laboratory Instruments Limited YE5K693181 The pipettes cover volume range of 0.1 μl to 2.5 μl

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