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

This message can help answer key questions in the biology, robotics, and fluid dynamics field in understanding the single-cell manipulation tactile, stancing, and a job called lessons process"The men at Rare Tech offer this technique, is that the macrodynamic force can be married with high sensitivity, which can expedite the whole interaction process. The oldest measure can provide insight into the adhesion force between water striders and the water surface. It can also be supply to other systems such as DNA injection and gene therapy.

integration or system assembly and software usage is critical, as it's difficult to display and process the voltage signal, or the PVDF film sensor in the computer. Assemble the dynamic force measurement system according to this schematic illustration shown in the text protocol. Fix one side of the PVDF film sensor with the electrodes to the high precise displacement stage, which is placed on the horizontal frame, leaving the other side hanging.

This installation method of the PVDF film sensor helps improve the resolution of the environment for the dynamic macro force. Connect the PVDF film sensor to the charge amplifier, the charge amplifier to the data acquisition device, and the data acquisition device to the computer. Fix the camera to the frame.

Adjust the camera's position and focus to film water and legs clearly. In order to roughly adjust the distance between the water strider legs and water, fix a high-precise displacement stage to the frame above the PVDF film sensor, whose separation from the PVDF film sensor is about 10 centimeters. To lift the water strider leg away from the water surface at a precise speed, fix the servomotor below the high-precise displacement stage.

Prior to starting the calibration of the Dynamic Force Measurement System, download the lab view software and the hardware driver in the official website of National Instruments. Use the electrostatic force system to generate a micro-constant force acted on the free end of the PVDF film sensor, whose magnitude should be less than 0.5 micronewtons. Control the electrostatic force of the system by a voltage applied to the inner and outer electrodes of the parallel cylindrical capacitor.

The force should act in a direction particular to the surface of the PVDF film, and the point O application is supposed to be as close as possible to the tip of the PVDF film sensor to increase sensitivity. Release the force in a short time to generate a step input. Read the voltage time signal in the computer using the LabView software, which helps read the output voltage signals of the PVDF film sensor.

Open the demo of the continuous analog voltage measurement. Select the physical channel of the data acquisition device connected with the charge amplifier in the module of channel settings. Set the sample rate to 100, 000, and the number of of samples to 100, 000 in the module of time settings.

Select the Log and Read'as the Logging Mode, and write the file path to store the voltage data in the module of Logging Settings. Also, select No trigger'in the module of Trigger Settings. Click the arrow-shaped button in the toolbar to sample the voltage signal.

Analyze the voltage curve in which the peak voltage corresponds to force acted on the sensor. Repeat these steps at different force input, in which a series of voltage force points are gained. Determine the relationship about the peak output, voltage and standard force in the calibration result.

To perform the measurement, first place a water drop on the free end of the PVDF film sensor using a mechanical micro-pipette. The location of the droplet should be close to the tip of the PVDF film sensor. Now, place a single leg to the servomotor below the high-precise displacement stage.

Move the high-precise displacement stage downward until the leg contacts with the water surface. Monitor the distance between the leg and water surface by the camera system mounted on the left side of the sensor. Then, lift the leg away from the water surface at a constant speed through the servomotor.

Calculate the force corresponding to each point of the voltage curve of the departing process as described in the text protocol. To measure adhesion force at different speeds, alter the lifting speed of the legs by the servomotor, and measure the adhesion force as before. Then plot the adhesion force versus lifting speed curve using the data gained from lifting the leg.

Shown here is the real-time adhesion force measured by the PVDF film sensor in the departing experiment of the legs at a certain speed. The results of the departing experiment show that the adhesion force decreases dramatically from 0.10 micronewtons to 0.03 micronewtons, with an increase in lifting speed from 0.0 meters per second to 0.3 meters per second. When attempting this procedure, it's important to remember to change the glide of water strider to avoid them being wetted by water, which helps improve accuracy of this experiment.

Generally, individuals new to this measure will struggle because PVDF film sensor may be influenced by the electromagnetic interference and the vibration in the environment. It's crucial that the adhesion force is measured at a different speed by lifting the leg from the water surface. As the study focuses on the remarkable characteristics of quicker maneuvering on the water.

After its development, this technique paved the way for the researchers in the field of biology to explore the adhesion force of the water strider departing from the water surface in the Dynamic Force Measurement System.