Development of a capillary force measurement system for wet adhesion

Master thesis (2021)

Authors

C.H. Jongerius Mechanical Engineering

Contributors

D. Dodou Medical Instruments & Bio-Inspired Technology - Mechanical, Maritime and Materials Engineering (supervisor 1)
Julian K.A. Langowski Wageningen University & Research (supervisor 1)
Preeti Sharma Wageningen University & Research (supervisor 2)
B. Bera ChemE/Transport Phenomena - AS (coach)
Faculty
Mechanical Engineering
Copyright: © 2021 Camiel Jongerius
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Published Date

10-11-2021

Language

English

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Faculty

Mechanical Engineering

Abstract

The study of adhesion mechanisms in animals such as the gecko has helped mankind with the understanding and development of novel adhesives. The adhesion mechanism of the tree frog is not fully understood, it is a wet adhesion mechanism which works differently than the dry adhesion mechanisms of animals, such as the gecko, studied previously. The wet adhesion mechanism of the tree frog may be based on the capillary force present in liquids. Researching the adhesion mechanisms of the tree frog could help develop new capillary based
adhesives. Although there are several capillary measurement methods and devices used to study the interactions between small volumes of liquids and surfaces, they would require the frog to be immobilized for accurate measurements, which constitutes as harm. This thesis begins the design and development of a system to measure the capillary force created by tree
frogs without harming them. The selected concept functions with the use of a pressure sensor connected to the capillary pressure source with capillary channels. This concept allows for a precision of 12Pa determined by the pressure sensor and a responsiveness of 30 ms determined by fluidic circuit while allowing the frog to roam free around the system input. The components were tested to verify their functionality. A controlled pressure source is used to verify the calibration of the sensor, the time constant and hydraulic capacitance; which are
the parameters that determine the accuracy and responsiveness of the system. The sensor was successfully calibrated to measure pressure linearly up to 10 kPa but the time constant and hydraulic capacitance were experimentally measured to be three orders of magnitude larger than the estimated parameters of the components. In order to solve the disparity between the experimental and theoretical values, different tubing and connections were suggested to reduce the hydraulic capacitance and a method verifying the presence of air bubbles was advised. A Sesille drop experiment was performed on the pressure sensor in order to support the principle of measurement, the results suggests the principle of measurement is valid but the issues surrounding the fluidic circuit needs to be resolved in order to complete the system.