Development Of Synchronous Measurement System For Contact Force,Real Contact Area And Tribo-charge Of Moving Gecko

Gecko's ability of strong adhesion and outstanding regulation on a variety of surfaces has being a research focus in the field of biology.Various hypothesizes are proposed as the gecko's adhesion mechanism,the major view is that VDW interaction plays the dominant role in gecko's dry adhesion.However,increasing evidences show that electrostatic interaction caused by contact can significantly affect the interfacial force between gecko toes and the substrate.In order to carry out quantitative research and reach a deep understanding of electrostatic interaction's contribution in gecko adhesion,a synchronous measurement system of contact force,real contact area and tribo-charge has been developed.Mature approaches are available for individual measurement of contact force,real contact area and tribo-charge,multiple constraints will be introduced when achieving the synchronous measurement: the sensor element is required to have light quality and good dynamic performance for force measurement,high light transmittance for real contact area measurement and excellent electric conductivity for tribocharge measurement.New challenges are brought in: transmittance and conductivity cannot be achieved simultaneously and multiple measurement functions leads to the increase of overall quality.In this paper,a combined sensor composed of force sensors,a PMMA slice coated with indium tin-oxide(ITO)film and light sources has been developed to resolve the conflicts between measurement methods and realize the synchronous measurement.two 3D force sensors are combined with PMMA slice to measure the contact force;light spot is formed in the real contact area to measure the real contact area based on the principle of suppressed total reflection of light;the transparent electrode generates the induced charge to measure the contact electricity.On this basis,the measurement system is constructed using a combined sensor array,a self-made signal conditioning and data acquisition system is applied to capture force signals and electrical signals,the contact spot is recorded by a high-speed camera.Data processing is carried out by host computer procedure based on Lab VIEW and image processing program based on MATLAB.Verification experiment of gecko crawling on the vertical surface is then carried out,and the strict experimental operation process and data screening principles are established.The preliminary experimental data show that the system meets the synchronous measurement requirements of the above parameters.Synchronous measurement system designed and developed in this paper provides equipment foundation for studying the contribution of electrostatic interaction in gecko adhesion,which helps to reach a deeper understanding in gecko's adhesion mechanism,and also brings relevant enlightenment to the preparation of dry adhesive materials and the development of gecko robots.