Pasomphone Hemthavy

Adhesion between side surface of an elastic beam and flat surface of a rigid body

A theory of adhesion between an elastic beam and a rigid body is proposed using linear beam theory. Normalized force between the elastic beam and the rigid body considering adhesion of the side surface of the elastic beam is investigated theoretically. Adhesion of an elastic beam is important to analyze gecko adhesion, and peeling mechanism of an adhered film. This adhesion is also important in design of grip-and-release devices. The force between an elastic beam and a rigid body is investigated by considering shear force and total energy, and is obtained as a function of the displacement of the elastic beam. The proposed theory is different from Kendall’s thin-film peeling theory in terms of the elastic energy. The proposed theory considers bending elastic energy, whereas Kendall’s theory considers extension elastic energy. Two different contacts, line contact and area contact, are taken into account to discuss the loading and unloading processes in terms of the relation between the force and the displacement. Non-dimensional parameter, which relates to the work of adhesion and the specifications of the elastic beam, is introduced to explain the normalized maximum tensile force.

Pulse voltage determination for electrostatic micro manipulation considering surface conductivity and adhesion of glass particle

A model with surface conductivity and adhesional force is proposed to investigate the mechanism for electrostatic micro manipulation of a dielectric object using a single probe. The manipulation system consists of three elements: a conductive probe as a manipulator, a conductive plate as a substrate, and a dielectric particle as the target object for manipulation. The particle can be successfully picked up/placed if a rectangular pulse voltage is applied between the probe and the plate. The reliability of the picking up/placing operation is improved by applying a pulse voltage that is determined by a theoretical model considering surface conductivity and adhesion. To verify the theoretical prediction, manipulation experiment is conducted using soda-lime glass particles with radii of 20 μm and 40 μm.

Optimization of control parameters of a boost converter for energy harvesting

In order to maximize the energy efficiency for energy harvesting, a simplified circuit model using a boost converter and a capacitor is proposed. The circuit model allows the analysis of the whole systems theoretical energy efficiency and determination of the optimum control parameters. The optimum duty ratio is determined analytically and the optimum switching period numerically. This is important information for designing a switching controller that achieves both low power consumption and accurate maximum power point tracking. Moreover, the proposed theoretical energy efficiency is helpful for component selection when designing boost converters.

Mechanisms for Grip-and-Release Process of Adhesion Contact Using Material with Variable Elastic Modulus

Adhesion mechanisms with and without a defect for gripping and releasing objects are proposed, considering the adhesion between a semi-infinite elastic body and a rigid object with a sinusoidal surface roughness. These mechanisms are investigated theoretically. The total energy consists of the elastic term, the interfacial adhesion term, and the mechanical potential energy term due to the external pressure. The grip-and-release process is discussed in terms of the changes in the total energy and the contact width. The gripping stress can be expressed as a function of the elastic modulus. Using polymers with variable elasticity, the grip-and-release process is demonstrated experimentally and discussed in terms of the theory.

The effect of surface conductivity and adhesivity on the electrostatic manipulation condition for dielectric microparticles using a single probe

By clarifying the effect of surface conductivity and adhesivity on the electrostatic manipulation condition, a dielectric particle made of any material can be manipulated with surface conductivity. The manipulation system consists of three elements: a conductive probe as a manipulator, a conductive plate as a substrate, and a dielectric particle as the target object for manipulation. The particle can be successfully picked up/placed if a rectangular pulse voltage is applied between the probe and the plate. Four kinds of particle materials are used in the experiment: silica, soda-lime glass, polymethyl methacrylate coated by conductive polymer, and polystyrene coated by surfactant. The radius of each particle is 15 μm. A first-order resistor-capacitor (RC) circuit model is adopted to describe the effect of surface conductivity and adhesivity on the manipulation condition. The manipulation system is modeled as a series circuit consisting of a resistor and a capacitor by considering the surface conductivity. A detachment voltage is defined as the capacitance voltage to detach the particle adhered to the plate or probe. Parameters of the RC model, surface resistance, surface capacitance and detachment voltage are identified by a simulation and measurements. To verify the RC model, the particles behavior is observed by a high-speed camera, and the electrical current is measured by an electrometer. A manipulation experiment is demonstrated to show the effectiveness of the model. The particle reaction is observed for each duration and magnitude of the pulse voltage for the manipulation. The optimum pulse voltage for successful manipulation is determined by the parameters of the RC model as the standard. This knowledge is expected to expand the possibility of micro-fabrication technology.

Analysis of adhesive elastic contact between a silica glass lens and silicone rubber using the JKR theory

Contact between a silica glass lens and silicone rubber is experimentally investigated by simultaneously measuring displacement, force and contact radius. The relationship between these three parameters is derived using elastic theory. The discrepancy between the theoretical relationship and the experimental results is observed to increase as the deformation of the silicone rubber increases. Under smaller deformation conditions, the elastic theory shows good agreement with the experimental results, although infinite stress on the edge of the contact area is predicted in the theory, and time dependence and adhesion hysteresis are observed in all experiments. It is suggested that time dependence and adhesion hysteresis in contact are not induced by the deformation of the bulk of the silicone rubber, but are induced by surface effects. The result suggests that the applicability limit of the elastic theory must be carefully considered in the JKR analysis of point contact for polymers.

Criterion of detachment for grip-and-release devices with slanted multi-beam structure using Ti-Ni wire

A multi-beam structure using Ti-Ni wire to grip rough surfaces and control detachment was manufactured. The grip-and-release mechanism of the structure was investigated. The experimental results were analyzed with a model assuming beam theory and using a fracture criterion at the adhered interface. The fracture criterion of the adhesion interface is suggested to depend on the shear stress.

Evaluation of energy dissipation involving adhesion hysteresis in spherical contact between a glass lens and a PDMS block

Adhesion hysteresis was investigated with the energy dissipation in the contact experiments between a spherical glass lens and a polydimethylsiloxane (PDMS) block. The experiments were conducted under step-by-step loading–unloading for the spontaneous energy dissipation. The force, contact radius, and displacement were measured simultaneously and the elasticity of the PDMS was confirmed. The work of adhesion was estimated in the loading process of the strain energy release rate. The total energy dissipation has been observed to be linearly proportional to the contact radius in the unloading process. The approximately constant gradient of the energy dissipation for each unloading process has been found. The result would provide how the dissipation is induced during the unloading as some interfacial phenomena. The fact has been discussed with some interfacial phenomena, e.g., the adsorbates on the surface, for the mechanism of adhesion hysteresis.

Compliant bipolar electrostatic gripper with micropillar electrodes array for manipulation at macroscale

A compliant electrostatic gripper with bipolar voltage polarity for a pick-and-place manipulation is presented. The compliance, realized by the introduction of an array of micropillars which act as the electrode, extends the application of electrostatic-based gripper to manipulating fragile, rough-surfaced dielectric objects at macro scale. A prototype consisting of two arrays is developed by a chemical etching process. The experimental force is then compared with the theoretical force obtained from a simulation, showing a discrepancy between them. The sources of the discrepancy are analyzed to provide design insight for force improvement. To assess the reliability, the prototype is used for a manipulation demonstration of flat-surfaced paper. The result shows a good repeatability, and the necessary pick-up condition is confirmed. Subsequently, as the proof of the concept, another pick-up for rough-surfaced objects represented by a tissue paper with different roughness condition is also demonstrated. The effect of the rough surfaces to the generated forces is qualitatively discussed.

Change in temperature distribution by constriction of electric current through contact area

Abstract The change in temperature distribution due to constriction of an electric current through a contact area is analytically and numerically investigated. The potential distribution, current density distribution and heat density distribution inside the body are analytically obtained. The heat density has the singular point at the periphery of the contact area. It is revealed that the temperature has a finite value at the periphery, whereas the temperature change rate with respect to time has an infinite value because of the singularity. The results show the change in the temperature distribution. The times to melting and melting area are determined from the change in the temperature distribution. The total heat generated until melting occurs is also obtained.