Pasomphone Hemthavy’s research while affiliated with Tokyo Institute of Technology and other places

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Publications (29)


Development of bipolar electrostatic chucks with a compliant beam-array assembly from composite-laminated plates using abrasive water jet
  • Article

August 2022

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25 Reads

MRS Advances

Tomohiro Ryo

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Pasomphone Hemthavy

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This paper describes the development of bipolar electrostatic chucks with a compliant beam-array structure using abrasive water jet technology. The chucks are cut out from 3D-printed composite-laminated plates and the attractive forces that they generate are measured. Their performance is compared with electrostatic chucks (ESCs) made using a 3D-printing method developed by previous research. The ESCs fabricated using the proposed method have better beam tips with straight corners and flat contact surfaces. Moreover, when comparing the percentage of the attractive force (per unit area) of a stacked device to a single module, the water jet ESCs perform better (77.2%) than the 3D-printed ESCs (57.8%). The higher performance is mainly because the proposed method has excellent fabrication repeatability, which allows the beam tips of a stacked device to have an aligned height. This fabrication method is expected to contribute to the mass production of ESCs.Graphical abstract


Development of Bipolar Electrostatic Chuck with a Beam-Array Assembly Fabricated by Lithography

July 2022

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22 Reads

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1 Citation

International Journal of Automation Technology

This technical paper demonstrates the influence of the probe-tip surface smoothness of a bipolar electrostatic chuck (ESC) on electrostatic force. ESC, which has a silicon-based beam-array microstructure, aims to pick and place a dielectric object with a curved surface owing to the compliance of its elastically deformable beams. The ESC was fabricated using a lithography technique, specifically deep reactive ion etching (DRIE), to smooth the surface of the beam tip. The surface roughness of the beam tips was observed using a field-emission scanning electron microscope (FE-SEM), and the adhesional force was experimentally evaluated. The results show that by the smoothing process, the adhesional force per unit area is significantly increased compared to the previous study reported by Choi (one of the authors). This suggests that the proposed bipolar ESC device has great potential for use in various industries.


(a) Concept of handling, (b) module design and attractive force generation, (c) cantilever model of a beam.
Schematic illustration of the two types of ESCs.
Fabricated stacked high-compliance ESC device.
(a) Schematic illustration of the experimental system, (b) experimental procedure.
Schematics of the attractive area.

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Development of a bipolar electrostatic chuck with a compliant beam-array assembly having four 3D-printed layers for large film handling
  • Article
  • Full-text available

January 2022

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166 Reads

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4 Citations

This study proposes and verifies bipolar electrostatic grippers stacking 3D-printed-layered modules consisting of arrays of elastically deformable bipolar beams. The influence of the mechanical compliance of grippers on the attractive force that it generates is clarified by comparing two types of modules having either high or low mechanical compliances. Experiments measured the attractive force of the gripper and demonstrated the pick-and-place performance of a thin film. The results show that mechanical compliance plays an important role in mitigating the attractive force decrease in stacking modules. The grippers’ ability for thin film handling is demonstrated by observing pick-and-place behaviours of the proposed bipolar electrostatic grippers.

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Proposal and applicability of a method to evaluate surface tension of liquid using large volume sessile drop in gravity

January 2021

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33 Reads

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1 Citation

Welding International

Based on a theory of sessile drop in gravity, a method to evaluate surface tension is proposed, and its applicability is discussed. All of parameters are theoretically normalized. Although it is impossible to obtain analytic solution of the surface profile of the sessile drop, it is possible in an extreme condition of large volume. A universal parameter which determines the volume of liquid is derived in a normalized form. The large volume condition is theoretically defined using the parameter. Under the large volume approximation, an equation is derived which gives the surface tension from a height and an angle of the drop surface. In order to discuss applicability of the approximation, numerical calculation is carried out. It is found that the surface tension can be obtained with a tolerance less than 16%, if we measure the height of the sessile drop and the contact angle, under the large volume approximation. This method proposed in the present study is beneficial for the estimation of wettability of liquid using sessile drop.


Adhesional rolling behavior of micro-cylinder: Experimental observation of adhesional contacts and measurement of critical rolling resistance

December 2020

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86 Reads

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3 Citations

There has been much research offering theoretical explanations of rolling behavior considering the effect of adhesion, which is essential when the object is small. However, there has been a shortage of experimental verifications because objects are too small to manipulate and observe directly. This study measured the moment and observed the contact area before, during, and after rolling with an experimental setup on a relatively large scale. The experiment setup consisted of two glass cylinders which were placed in between two PDMS blocks. This paper reports three main findings: the results suggest that viscosity influences the transition of states of the contact. The critical rolling resistance is dependent on the radius of the cylinders and the applied weight to the cylinders. The results support the theoretical expectation of the value of a critical rolling resistance, which is the product of the radius of the cylinders and the work of adhesion. This study offers experimental foundations to develop theories of rolling of micro-cylinders.


Adhesional Contact between Rigid Sphere and Elastic Plane Covered with Thin Liquid Film Considering Contact-Angle Hysteresis

January 2020

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58 Reads

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1 Citation

Tribology Online

This paper proposes a contact model between a rigid sphere and an elastic plane covered with a thin liquid film. The elastic contact is determined by Johnson–Kendall–Roberts theory, which deals with the energy equilibrium of elastic and interfacial energies. In elastic contact under presence of thin liquid film, the energy needed to separate the two bodies is defined as the summation of the interfacial energy among the sphere, liquid, and plane. Capillary force affects the two bodies because a liquid bridge is formed between them. Shape of the liquid bridge, assumed by the Clark’s toroidal approximation, determines the capillary force. The hysteresis of the liquid contact angles and that of the liquid volume between loading and unloading processes are considered. In loading process, the liquid film is squeezed out from the contact area and accumulates at the contact edge with increasing the liquid contact angles. In unloading process, the accumulated liquid is dragged to the contact edge, and the contact angles decrease. An irreversible force curve is obtained from these two hystereses, and the effect of liquid bridge is discussed based on the calculated results. In addition, the adhesion-hysteresis mechanisms caused by the capillary force are discussed.


Compliant bipolar electrostatic gripper using 3D-printed-layered elastic probes

January 2020

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193 Reads

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10 Citations

A 3D-printed-layered structure for forming the compliant bipolar electrostatic gripper is proposed. A prototype gripper module, which consists of an array of elastically deformable bipolar micro-probes, is fabricated using a conventional 3D printer. Experiments are conducted to examine the attractive force and the pick-and-place performance of the prototype. Experimental results show that the prototype module can generate the maximum attractive pressure of 87.1 Pa, which can pick and hold a piece of xerographic paper of 31.2 mg successfully. The effects of residual charges and the probe-tips flattening process on the attractive force are also discussed.


Analytical solution of elastic deformations inside and outside circular contact area between tilted rigid punch and elastic half space

December 2019

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109 Reads

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3 Citations

Acta Mechanica

This paper proposes an analytical model for the Boussinesq problem between a tilted rigid punch and an elastic half space to enable the analysis of elastic deformations inside and outside a contact area. Inside the contact area, two types of pressure distributions are applied: one generates a flat elastic deformation, and the other produces a tilted elastic deformation. The projection of this elastic deformation varies depending on the observed horizontal direction because the elastic deformation is non-axisymmetric. To calculate integrals for the non-axisymmetric elastic deformation, we use the polar coordinate system with two angular coordinates, which can enable the calculation of an integral at any arbitrary point. The proposed model can obtain the relationship between the pressure distribution and the elastic deformations inside and outside a contact area from any arbitrary direction. In addition, the normal load and torque applied inside the contact area are obtained, and these parameters are normalized using the contact radius and the elastic modulus. At the zero-pressure point around the contact edge, the elastic deformation is smooth.


Two designs of electrodes structure in a single fiber with their corresponding cross-sectional images. The targeted diameter of the fiber is 400 μm. Design 1 depicts a structure consisting of parallel electrodes whereas Design 2 depicts electrodes in a coaxial structure. Each design allows for a positive and negative voltages to be applied which eventually result in a gripping force. The structure of a beam-array at an angle favors the handling of an object with rough surfaces.
(a) Cross-sectional images of the fabricated fibers, taken by SEM for the fiber with parallel electrodes (Design 1), and (b) Fiber with coaxial electrodes (Design 2); (c) Experimental setup for force measurement using an analytical balance; (d) geometrical settings for each fiber design used in the numerical simulations.
Graph of force values with varied distance between fibers’ tip and dielectric object.
Schematics of array and polarity pattern of fibers for expansion. (a) Fibers are arranged in squared arrays with interval of L. (b) Two kinds of polarity patterns for each of parallel and coaxial design; Pattern 2 is designed such that more electric field boundaries are present.
(a) Simulation results showing the normalized electrostatic force per fiber when the number of fibers and the arrangement intervals are varied, (b) simulation results comparing the normalized electrostatic force density for different proposed combination of designs and patterns of the fibers.
Force evaluation of electrostatic gripper with arrayed fibers consisting of parallel and coaxial electrodes

August 2019

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101 Reads

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4 Citations

Electrostatic gripper is a technology that has seen many advancements in the last few decades. Its popularity among researchers is due mainly to many advantages it offers, e.g. its ability of a simple force control by adjusting the applied voltage to the electrodes. The electrostatic gripper with voltages of positive and negative polarities is particularly deemed promising as it can handle various materials, especially dielectrics, by the principle of polarization due to the electric fields. In this work, an electrostatic gripper with a beam-array structure made of conductive polymeric fibers is considered. The structure of coaxial electrodes has been understood to sport a superior performance; however no comparative analysis has been reported so far. Thus, this work offers an empirical comparison between fibers consisting of coaxial and parallel electrodes by experiments which are validated by numerical simulations. Furthermore, utilizing numerical simulations, design guidelines, especially concerning the voltage polarity patterns are established. The results are expected to shed an insight toward the development of a full-fledged electrostatic gripper for industrial use.


Effect of smoothness of contact tips and length of micro-hairs on electrostatic force of the silicon bipolar electrostatic chuck having hairy microstructure微細毛構造を有するシリコン双極型静電チャックの接触面の平滑さと微細毛長が静電力に与える影響

January 2018

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6 Reads

The Proceedings of the Symposium on Micro-Nano Science and Technology

In this study, we fabricated a bipolar electrostatic chuck having hairy silicon-based microstructure with smooth contact surface by lithography technology. Using DRIE, we succeeded in creating electrostatic chuck structure with high surface accuracy. We deserved the surface of tips observation with FE-SEM , and evaluated the performance by force curve measurement. The state of detachment could be detected by monitoring the transition of force-displacement in force curve measurement .As a result, compared to previous research, the adhesion per unit area greatly improved. Additionally, we obtained guidelines for further improvement in performance.


Citations (14)


... Over the past decade, various alternative approaches to vdW forces have been proposed to address the significant challenges in developing gecko-inspired adhesives for practical applications [38][39][40][41][42][43][44][45]. Among these alternatives, electrostatic forces, due to their long-range nature, have been identified as a primary source of gripping and adhesion [40][41][42][43][44]. ...

Reference:

Fabrication and electroadhesion properties of parylene-coated carbon fiber arrays
Development of a bipolar electrostatic chuck with a compliant beam-array assembly having four 3D-printed layers for large film handling

... Despite being able to explain certain phenomena, Coulomb's formula remains a subject of controversy [4]. Currently, researchers have put forward various mechanisms to explain rolling friction including micro-sliding friction on contact surfaces [5], nonlinear deformation of contact solids [6,7], viscous hysteresis [8][9][10][11][12][13], and surface adhesion [14]. The viscous hysteresis mechanism is widely employed to elucidate energy dissipation in rolling contact. ...

Adhesional rolling behavior of micro-cylinder: Experimental observation of adhesional contacts and measurement of critical rolling resistance

... The selectable range of detecting force area is limited according to the shortened load distance. Thus, the data that include adhesion energy are used to convert PD sensitivity, and that is the cause of increased PD sensitivity [21]. ...

Adhesional Contact between Rigid Sphere and Elastic Plane Covered with Thin Liquid Film Considering Contact-Angle Hysteresis

Tribology Online

... Theoretically, a lower effective elastic modulus allows for greater deformation under load and improved compliance, meaning that fibers can better conform to rough surfaces during the adhesion process. This low elastic modulus is considered crucial for adhesion, particularly with rough surfaces [47,48]. ...

Compliant bipolar electrostatic gripper using 3D-printed-layered elastic probes

... However, these models are also based on the phenomenological approach developed in [17,18]. At the same time, the continuum mechanics papers devoted to contact interaction are mostly focused on study of the contact and internal stress distribution and the energy losses for various loading conditions and type of motion [19][20][21][22][23], thermo-effects [24] and wear [25]. This lack between the fields indicates that it is necessary to use the contact mechanics models for analysis of the system dynamics. ...

Analytical solution of elastic deformations inside and outside circular contact area between tilted rigid punch and elastic half space

Acta Mechanica

... Since batteries fail to keep pace with the demands of such devices, especially in terms of energy density, life span, and maintenance cost [1,2], the proliferation of low-power devices raises the problem of effective power supply. A promising approach to solving this problem is to convert kinetic energy into electric power by exploiting various mechanisms for operation, including thermoelectric [3,4], electrostatic [5,6], electromagnetic [7,8], piezoelectric [9,10], and triboelectric [11,12]. Among these operational mechanisms, piezoelectric energy harvester (PEH) has attracted wide attention owing to their high energy density, strong electromechanical coupling, simple structures, and good compatibility with microelectromechanical systems [13][14][15]. ...

Force evaluation of electrostatic gripper with arrayed fibers consisting of parallel and coaxial electrodes

... Nonetheless, results in Fig. 2(a,b) clearly show that viscoelastic dissipation induces large adhesive hysteresis in A-R cycles at intermediate values of̃. These findings are in agreement with experimental results (Giri et al., 2001;Baek et al., 2017;Li et al., 2019;Ahn and Shull, 1996) and show that, during retraction, the system is able to withstand significantly larger tensile loads compared to the elastic case, as also shown in Violano and Afferrante (2019), Li et al. (2019), Baek et al. (2017), Lorenz et al. (2013), Das and Chasiotis (2021). A closer look at Fig. 2(a) reveals that the maximum tensile stress (pull-off) can either occur at larger retraction distances compared to the elastic JKR and, for relatively large A-R speeds, even at positive penetration > 0, in agreement with experimental results (Linghu et al., 2023;Giri et al., 2001). ...

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

Applied Adhesion Science

... Therefore, the need for thin-film handling methods for flexible displays may be fulfilled with an ESC that can passively deform during placement on curved surfaces. Bipolar ESCs with compliant beams were developed to satisfy the requirements above [19][20][21][22]. Previous studies have fabricated ESCs with a beam-array assembly using several methods, such as lithography and additive manufacturing [21,22]. ...

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

... Some papers suggest that the adhesion force is determined not only by the JKR or DMT theory but also by the theory of the liquid-bridge effect [24,[27][28][29][30][31][32]. A liquid bridge is categorized into two patterns: one is the capillary condensation, and the other is the liquid-film distribution on the surface. ...

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

... Nevertheless, this approach is susceptible to temperature variations and water-related damage and necessitates an additional temperature control module. Saito et al. [17], [18] implemented the electrostatic-force-based picking of conductive and dielectric microbeads, achieving a reliable dielectric microparticle pickup operation. However, this operation presents difficulties in assembling nonconductive microdevices and potential risks to microelectronic devices due to the electric field between the substrate and the probe. ...

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