Measurement and Characterization of Stiction Force in Microstructures With Tapered Features

2011 ◽  
Author(s):  
Christopher Pelzmann ◽  
Laxman Saggere
Keyword(s):  
Plane Surface ◽  
Van Der Waals ◽  
Theoretical Models ◽  
Adhesive Force ◽  
Van Der Waals Force ◽  
Curved Surface ◽  
Force Model ◽  
Curved Surfaces ◽  
Surface Geometry ◽  
Adhesive Forces

Modeling and measurement of stiction or adhesion due to van der Waals force between microstructures and micro-gripper tools are important for contact-based manipulation and assembly of microstructures. Microfabricated structures commonly feature rough tapered curved surfaces due to undercutting and surface alterations inherent in the microfabrication processes. While several theoretical models exist for calculating adhesive forces between microstructures featuring spherical, cylindrical and flat surfaces, a model for estimating adhesive forces between microstructures featuring tapered curved surfaces is lacking in the literature. This paper presents experimentally measured values of adhesion or pull-off force between a rough tapered curved microstructure from a rough plane surface using a custom micro-cantilever beam as a force sensing mechanism. The paper also introduces an approach to estimate adhesive force between a tapered curved surface and a flat surface by considering the tapered curved surface as a frustum of a cone bound between two cylinders and using the van der Waals force model for cylinders. It is shown that the experimentally measured adhesive force values lie within the upper and lower values of the theoretically estimated van der Waals force values for the two cylinders that define the tapered curved surface geometry.

Analysis of Pressure Distribution on Head Disk Air Bearing Slider Involved Van der Waals Force

2013 ◽  
Vol 419 ◽  
pp. 111-116
Author(s):  
Hong Rui Ao ◽  
Ming Dong ◽  
Xi Chao Wang ◽  
Hong Yuan Jiang
Keyword(s):  
Pressure Distribution ◽  
Van Der Waals ◽  
Disk Drive ◽  
Van Der Waals Force ◽  
Flying Height ◽  
Force Model ◽  
Air Bearing ◽  
Analysis Process ◽  
Before And After ◽  
Bearing Force

This paper focuses on the pressure distribution on the surface of slider in hard disk drive when its flying height is in nanoscale. The gas rarefaction effect and van der Waals force are involved in the analysis process. Here the air bearing force model is based on F-K model and we establish the equation of van der Waals force between the head and disk. Using the finite element method, the modified Reynolds equation and the van der Waals force were obtained. The air bearing force on slider before and after the van der Waals force involved were compared. The results illustrate that the effect of van der Waals force on the air bearing force is different according to the slider shapes and flying heights. As a result, van der Waals force plays an important role when the flying height of slider is below 10 nm.

Meniscus Adhesion at Ultra-Low Flying Slider-Disk Interfaces

2005 ◽  
Author(s):  
C. Mathew Mate ◽  
Robert N. Payne ◽  
Peter Baumgart ◽  
Kathy Kuboi
Keyword(s):  
Experimental Evidence ◽  
Van Der Waals ◽  
Adhesive Force ◽  
Air Bearing ◽  
Disk Drives ◽  
Bearing Surface ◽  
Slider Air Bearing ◽  
Adhesive Forces

As head-disk spacings in disk drives approach a few nanometers, adhesive forces between the slider and disk can drastically alter the slider flying dynamics. At these small separations, it is still unclear, however, what type of adhesive force dominates. Most previous studies have concentrated on van der Waals and electrostatic attractive forces [1], which are readily incorporated into air bearing simulations. In this talk, we provide experimental evidence that the dominant adhesive force originates from menisci forming around the low flying portions of the slider air-bearing-surface as the spacing transitions from near-contact to contact.

Modelling of Adhesive Forces in Nanotweezer

2011 ◽  
Vol 403-408 ◽  
pp. 1122-1129
Author(s):  
Amir Sanati Nezhad ◽  
Ion Stiharu ◽  
Muthu Packiricamy ◽  
Rama B. Bhat Mechanical
Keyword(s):  
Electrostatic Force ◽  
Van Der Waals ◽  
Adhesive Force ◽  
Object Size ◽  
Gap Size ◽  
Pick And Place ◽  
Contact Surfaces ◽  
Vdw Force ◽  
Nano Size ◽  
Adhesive Forces

In nano manipulation, carbon nanotubes (CNT) mounted on the AFM tip was used for pick and place of the nano size objects. In releasing step, the van der Waals adhesive force among the object and the contact surfaces of the gripper is not still well understood. In this paper, the adhesive electrostatic force, van der Waals (VDW) force between two cantilever tips and VDW force among cantilevers and the object are considered as dominant forces to pick and place the nano object. The equations governed on nanotweezer are solved using FEM code. The effect of object size, gap size and tips length on pull-in voltage are evaluated. The presented model could be used to design the tweezers for pick and place of size-defined nano object mounted on microgripper.

Effects of Contact Force Model and Size Distribution on Microsized Granular Packing

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
Xin Dou ◽  
Yijin Mao ◽  
Yuwen Zhang
Keyword(s):  
Particle Size ◽  
Contact Force ◽  
Van Der Waals ◽  
Van Der Waals Force ◽  
Particle Packing ◽  
Force Model ◽  
Size Distributions ◽  
Structure Variation ◽  
Packing Structure ◽  
Granular Packing

Granular packing of microsized particles with different size distributions and contact force models is studied using discrete element method (DEM). Three kinds of size distributions, monosized, uniform, and Gaussian, with mean diameter of 50, 60, and 70 μm are studied. Two aspects of microscale particle packing issues are addressed: one is the importance of van der Waals force when the particle size approaching to microscale, the other one is the structure variation caused by different contact force models. The results indicate that compared with contact force, the van der Waals force contributes very insignificantly to the final packing structure. The packing structures obtained using two different force models are similar to each other. The effects of particle size and its distribution on the packing structure are more significant than the force model.

Discussion on the Relation between the Adhesive Force of Drosophila Melanogaster and the Surface Roughness of the Substrate

2012 ◽  
Vol 159 ◽  
pp. 93-98
Author(s):  
Rui Guo Cui ◽  
Wei Dong Yu
Keyword(s):  
Surface Roughness ◽  
Drosophila Melanogaster ◽  
Van Der Waals ◽  
Adhesive Force ◽  
Van Der Waals Force ◽  
Basic Form ◽  
Adhesive Pads ◽  
R Value ◽  
Friction Plate ◽  
Gripping Force

Three forms of animals’ adhesion were analyzed: hairy adhesive pads, smooth adhesive pads and claw. Scanning electron microscope (SEM) was used to observe the surface of friction plate with different particle diameters. It’s found that the particle could be seen as conical shape. The self-designed lever-like testing equipment was also used to measure the adhesive force of drosophila melanogaster contacting 6 substrates with different roughness. It was shown that adhesive force decreased first and finally rose with the increase of surface roughness. When the roughness (R value) was about 68.5nm, it showed that the lowest adhesive force was 0.0085mN. Then model of the Van der Waals force was established. In this model, contact form between seta and the substrate was divided into five states, and the theoretical adhesive force at each state was calculated, which successfully simulated with the actual value. However, when surface roughness reached the situation that the gap between adjacent particles was greater than 2μm, the gripping function of the claw made the actual value greater than theoretical one. It was concluded that adhesive force was a compound function of the Van der Waals force generated by hairy adhesive force and the gripping force generated by claw. So it was also speculated that the fibrous fine pads of insects were the basic form adhesion on smooth surface of the substrate.

scholarly journals First-Principles Study on Graphene/Mg2Si Interface of Selective Laser Melting Graphene/Aluminum Matrix Composites

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 941
Author(s):  
Zhanyong Zhao ◽  
Shijie Chang ◽  
Jie Wang ◽  
Peikang Bai ◽  
Wenbo Du ◽  
...  
Keyword(s):  
Interfacial Energy ◽  
First Principles ◽  
Lattice Mismatch ◽  
Van Der Waals ◽  
Aluminum Matrix ◽  
Van Der Waals Force ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Charge Density Difference ◽  
Interface Charge

The bonding strength of a Gr/Mg2Si interface was calculated by first principles. Graphene can form a stable, completely coherent interface with Mg2Si. When the (0001) Gr/(001) Mg2Si crystal plane is combined, the mismatch degree is 5.394%, which conforms to the two-dimensional lattice mismatch theory. At the interface between Gr/Mg2Si, chemical bonds were not formed, there was only a strong van der Waals force; the interfaces composed of three low index surfaces (001), (011) and (111) of Mg2Si and Gr (0001) have smaller interfacial adhesion work and larger interfacial energy, the interfacial energy of Gr/Mg2Si is much larger than that of α-Al/Al melt and Gr/Al interfacial (0.15 J/m2, 0.16 J/m2), and the interface distance of a stable interface is larger than the bond length of a chemical bond. The interface charge density difference diagram and density of states curve show that there is only strong van der Waals force in a Gr/Mg2Si interface. Therefore, when the Gr/AlSi10Mg composite is stressed and deformed, the Gr/Mg2Si interface in the composite is easy to separate and become the crack propagation source. The Gr/Mg2Si interface should be avoided in the preparation of Gr/AlSi10Mg composite.

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