Analyzing adhesion in microstructured systems through a robust computational approach

Abstract

Analyzing surface forces for myriad geometric structures facilitates the design of properties in interacting interfacial systems. Along these lines, we demonstrate a generalized technique that can be utilized to evaluate the orientation dependence of a particle interacting with multiple finite or semi‐infinite objects. Specifically, the surface element integration technique is modified to account for surface elements of a particle not directly adjacent to the object with which it is interacting; this facilitates the analysis of objects with finite shape and with arbitrary orientations. Furthermore, as a technology‐relevant proof‐of‐concept demonstration, the influence of van der Waals (vdW) forces on the performance and reliability of microstructured systems used for the collection of trace particles is reported. The importance of the location of the particle contact with the microstructure and the independence of vdW forces generated by each microstructure is demonstrated using the developed computational approach. Thus, the methodology presented here can ultimately be utilized for a variety of interfacial forces generated by nontrivial systems with heterogeneous properties in order to provide design motifs in a low‐cost, high‐throughput manner.

London-van der Waals Force Field of a Chemically Patterned Surface To Enable Selective Adhesion

“…Because the Hamaker constant of a material in a liquid medium is always lower than the same in air, the L-vdW forces at a solid–solid interface in a “liquid” environment would also be lower than the same in air. Further, this study does not consider the surface roughness of the interacting bodies to avoid the convolution of the morphological heterogeneity with the chemical heterogeneity; however, the discussed mathematical formulations along with various approaches to account for the surface roughness presented elsewhere ,− ,,, can be utilized to describe the contributions coming from the surface roughness in such systems. The results of this study are applicable to nonretarded L-vdW interactions.…”

“…The physical properties include the shape, size, and topography of the adhering bodies. Significant progress has been made in understanding and modeling the effects of the physical properties on the adhesion at the point of solid–solid contact, − as follows: The adhesion behavior is governed by the London-van der Waals (L-vdW) forces if particles and surfaces are in contact or very close to each other (separation distance < 15 nm) in dry environments. − ,− The L-vdW force arises because of induced dipole–induced dipole interactions which make the van der Waals forces ever-present in all systems. The L-vdW is a major part of the vdW-force, and it is identical to the vdW force for the case when the interacting surfaces are uncharged. The total particle–surface L-vdW force decreases as the particle size is decreased. − This is attributed to the reduced mass interacting in the vdW-active region. The topography of the interacting bodies can alter the L-vdW forces between them very significantly. − …”

“…The adhesion behavior is governed by the London-van der Waals (L-vdW) forces if particles and surfaces are in contact or very close to each other (separation distance < 15 nm) in dry environments. − ,− The L-vdW force arises because of induced dipole–induced dipole interactions which make the van der Waals forces ever-present in all systems. The L-vdW is a major part of the vdW-force, and it is identical to the vdW force for the case when the interacting surfaces are uncharged.…”

“…A particle approaching the chemical interfaces, as shown in Figure , will have different affinities toward different parts of the surface. After Hamaker’s work to determine the L-vdW forces for a smooth particle interacting with chemically homogeneous surfaces, many researchers have applied Hamaker’s additive approach to determine the L-vdW forces for particle–surface systems with varied physical parameters such as geometries, orientations, and surface morphologies. − ,, There are comparatively very few studies of the adhesion dynamics of a particle approaching a surface with different chemical interfaces. , A detailed understanding of particle adhesion to a chemical interface can be utilized to guide and manipulate the path lines of approaching particles (within the vdW region) to enable their selective adhesion in different applications.…”