Deformation of Pyramidal PDMS Stamps During Microcontact Printing

Abstract

Microcontact printing (MicroCP) is a form of soft lithography that uses the relief patterns on a master polydimethylsiloxane (PDMS) stamp to form patterns of self-assembled monolayers (SAMs) of ink on the surface of a substrate through conformal contact. Pyramidal PDMS stamps have received a lot of attention in the research community in recent years, due to the fact that the use of the pyramidal architecture has multiple advantages over traditional rectangular and cylindrical PDMS stamps. To better understand the dynamic MicroCP process involving pyramidal PDMS stamps, in this paper, numerical studies on frictionless adhesive contact between pyramidal PDMS stamps and transversely isotropic materials are presented. We use a numerical simulation method in which the adhesive interactions are represented by an interaction potential and the surface deformations are coupled by using half-space Green's functions discretized on the surface. It shows that for pyramidal PDMS stamps, the contact area increases significantly with increasing applied load, and thus, this technique is expected to provide a simple, efficient, and low-cost method to create variable two-dimensional arrays of dot chemical patterns for nanotechnology and biotechnology applications. The DMT-type and Johnson–Kendall–Roberts (JKR)-type-to-DMT-type transition regimes have been explored by conducting the simulations using smaller values of Tabor parameters.

Fabrication of Tapered 3D Microstructure Arrays Using Dual-Exposure Lithography (DEL)

“…With the application of weight on the substrate, the tips of the microstructures tend to collapse a little. Factors affecting the microstructure collapse are beyond the scope of this work, but they can be referred to in a previous study [ 2 ].…”

“…A three-dimensional microstructure array (3D-MSA) comprises a large number of micro-structured shapes (e.g., cylindrical [ 1 ], cone [ 2 ], hemispherical [ 3 ], and trapezoidal [ 4 ]), arranged in a defined pattern [ 5 ]. MSAs, with these micron-sized (~1–15 microns) structural units, bestow unique tunable material properties, such as wettability, optical characteristics, and cell adhesion [ 6 , 7 , 8 ].…”

“…MSAs, with these micron-sized (~1–15 microns) structural units, bestow unique tunable material properties, such as wettability, optical characteristics, and cell adhesion [ 6 , 7 , 8 ]. These MSAs have been widely employed in studies like anti-wetting surfaces [ 9 ], optical waveguide fabrication [ 10 ], cell mechanics studies [ 11 ], stem cell engineering [ 12 ], and other scientific material applications [ 2 , 13 ]. MSA applications also include structural support in the fabrication of microelectrode array for brain interface studies [ 14 , 15 ], microprobes for neural depth recordings [ 16 , 17 ], microneedles for drug delivery [ 18 ], and other micro-optic studies [ 19 , 20 ].…”

Investigations on the Adhesive Contact Behaviors between a Viscoelastic Stamp and a Transferred Element in Microtransfer Printing

“…On one hand, this material owns both the elasticity of a solid and the viscosity of a liquid, that is the viscoelastic property. Due to this property, the viscoelastic material is sensitive to changes in its pulling velocity and preload [2,7,8] and, as a result, the reasonable control of these two parameters becomes one of the difficulties in improving the transfer printing yield. On the other hand, the mixing ratio of the base polymer to the curing agent during preparation of PDMS has a significant effect on its work of adhesion [9].…”