Abstract
We demonstrate the demolding of topologically complex three-dimensional elastomeric microstructures from a femtosecond laser micromachined glass substrate. Demolding success rates of >90% are achieved, which are qualitatively supported by a simple mechanical model.
Highlights
The creation of three-dimensional microscaled features on surfaces has many applications, including the control of surface properties such as adhesion [1] and wettability, as well as for fabricating microfluidic, optofluidic, or micromechanical devices
We model the stress at the point of highest deformation, when the narrow-diameter section of the PDMS is stretched around the wider-diameter section of the glass
The loading is a combination of the hoop and friction forces resisting the demolding, for which we evaluate the equivalent von Mises stress and compare that to the ultimate tensile strength of PDMS
Summary
The creation of three-dimensional microscaled features on surfaces has many applications, including the control of surface properties such as adhesion [1] and wettability, as well as for fabricating microfluidic, optofluidic, or micromechanical devices. The nonlinear multiphoton absorption process locally modifies (but does not ablate) the material in a micron-scaled laser-affected volume; in this volume, the local etching rate in hydrofluoric acid is increased compared to the pristine material. We use this process to fabricate monolithic glass (fused silica) micromolds with complex three-dimensional surface topology, and demonstrate the replication of the negative structures with polydimethylsiloxane (PDMS). The molding process allows many copies of one machined surface to be produced at a low cost, overcoming the limitations of the serial mold fabrication process
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