Microfluidic channels formed by collapse of soft stamp

Fabricating straight and robust micro- or nanofluidic channels with an adjustable cross-section area represents a challenge for conventional fabrication techniques. Recently, it was discovered that when a soft elastomeric stamp comes in contact with a stiff substrate under pressure, the extensive deformation may lead to various geometries of internal channels (pores) that are bounded by the stamp material. However, the mechanical principles behind this new technique are still fuzzy. We use finite-element simulations to study the detailed characteristics of channels that are self-assembled by the collapse of a compliant stamp. Side collapse and slide-buckling mechanisms are analyzed. The key parameters controlling the channel formation and those governing the pore geometrical shapes and dimensions are identified and correlated. Simplified theoretical models are established to predict the critical collapse stress, and these models show a good consistency with empirical results. We further propose a new technique for fabricating microfluidic channels with nearly circular profiles.