Micromolding in capillaries: A study of wetting and spreading of liquids in rectangular capillaries and applications to materials science.

摘要

Micromolding in capillaries (MIMIC) is a technique of patterning a surface of a substrate with micrometer- and submicrometer-scale structures. An elastomeric mold made of poly(dimethylsiloxane) and having relief features in its surface is placed on a support, and contact between the elastomer and the substrate forms a network of interconnected channels. A fluid--a precursor to a polymer, a solution, or a suspension of the material to be patterned--fills these channels by capillary action. After the material in the fluid has crosslinked, crystallized, cured, adhered, or deposited onto the surface of the substrate, the elastomeric component is removed. The microstructures remain on the surface in the pattern complementary to that present in the mold.; In Chapter 2, MIMIC has been used to study the dynamics of imbibition of liquids in rectangular capillaries formed between the elastomeric mold and self-assembled monolayers (SAMs) of alkanethiolates on gold. The dynamic shapes of the liquids in capillaries, formed on SAMs having different interfacial free energies ({dollar}gammasb{lcub}rm sv{rcub}){dollar} are examined as crosslinked, solid polymers using microscopies. The shape of the imbibing liquid on a SAM with low {dollar}rmgammasb{lcub}sv{rcub}{dollar} involves precursor structures that precede macroscopic flow; on high {dollar}rmgammasb{lcub}sv{rcub}{dollar}, imbibition occurs without the precursor structures. Rates of capillary imbibition are linearly correlated to static advancing contact angles of liquids on different SAMs. Chapter 2 describes applications of MIMIC in fabrication of microstructures of organic polymers, inorganic and organic salts, ceramics, metals by electroless deposition, and crystalline arrays of microspheres. Chapter 3 examines the fabrication of polymeric structures and free-standing films fabricated from filling channels formed between two elastomeric masters, both of which had relief patterns on their surfaces. Chapter 4 describes the use of MIMIC in fabrication of patterned, crystalline arrays of polymeric microspheres and presents a mechanism that explains the process of crystallization.