Investigation of micro and nanoscale surfaces replication using injection molding

Micro and nanoscale features have numerous applications in microfluidic devices, flexible patterning, MEMS devices. Among three approaches to replication of micro and nanoscale features, which are nanoimprint lithography, hot embossing, and injection or injection compression molding, injection molding offers inexpensive and high rate means to produce these products. For micro injection molding, tooling development and usage of wide range of materials are needed for specific applications. In this work, novel polymer-metal hybrid tooling and microstructured surfaces of flexible materials, thermoplastic elastomers, and application for superhydrophobic surfaces were investigated.;A novel polymer-metal hybrid tooling was created to facilitate injection molding of parts with micro and nanostructured surfaces. Selected polymer and metal layers used in the novel polymer-metal hybrid tooling were investigated for the their effect of the replication of microstrucured surfaces. The polymer-metal hybrid tooling exhibited good replication (i.e., deeper features and sharper feature edges) at lower mold and melt temperatures. Heat transfer analysis showed that the polymer-metal hybrid tooling retarded heat transfer better than the polymer-back nickel, leading to longer solidification times. Polyimide based hybrid tooling was less susceptible to compression during use. This tooling offers flexibility; enhanced replication with lower temperatures; and shorter cycle times without use of rapid heating techniques.;For thermoplastic elastomers, relationship between TPE properties and replication quality was performed using copolyester block copolymers (COPES) and polyether block amide copolymers (PEBAs) with a range of hardness and viscosity. Materials with a moderate hardness had the widest processing window and COPEs showed slightly wider processing windows than PEBAs. The depth of the molded micro features were slightly influenced by COPE and PEBA hardness, and the softer elastomers exhibited sharper edged features. Overall replication was also affected by hardness not viscosity. PEBAs also exhibited a tendency to adhere to the tooling surface, and so, was molded with lower mold temperatures.;For superhydrophobic surfaces, tooling with systematically-varied micro-sized holes were designed and fabricated. Molding trials were performed with two different flow rate polycarbonate and one moderately- hard thermoplastic elastomer. Flexible thermoplastic elastomers showed good replication, however, the polycarbonate exhibited poor replication regardless of flow rate and processing conditions. Materials, tooling, and processing conditions should be examined further for poor replications.