Effect of the Thermal History on the Crystallinity of Poly (L-lactic Acid) During the Micromolding Process

Abstract

The micromolding process using biocompatible thermoplastic polymers is highly attractive as a fabrication process of microdevices in biomedical applications. In this study, we investigated the effect of the thermal history in the micromolding process on the crystallinity of semi-crystalline polymers, such as poly (L-lactic acid) (PLLA), during their crystallization from the amorphous and molten states. In particular, the thermal history in the micromolding process using poly(dimethylsiloxane) replica mold embedded with a thermocouple was recorded. The crystallinity of PLLA constructs fabricated using the micromolding process was measured via wide-angle X-ray scattering, and crystallization kinetics was analyzed based on the Kolmogorov–Johnson–Mehl–Avrami equation. A crystallization rate of k = 0.061 min−n was obtained in the micromolding process of PLLA crystallization from the amorphous state, accompanied by the quenching operation, forming a large number of crystal nuclei. Finally, the fabrication of PLLA microneedles was performed using micromolding processes with different thermal histories. The information about the thermal history during the micromolding process is significant in the development of polymer microdevices to achieve better material properties.

Latest Advancements in Micro Nano Molding Technologies—Process Developments and Optimization, Materials, Applications, Key Enabling Technologies

“…(4) Applications. Kim et al [9] presented the production of a miniaturized out-of-plane compliant bistable mechanism (OBM) via micro injection molding; Wu et al [10] reviewed the state of the art and perspectives on silicon waveguide crossings and discussed the use of polymers as vertical directional coupler materials; Cheng et al [11] reviewed the design and emerging trends of grating couplers on silicon photonics and presented the possibility of a polymer-based micro packaging application of plasmonic surfaces; Takehara et al [12] fabricated microneedle arrays in Poly (L-lactic Acid) via micro hot embossing/compression molding and studied the effect of the thermal history on the material crystallinity during the process.…”