Uniform Thermal Nanoimprinting at Low Pressure by Improved Heat Transfer Using Hydrofluoroethers

Abstract

We propose a low-pressure process of thermal nanoimprinting by improved heat transfer. In poly(ethylene terephthalate) (PET; T g=75 °C), poly(methyl methacrylate) (PMMA; T g=105 °C), and polycarbonate (PC; T g=150 °C), in which fine pattern transfer can be performed at 12.9 MPa, if the imprinting pressure is reduced to one-third, poor transfer occurs at the edges of the patterned area, and the uniformity of the entire patterned area degrades. However, it turned out that moldability can be improved significantly by introducing hydrofluoroether (HFE) between the mold and the surface of thermoplastic sheets. A dispensing method using a pipette was chosen to introduce HFE, and three types of HFE liquid, namely, Novec 7100 (bp=61 °C), Novec 7200 (bp=76 °C), and Novec 7300 (bp=98 °C), were tested. It was confirmed that the uniformity was greatly improved by combinations of PET and Novec 7100, PMMA and Novec 7200, and PC and Novec 7300. The heat of the mold spread efficiently onto the surface of thermoplastics via the HFE liquid, and it seems to result in the same effect as a preliminary heating process before the mold comes into contact with the thermoplastic sheet.

Optimization of a continuous hot embossing process for fabrication of micropyramid structures in thermoplastic sheets

“…Commercially available 2mm thick PMMA sheets, which were sourced from Plastock UK, were used as the embossing substrate. The glass transition temperature was approximately 105°C 25,26 . Dimensional values of the embossed structures in all fabricated samples were measured by microscope imaging, before converting into a percentage of the original mold structure dimension, referred to as the 'fill factor %'.…”

Self-Extinguishing Lithium Ion Batteries Based on Internally Embedded Fire-Extinguishing Microcapsules with Temperature-Responsiveness

“…Here we suggest the use of temperature-responsive “self-extinguishing” microcapsules to achieve highly reliable safety of the cell and also maintain the desired electrochemical performance. Accelerating rate calorimetry (ARC) studies on LIBs have demonstrated that significant exothermic heat, which is produced by decomposition of the electrolyte and active material, accelerates thermal runaway through violent combustion reactions. − Upon this background, we successfully incorporated a commonly used extinguishing agent (1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)-pentane) (DMTP)) with remarkable endothermic properties (Δ H = +102.1 J g –1 ) , in an LIB to effectively suppress a drastic temperature rise. The extinguishing agent can be vaporized in a timely manner by the absorption of external heat and finally extinguishes the fire before the cell reaches a serious thermal runaway state.…”