Mesoscale Simulation Based on the Dynamic Mean-Field Density Functional Method on Block-Copolymeric Ionomers for Polymer Electrolyte Membranes.

Block copolymers generally have peculiar morphological characteristics, such as strong phase separation. They have been actively applied to polymer electrolyte membranes for proton exchange membrane fuel cells (PEMFCs) to obtain well-defined hydrophilic regions and water channels as a proton pathway. Although molecular simulation tools are advantageous to investigate the mechanism of water channel formation based on the chemical structure and property relationships, classical molecular dynamics simulation has limitations regarding the model size and time scale, and these issues need to be addressed. In this study, we investigated the morphology of sulfonated block copolymers synthesized for PEM applications using a mesoscale simulation based on the dynamic mean-field density functional method, widely applied to investigate macroscopic systems such as polymer blends, micelles, and multi-block/grafting copolymers. Despite the similar solubility parameters of the monomers in our block-copolymer models, very different morphologies in our 3D mesoscale models were obtained. The model with sulfonated monomers, in which the number of sulfonic acid groups is twice that of the other model, showed better phase separation and water channel formation, despite the short length of its hydrophilic block. In conclusion, this unexpected behavior indicates that the role of water molecules is important in making PEM mesoscale models well-equilibrated in the mesoscale simulation, which results in the strong phase separation between hydrophilic and hydrophobic regions and the ensuing well-defined water channel. PEM synthesis supports the conclusion that using the sulfonated monomers with a high sulfonation degree (32.5 mS/cm) will be more effective than using the long hydrophilic block with a low sulfonation degree (25.2 mS/cm).

Development of an intrafascicular neural interface for peripheral nerve implantation.

This paper describes an intrafascicular neural interface for peripheral nerve implantation. The flexible penetrating microelectrode array with varying lengths (vl-FPMA), interconnection cable, wireless recording and stimulator modules were designed and fabricated to detect neural signals from the peripheral nerves or to stimulate them. The vl-FPMA consisted of silicon needles and polydimethylsiloxane (PDMS) platform supporting the needles. The length of electrode needles varied from 600 to 1000 µm. The interconnection cable was fabricated as parylene-metal-parylene sandwiched structure. The wireless recording/stimulation modules were also developed and connected with the electrodes. The integrated system was implanted in the sciatic nerve of beagles and the recording capability of the integrated system was demonstrated successfully.

Effect of implant drill characteristics on heat generation in osteotomy sites: a pilot study.

OBJECTIVES: The objective of this study was to evaluate the effect of drill-bone contact area on bone temperature during osteotomy preparation. MATERIAL AND METHODS: Conventional triflute Ø3.6 mm drills were modified with the intent to reduce frictional heat induction. The peripheral dimensions of the drill were reduced 0.15, 0.35 and 0.5 mm to evaluate the effect of surface area on induction of frictional heat between the drill and bone/cutting debris (parameter A). Also, the lateral cutting surface of the drill was set to 0.1, 2 and 7.5 mm to estimate heat induced by direct function of the drill (parameter B). A non-modified triflute drill (parameter A: 0 mm; parameter B: 15 mm) served as control. Thus, nine drills with different A/B combinations vs. one control were tested in artificial bone. Real-time temperature changes (during drilling and withdrawing) were assessed using an infrared thermal imager. Each drilling procedure was performed up to 20 times. Thermal image data were transferred to a PC for simultaneous analysis. RESULTS: Mean temperature changes for all modified drill combinations were smaller than for the control (P<0.001). The effects of parameters A and B were statistically significant (P<0.001). There was a significant interaction effect between the two parameters (P<0.001) showing that the effect of parameter A on the mean temperature changes is different depending on the values of parameter B. As the dimensions of parameter B decreased, the temperature change during drilling also decreased. However, a tendency for the temperature to increase or decrease by parameter A was not observed. CONCLUSIONS: Within the limitations of this pilot study, the observations herein suggest that reduction in contact area between the drill and bone reduces heat induction. Further studies to optimize drill/bone contact dimensions are needed.