Catheter thermal energy generation and temperature in rotational atherectomy.

This research studies the catheter friction thermal energy generation and saline temperature in rotational atherectomy (RA). RA is a catheter-based procedure utilizing a high-speed (typically 130,000 to 210,000 rpm) miniature grinding wheel to remove hardened calcified plaque inside the artery to restore the blood flow. During RA, elevated temperature due to the friction within the catheter may lead to complications such as slow-flow/no-reflow and myocardial infarction. RA experiments were conducted to measure the catheter temperature. An advection-diffusion model with inverse heat transfer solution was developed to estimate the spatial and temporal distributions of saline temperature and study effects of the rotational speed, catheter insertion length, and flow rates of blood-mimicking water and saline. The saline temperature rise is higher with higher wheel rotational speed, shorter insertion length, and lower flow rates of blood-mimicking water and saline. The wheel rotational speed and blood flow rate are the two most significant parameters affecting the saline and blood-mimicking water mixture temperature, which exhibits the highest (9 °C) rise under the 175,000 rpm wheel rotational speed and no blood-mimicking water flow (totally occluded artery) condition. This research provides insights and guidelines on RA device and clinical procedure from the thermal perspective.

A split-optimization approach for obtaining multiple solutions in single-objective process parameter optimization.

It can be observed from the experimental data of different processes that different process parameter combinations can lead to the same performance indicators, but during the optimization of process parameters, using current techniques, only one of these combinations can be found when a given objective function is specified. The combination of process parameters obtained after optimization may not always be applicable in actual production or may lead to undesired experimental conditions. In this paper, a split-optimization approach is proposed for obtaining multiple solutions in a single-objective process parameter optimization problem. This is accomplished by splitting the original search space into smaller sub-search spaces and using GA in each sub-search space to optimize the process parameters. Two different methods, i.e., cluster centers and hill and valley splitting strategy, were used to split the original search space, and their efficiency was measured against a method in which the original search space is split into equal smaller sub-search spaces. The proposed approach was used to obtain multiple optimal process parameter combinations for electrochemical micro-machining. The result obtained from the case study showed that the cluster centers and hill and valley splitting strategies were more efficient in splitting the original search space than the method in which the original search space is divided into smaller equal sub-search spaces.

A planar PDMS micropump using in-contact minimized-leakage check valves.

We present a micropump with a simple planar design featuring compliant in-contact check valves in a single layer, which allows for a simple structure and easy system integration. The micropump, based on poly(dimethylsiloxane) (PDMS), primarily consists of a pneumatically driven thin membrane, a pump chamber, and two in-plane check valves. The pair of check valves is based on an in-contact flap-stopper configuration and is able to minimize leakage flow, greatly enhancing the reliability and performance of the micropump. Systematic experimental characterization of the micropump has been performed in terms of the frequency response of the pumping flow rate with respect to factors including device geometry (e.g. chamber height) and operating parameters (e.g. pneumatic driving pressure and backpressure). The results demonstrate that this micropump is capable of reliably generating a maximum flow rate of 41 µL min-1 and operating against a high backpressure of up to 25 kPa. In addition, a lumped-parameter theoretical model for the planar micropump is also developed for accurate analysis of the device behavior. These results demonstrate the capability of this micropump for diverse applications in lab-on-a-chip systems.