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To address the challenges of biopsy and intratumoral drug delivery using microdevices, a miniature multifunctional tethered device that has tissue cutting, biopsy and drug delivery capabilities is presented in this paper. The cutting module in the prototype is hydraulically powered and has an outside diameter (OD) of 2 mm at the tip and a cutter attached to 500 µm drive shaft. The hydraulic micromotor prototype was fabricated using micro additive manufacturing. It was tested using a benchtop set-up and had an average speed greater than 100,000 RPM at a water flowrate of 45 mL/min and a speed of about 34,000 RPM at 15 mL/min flowrate. This micromotor design was numerically modeled using 3D-transient simulations in ANSYS CFX to determine its performance characteristics and internal resistance. Preliminary testing was performed using cutting modules with five cutter geometries on agar tissue phantoms of different concentrations and other biological materials. The dissection ability of the cutting module, its ability to deliver particles, and collect biopsy samples were successfully demonstrated. Scaling the 2 mm OD device further, a 1 mm OD micromotor, with a nominal output shaft diameter of 250 µm, was fabricated and operated with air establishing the proof of concept. [ABSTRACT FROM AUTHOR]

A fundamental understanding of the evaporation/condensation phenomena is vital to many fields of science and engineering, yet there is many discrepancies in the usage of phase-change models and associated coefficients. First, a brief review of the kinetic theory of phase change is provided, and the mass accommodation coefficient (MAC, α) and its inconsistent definitions are discussed. The discussion focuses on the departure from equilibrium; represented as a macroscopic "drift" velocity. Then, a continuous flow, phase change driven molecular-dynamics setup is used to investigate steady-state condensation at a flat liquid-vapor interface of argon at various phase-change rates and temperatures to elucidate the effect of equilibrium departure. MAC is computed directly from the kinetic theory-based Hertz–Knudsen (H-K) and Schrage (exact and approximate) expressions without the need for a priori physical definitions, ad-hoc particle injection/removal, or particle counting. MAC values determined from the approximate and exact Schrage expressions ( α a p p S c h r a g e and α e x a c t S c h r a g e ) are between 0.8 and 0.9, while MAC values from the H-K expression ( α H − K ) are above unity for all cases tested. α e x a c t S c h r a g e yield value closest to the results from transition state theory [J Chem Phys, 118, 1392–1399 (2003)]. The departure from equilibrium does not affect the value of α e x a c t S c h r a g e but causes α H − K to vary drastically emphasizing the importance of a drift velocity correction. Additionally, equilibrium departure causes a nonuniform distribution in vapor properties. At the condensing interface, a local rise in vapor temperature and a drop in vapor density is observed when compared with the corresponding bulk values. When the deviation from bulk values are taken into account, all values of MAC including α e x a c t S c h r a g e show a small yet noticeable difference that is both temperature and phase-change rate dependent. [ABSTRACT FROM AUTHOR]

An abstract of the article "Contact Angle Measurement of Liquid Hydrogen (LH2) in Stainless Steel and Aluminum Cells" by Kishan Bellur and colleagues is presented.