The generation of forces and moments on structures immersed in rarefied non-isothermal gas flows has received limited practical implementation since first being discovered over a century ago. formation significant thermal stresses requires both large gradients characteristic dimensions which are comparable to the molecular mean free path. For macroscopic geometries, this necessitates impractically high temperatures very low pressures. At microscale, however, these conditions easily achieved,...

Controlled ice nucleation is used in manufacturing of lyophilized pharmaceutical drugs, biologics and vaccines to improve consistency freezing, drying resulting quality stability across product batches. The rapid-depressurization-controlled (RD-CIN) based on fast expansion pressurant gas has been applied industry since the early 2000s, however, exact mechanism action remained obscure affecting its reliability, especially for small vials, large fill volumes large-scale lyophilizers. We...

Abstract This work presents a new user-friendly lyophilization simulation and process optimization tool, freely available under the name LyoPRONTO. tool comprises freezing primary drying calculators, design-space generator, optimizer. The calculator performs 0D lumped capacitance modeling to predict product temperature variation with time which shows reasonably good agreement experimental measurements. 1D heat mass transfer analysis in vial predicts an average deviation of 3% from...

Thermally driven gas flow is exploited in a microscale device for the purpose of pressure dependent actuation rarefied environments. The relies on in-plane motion shuttle mass response to Knudsen thermal forces. measured capacitively and magnitude used estimate ambient pressure. Combined with heating element resistance, these measurements, principle, enable simultaneous determination composition if constituents are known. Numerical simulations using direct simulation Monte Carlo carried out...

We present performance modeling and experimental validation of a novel MEMS vacuum gas sensor based on the Knudsen thermal force. Direct simulation Monte Carlo (DSMC) thermally-driven flow force measurements show non-monotonic dependence ambient pressure, peaking at number order unity. Combining pressure with monotonically varying heat transfer rate allows both species concentration to be determined if constituents are known. The DSMC also shows that gradients between shuttle heater induce...

Freeze-drying has been widely adopted in the manufacturing of biologics for producing vaccines and protein-based therapeutics that are highly unstable liquid form.Radiofrequency (RF)-assisted lyophilization can significantly accelerate drying by applying controllable volumetric heating.In this paper, we design, first time, a quasi-random field (qRF) system.The system demonstrates a) primary acceleration b) very high uniformity with two different types antennas at 8 GHz.Specifically,...

Complex and non-intuitive flow structures controlled only by thermal gradients can be observed in rarefied gas flows. A force of thermophoretic nature, often referred to as Knudsen or radiometric force, become dominant microflow applications. Microelectromechanical In-plane Radiometric Actuator (MIKRA) that exploits these forces has been developed tested at Purdue. Previous efforts used DSMC understand the MIKRA structure validate numerical modeling for simple gases. This work investigated...

Views Icon Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Twitter Facebook Reddit LinkedIn Tools Reprints and Permissions Cite Search Site Citation Alina A. Alexeenko, D. Strongrich, G. Cofer, Pikus, I. B. Sebastiao, S. Tholeti, Shivkumar; Microdevices enabled by rarefied flow phenomena. AIP Conf. Proc. 15 November 2016; 1786 (1): 080001. https://doi.org/10.1063/1.4967594 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley...

When the flow is sufficiently rarefied, a temperature gradient, for example, between two walls separated by few mean free paths, induces gas flow---an observation attributed to thermo-stress convection effects at microscale. The dynamics of overall process governed Boltzmann equation---an integro-differential equation describing evolution molecular distribution function in six-dimensional phase space---which models dilute behavior level accurately describe wide range phenomena. Approaches...

The capability of gas actuation using thermal gradients in a rarefied flow is demonstrated for arrays interdigitated hot and cold vanes. force acting on the vane array quantified microNewton torsional balance over range pressures between 3.8 mTorr to 900 mTorr. Simulations are carried out SPARTA direct simulation monte carlo software elucidate mechanisms governing production. Both experimental numerical results non-dimensionalized fitted linear least-squares method. These correlations...

CubeSats with compact, low-power attitude-control systems open up opportunities for deep-space missions as well cost-effective constellation-based satellites targeting remote sensing and communication applications. Film Evaporation MEMS Tunable Array (FEMTA) is a micropropulsion technology that employs thermally-controlled surface tension in microscale capillary vaporization of liquid water propellant. FEMTA thrusters generate tunable thrust on the order micro-newton thrust-to-power ratio...

We present experimental measurements and numerical simulations of convective heat transfer performance in the transitional rarefied regime for an isolated rectangular beam geometry. Experiments were performed using single crystalline silicon elements having width-to-thickness aspect ratios 8.5 17.4. Devices enclosed a vacuum chamber heated resistively DC power supply. A range pressures corresponding to Knudsen numbers between 0.096 43.2 terms device thickness swept, adjusting applied...

We show that the Knudsen thermal force generated by a thermally-induced flow over heated beam near colder wall could be amplified significantly thermoelectric heating. Bidirectional actuation is achieved switching polarity of device bias voltage. The measurements resulting forces at different rarefaction regimes, realized changing geometry and gas pressure, are done using torsional microbalance. repulsive or attractive between thermoelectrically cooled plate substrate shown to up an order...

The paper reports on the experimental studies targeting Knudsen forces silicon microcantilevers. devices were fabricated a Silicon-On-Insulator wafer with one end anchored to substrate. Measurements performed through direct external heating of underlying Device deflection was quantified using confocal microscopy, showing an increase in force magnitude for decreasing number. carried out at constant substrate temperature number being controlled directly via ambient pressure.