MEMS Wireless Sensor Networks for Spacecraft and Vacuum Technology
thesisposted on 06.05.2021, 15:03 by Andrew Strongrich
Wireless sensor networks are highly integrated across numerous industries from industrial
manufacturing to personal health monitoring. They provide several key benefits over
traditional wired systems including positioning flexibility, modularity, interconnectivity, and
robust data routing schemes. However, their adoption into certain sectors such as vacuum
and aerospace has been slow due to tight regulation, data security concerns, and device
Lyophilization is a desiccation technique used to stabilize sensitive food and drug products
using vacuum sublimation. A series of wireless devices based on the Pirani architecture are
developed to quantify the spatial variations in pressure and temperature throughout this
process. The data is coupled to computational fluid dynamics simulations to estimate the
sublimation rate over time. This information is then used to quantify the heat and mass
transfer characteristics of the product, allowing estimates of product temperature and mass
flux to be obtained for an arbitrary cycle. This capability is significant, having the ability
to accelerate process development and reduce manufacturing time.
Drying performance during lyophilization is highly sensitive to the dynamics of the freezing
process. This work therefore also develops a wireless network to monitor both gas
pressure and temperature throughout the controlled ice nucleation process, a technique used
to improve batch uniformity by inducing simultaneous and widespread ice nucleation via
adiabatic decompression. The effects of initial charge pressure, ballast composition, and vial
size are investigated. Experimental data is supported by numerical modeling to describe the
evolution of the true gas temperature during the discharge event.
Finally, The mechanisms governing the lyophilization process are directly applied to the
aerospace industry in the form of a novel milliNewton-class evaporation-based thruster concept.
The device was tested under vacuum using a torsional balance and demonstrated peak
thrust magnitudes on the order of 0.5 mN. A state observer model was then implemented
to decouple the dynamics of the balance with the time-dependent thrust input. With this
model the true time-dependent thrust output and corresponding thruster performance are
PFI-RP: Sensors, Computational Modeling, and Bioanalytical Technologies for Closed-Loop Lyophilization
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