Showing papers by "Daniel J. Preston published in 2020"

A Predictive Model of the Temperature-Dependent Inactivation of Coronaviruses

Abstract: The COVID-19 pandemic has stressed healthcare systems and supply lines, forcing medical doctors to risk infection by decontaminating and reusing single-use personal protective equipment. The uncertain future of the pandemic is compounded by limited data on the ability of the responsible virus, SARS-CoV-2, to survive across various climates, preventing epidemiologists from accurately modeling its spread. However, a detailed thermodynamic analysis of experimental data on the inactivation of SARS-CoV-2 and related coronaviruses can enable a fundamental understanding of their thermal degradation that will help model the COVID-19 pandemic and mitigate future outbreaks. This work introduces a thermodynamic model that synthesizes existing data into an analytical framework built on first principles, including the rate law for a first-order reaction and the Arrhenius equation, to accurately predict the temperature-dependent inactivation of coronaviruses. The model provides much-needed thermal decontamination guidelines for personal protective equipment, including masks. For example, at 70 °C, a 3-log (99.9%) reduction in virus concentration can be achieved, on average, in 3 min (under the same conditions, a more conservative decontamination time of 39 min represents the upper limit of a 95% interval) and can be performed in most home ovens without reducing the efficacy of typical N95 masks as shown in recent experimental reports. This model will also allow for epidemiologists to incorporate the lifetime of SARS-CoV-2 as a continuous function of environmental temperature into models forecasting the spread of the pandemic across different climates and seasons.

Polymer Infused Porous Surfaces for Robust, Thermally Conductive, Self-Healing Coatings for Dropwise Condensation

Abstract: Hydrophobic coatings with low thermal resistance promise a significant enhancement in condensation heat transfer performance by promoting dropwise condensation in applications including power generation, water treatment, and thermal management of high-performance electronics. However, after nearly a century of research, coatings with adequate robustness remain elusive due to the extreme environments within many condensers and strict design requirements needed to achieve enhancement. In this work, we enable long-lasting condensation heat transfer enhancement via dropwise condensation by infusing a hydrophobic polymer, Teflon AF, into a porous nanostructured surface. This polymer infused porous surface (PIPS) uses the large surface area of the nanostructures to enhance polymer adhesion, while the nanostructures form a percolated network of high thermal conductivity material throughout the polymer and drastically reduce the thermal resistance of the composite. We demonstrate over 700% enhancement in the condensation of steam compared to an uncoated surface. This performance enhancement was sustained for more than 200 days without significant degradation. Furthermore, we show that the surfaces are self-repairing upon raising the temperature past the melting point of the polymer, allowing recovery of hydrophobicity and offering a level of durability more appropriate for industrial applications.

Smart Thermally Actuating Textiles

Abstract: Biologically inspired actuators made from soft materials are innately compliant, adaptable to their environment, and able to perform biomimetic motions;[1–4] as such, they are ideal for devices that interact with humans, including wearable robots.[5–7] The majority of current soft robots rely on a pressurized fluid delivered via tether and require hardware (e.g., pumps and valves) to supply the fluid and control its flow. This hardware, which can often be heavy, noisy, and bulky,[1,2] prevents the realization of lightweight and portable wearable devices, especially for applications requiring multiple actuator arrays because the number of valves and pneumatic lines scales with the number of actuators. This can pose a challenge for the development of soft robotic devices that require multiple controlled actuators, such as wearable robots to assist multiple-degree-of-freedom limb movement for assistance[7] or rehabilitation[6] or active pressure modulation devices for prevention of pressure sores or mechanotherapy applications.[8] To remove the need for a pressurized fluid supply, researchers have developed alternative electrically and thermally activated soft actuator technologies including shape memory polymers,[9,10] piezopolymers,[11] electrostatic actuators,[12,13] chargeinjection electrohydrodynamic devices,[14] electrolysis-based actuators,[15] and encapsulated electromagnetic systems.[16] Building upon this work, researchers have translated untethered soft actuator designs to textiles when considering wearable applications, motivated by the prevalence of textiles as the base material for the vast majority of soft goods and clothing. Every day we intimately interact with textiles because they are lightweight, conformal (compared to molded and printed elastomeric systems), and robust to repeated, sometimes violent, stresses and abrasions encountered during use (compared to polymer films). The hierarchical nature of textiles provides the opportunity to create soft robotic systems for wearable devices through the integration of smart fibers that can sense or actuate by electrical or chemical means.[17,18] Textile systems that can apply force, change shape, or modulate stiffness have been achieved through the integration of shape-memory alloys (SMAs) as fibers into the textile structure.[19,20] Other textile actuation approaches include thermally actuated coiled Soft robots have attracted attention for biomedical and consumer devices. However, most of these robots are pneumatically actuated, requiring a tether and thus limiting wearable applications that require multiple controlled actuators. By pairing liquid-vapor phase change actuation with a textile-based laminated manufacturing method, smart thermally actuating textiles (STATs) eliminate the need for a pneumatic tether. STATs are lightweight and unobtrusive for wearable applications and exploit a facile manufacturing approach that supports arbitrary customization of the form factor and easy creation of connected arrays of individual robotic modules. Through integrated sensing and heating elements, STATs demonstrate closed-loop feedback that enables dynamic pressure control in the presence of environmental temperature fluctuations.

Analysis of Powders Containing Illicit Drugs Using Magnetic Levitation

Abstract: Magneto-Archimedes levitation (MagLev) enables the separation of powdered mixtures of illicit drugs (cocaine, methamphetamine, heroin, fentanyl, and its analogues), adulterants, and diluents based on density, and allows the presumptive identification of individual components. Small samples (mass <50 mg), with low concentrations of illicit drugs, present a particular challenge to analysis for forensic chemists. The MagLev device, a cuvette containing a solution of paramagnetic gadolinium(III) chelate in a non-polar solvent, placed between two like-poles-facing NdFeB magnets, allowed separation of seven relevant compounds simultaneously. In particular, initial separation with MagLev, followed by characterization by FTIR-ATR, enabled identification of fentanyl in a sample of fentanyl-laced heroin (1.3 wt % fentanyl, 2.6 wt % heroin, and 96.1 wt % lactose). MagLev allows identification of unknown powders in mixtures and enables confirmatory identification based on structure-specific techniques.

Effects of airborne hydrocarbon adsorption on pool boiling heat transfer

Abstract: During pool boiling, a significantly high heat flux leads to the transition from nucleate boiling to film boiling, where a vapor film forms over the boiling surface, drastically increasing thermal resistance This transition at the critical heat flux (CHF) results in an abrupt increase in surface temperature and can lead to catastrophic failure of the boiler However, reported CHF values vary greatly, even for smooth surfaces of the same material; for example, the CHF values on flat silicon and silicon dioxide surfaces vary across studies by up to 49% and 84%, respectively Here, we address this discrepancy by accounting for hydrocarbon adsorption on boiling surface Hydrocarbon adsorption on smooth boiling surfaces decreases surface wettability, hindering the ability to maintain liquid contact with the surface and, thus, lowering the pool boiling CHF To investigate hydrocarbon adsorption kinetics under ambient conditions and the subsequent effect on CHF, we cleaned flat silicon dioxide samples with argon plasma to remove hydrocarbon contaminants and then exposed them to laboratory air for different periods of time before conducting pool boiling experiments Pool boiling results along with x-ray photoelectron spectroscopy data showed that the amount of adsorbed hydrocarbon increased with exposure time in air, which resulted in a decrease in wettability and, accordingly, a decrease in CHF This work has important implications for understanding the spread in CHF values reported in the literature and may serve as a guideline for the preparation of boiling surfaces to achieve consistent experimental results

Soft Non-Volatile Memory for Non-Electronic Information Storage in Soft Robots

Abstract: Pneumatically operated soft robots require complex infrastructure for their operation: microcontrollers must control hard pneumatic valves via power electronics. Although soft digital logic gates based on soft valves have been demonstrated as a replacement for electronic control, the development of memory from logic gates is cumbersome (three logic gates with mono-stable membranes for the development of a single S-R latch), and such memory is only capable of holding, but not storing, information; after a power reset, the membranes relax to their idle states, and the information is lost. In this work, we introduce a soft memory device with a bistable membrane that allows the permanent storage of binary information in soft materials, and we demonstrate its writing and erasing operations. We also introduce a new type of pneumatically-driven soft display, the soft bubble display. We connect the display to our soft memory device to visualize the information that is held in the memory. Our work highlights the importance of material-based memory and its future use for programming soft robots.

Heat transfer suppression by suspended droplets on microstructured surfaces

Abstract: Manipulating the degree of droplet contact with a surface significantly impacts applications involving drag reduction, corrosion inhibition, droplet transportation, and thermal management. Extensive studies have been conducted to study droplet wetting behavior on plain and micro/nanostructured surfaces, with a particular focus in the recent literature on heated surfaces, where evaporation beneath the droplet impacts the apparent wettability. In previous literature, the peak droplet lifetime and minimum heat transfer on heated surfaces were observed at the Leidenfrost point. In this study, however, we report the existence of two distinct peaks for droplet lifetime on heated surfaces structured with silicon micropillar arrays. Initially, droplets exhibit complete wetting at low surface temperatures, but as surface temperature increases, the wetting state transitions first to a contact non-wetting state (i.e., a Cassie–Baxter-like state) and then to the non-contact Leidenfrost state; two distinct local maxima in droplet lifetime are observed, one corresponding to each transition. The contact non-wetting transition temperature and Leidenfrost point increase with larger micropillar pitch and taller height, which we attribute primarily to the resulting lower effective thermal conductivity of the micropillar array beneath the droplets, in agreement with the analytical force-balance-based modeling. This study provides a comprehensive investigation of the effect of surface structuring on contact non-wetting and Leidenfrost phenomena and will serve as design guidelines in controlling the contact non-wetting and Leidenfrost temperatures for specific applications.

A Predictive Model of the Temperature-Dependent Inactivation of Coronaviruses

Abstract: The COVID-19 pandemic has stressed healthcare systems and supply lines, forcing medical doctors to risk infection by decontaminating and reusing single-use medical personal protective equipment. The uncertain future of the pandemic is compounded by limited data on the ability of the responsible virus, SARS-CoV-2, to survive across various climates, preventing epidemiologists from accurately modeling its spread. However, a detailed thermodynamic analysis of experimental data on the inactivation of SARS-CoV-2 and related coronaviruses can enable a fundamental understanding of their thermal degradation that will help model the COVID-19 pandemic and mitigate future outbreaks. This paper introduces a thermodynamic model that synthesizes existing data into an analytical framework built on first principles, including the rate law and the Arrhenius equation, to accurately predict the temperature-dependent inactivation of coronaviruses. The model provides much-needed thermal decontamination guidelines for personal protective equipment, including masks. For example, at 70 °C, a 3-log (99.9%) reduction in virus concentration can be achieved in ≈ 3 minutes and can be performed in most home ovens without reducing the efficacy of typical N95 masks. The model will also allow for epidemiologists to incorporate the lifetime of SARS-CoV-2 as a continuous function of environmental temperature into models forecasting the spread of coronaviruses across different climates and seasons.

Système de lévitation magnétique

Abstract: L'invention concerne un systeme de levitation magnetique, lequel systeme comprend un premier et un second aimants ayant des surfaces de leurs poles identiques qui se font face ; et un recipient dispose entre les premier et second poles du type magnetique et contenant une solution comprenant un complexe paramagnetique dans un solvant non aqueux, le complexe paramagnetique comprenant un metal paramagnetique et au moins un ligand qui se coordonne au metal paramagnetique par l'intermediaire d'un don d'electrons. L'invention concerne egalement des procedes de separation d'un melange de composes solides, et/ou d'identification, de confirmation et/ou de prevision de la composition du melange.

Magnetic levitation system

Abstract: A magnetic levitation system is described, including a first and second magnets having surfaces of their like-poles facing each other; and a container disposed between the first and second magnets' like poles and containing a solution including a paramagnetic complex in a non-aqueous solvent, where the paramagnetic complex includes a paramagnetic metal and at least one ligand that coordinates to the paramagnetic metal via electron donation. Methods of separating a mixture of solid compounds, and/or identifying, confirming, and/or predicting the composition of the mixture, are also described.