Browsing by Author "Preston, Daniel J."
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Item A low-cost wearable device for portable sequential compression therapy(Frontiers Media S.A., 2022) Schara, Mark; Zeng, Mingde; Jumet, Barclay; Preston, Daniel J.In 2020, cardiovascular diseases resulted in 25% of unnatural deaths in the United States. Treatment with long-term administration of medication can adversely affect other organs, and surgeries such as coronary artery grafts are risky. Meanwhile, sequential compression therapy (SCT) offers a low-risk alternative, but is currently expensive and unwieldy, and often requires the patient to be immobilized during administration. Here, we present a low-cost wearable device to administer SCT, constructed using a stacked lamination fabrication approach. Expanding on concepts from the field of soft robotics, textile sheets are thermally bonded to form pneumatic actuators, which are controlled by an inconspicuous and tetherless electronic onboard supply of pressurized air. Our open-source, low-profile, and lightweight (140 g) device costs $62, less than one-third the cost the least expensive alternative and one-half the weight of lightest alternative approved by the US Food and Drug Administration (FDA), presenting the opportunity to more effectively provide SCT to socioeconomically disadvantaged individuals. Furthermore, our textile-stacking method, inspired by conventional fabrication methods from the apparel industry, along with the lightweight fabrics used, allows the device to be worn more comfortably than other SCT devices. By reducing physical and financial encumbrances, the device presented in this work may better enable patients to treat cardiovascular diseases and aid in recovery from cardiac surgeries.Item A predictive model of the temperature-dependent inactivation of coronaviruses(AIP, 2020) Yap, Te Faye; Liu, Zhen; Shveda, Rachel A.; Preston, Daniel J.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.Item A Soft Textile-Based System to Harvest Walking Energy for Rehabilitative and Assistive Devices(2021-04-28) Shveda, Rachel A.; Preston, Daniel J.Wearable assistive, rehabilitative, and augmentative devices require bulky and heavy power supplies, often making these tools more of a burden than an asset. This work demonstrates a soft, low-profile, and comfortable textile-based energy harvesting system. Pneumatic energy is harvested with a textile device integrated into a shoe insole, and pneumatic energy is stored in a flexible textile wearable, enabling users to produce and store the power needed to operate a range of pneumatic actuators. A maximum average power of nearly 3 W with a remarkably high efficiency (recovering more than 20% of the mechanical energy expended during walking) was harvested. The system was fabricated using a state-of-the-art stacked laminate assembly of textiles. To optimize our system, a mechano-fluidic model was developed and validated against experimental results. The use of our system is demonstrated in powering a textile-based assistive device as well as a supernumerary arm used to augment human capability.Item A wearable textile-based pneumatic energy harvesting system for assistive robotics(AAAS, 2022) Shveda, Rachel A.; Rajappan, Anoop; Yap, Te Faye; Liu, Zhen; Bell, Marquise D.; Jumet, Barclay; Sanchez, Vanessa; Preston, Daniel J.Wearable assistive, rehabilitative, and augmentative devices currently require bulky power supplies, often making these tools more of a burden than an asset. This work introduces a soft, low-profile, textile-based pneumatic energy harvesting system that extracts power directly from the foot strike of a user during walking. Energy is harvested with a textile pump integrated into the insole of the user’s shoe and stored in a wearable textile bladder to operate pneumatic actuators on demand, with system performance optimized based on a mechano-fluidic model. The system recovered a maximum average power of nearly 3 W with over 20% conversion efficiency—outperforming electromagnetic, piezoelectric, and triboelectric alternatives—and was used to power a wearable arm-lift device that assists shoulder motion and a supernumerary robotic arm, demonstrating its capability as a lightweight, low-cost, and comfortable solution to support adults with upper body functional limitations in activities of daily living.Item Conversion of Layered WS2 Crystals into Mixed-Domain Electrochemical Catalysts by Plasma-Assisted Surface Reconstruction(Wiley, 2024) Park, Jiheon; Cho, Iaan; Jeon, Hotae; Lee, Youjin; Zhang, Jian; Lee, Dongwook; Cho, Min Kyung; Preston, Daniel J.; Shong, Bonggeun; Kim, In Soo; Lee, Won-KyuElectrocatalytic water splitting is crucial to generate clean hydrogen fuel, but implementation at an industrial scale remains limited due to dependence on expensive platinum (Pt)-based electrocatalysts. Here, an all-dry process to transform electrochemically inert bulk WS2 into a multidomain electrochemical catalyst that enables scalable and cost-effective implementation of the hydrogen evolution reaction (HER) in water electrolysis is reported. Direct dry transfer of WS2 flakes to a gold thin film deposited on a silicon substrate provides a general platform to produce the working electrodes for HER with tunable charge transfer resistance. By treating the mechanically exfoliated WS2 with sequential Ar-O2 plasma, mixed domains of WS2, WO3, and tungsten oxysulfide form on the surfaces of the flakes, which gives rise to a superior HER with much greater long-term stability and steady-state activity compared to Pt. Using density functional theory, ultraefficient atomic sites formed on the constituent nanodomains are identified, and the quantification of atomic-scale reactivities and resulting HER activities fully support the experimental observations.Item Motion and Sash Height (MASH) alarms for efficient fume hood use(Springer Nature, 2021) Kongoletos, Johnathan; Munden, Ethan; Ballew, Jennifer; Preston, Daniel J.Ventilation, including fume hoods, consumes 40–70% of the total energy used by modern laboratories. Energy-conscious fume hood usage—for example, closing the sash when a hood is unused—can significantly reduce energy expenditures due to ventilation. Prior approaches to promote such behaviors among lab users have primarily relied on passive feedback methods. In this work, we developed a low-cost fume hood monitoring device with active feedback to alert lab users when a fume hood is left open and unused. Using data collected by the building management system, we observed a 75.6% decrease in the average sash height after installation of these “Motion and Sash Height” (MASH) alarms, which would result in a reduction roughly equal to 43% of the annual carbon emissions of a typical American vehicle, for each fume hood. The MASH alarm presented here reduced energy costs by approximately $1,159 per year, per hood, at MIT.Item Embargo Multiplexed Inertial Coalescence Filters(2023-09-08) Rasheed, Rawand Muzafar; Preston, Daniel J.Multiphase flows pose challenges to the design of efficient and reliable engineered systems including separators, liquid-gas chemical reactors, and thermofluidic devices. This thesis introduces a novel filtration method, called the multiplexed inertial coalescence filter, composed of parallel helical pathways designed to capture fine droplets and particles (< 30 µm) through inertial separation while maintaining a low pressure drop (< 200 Pa). Three main contributions of these filters are explored to showcase their versatility: (i) filtration of liquid droplets, (ii) filtration of solid particles, and (iii) use in transformative applications for high surface area reactors. Filtration efficiencies for 7 µm and 30 µm droplets are characterized for varying flow conditions, and models for the filtration efficiency and pressure drop were developed and validated against experimental results. These filtration models allow system design and optimization, which is enabled by the tunable additive manufacturing approach used to fabricate the filters. Filtration efficiencies were also determined for solid particles, where the influence of the van der Waals and capillary adhesion forces on filtration efficiency were investigated. It was found that for dry filters, where van der Waals adhesion forces dominate, filtration efficiencies for filters were diminished beyond a threshold flowrate due to the dominance of the Saffman lift force acting on captured, wall-bound particles causing them to detach from the interior filter surfaces. For wetted filters, where capillary adhesion forces dominate, this diminishing efficiency was not observed. Lastly, multiplexed inertial coalescence filters were implemented in a liquid-gas chemical process for CO2 capture using a liquid amine spray as a means for accelerating liquid-gas chemical processes by enabling high-surface-area interaction between liquids and gasses. The liquid amine spray reactors were shown to be able to achieve large liquid surface-area-to-system-volume ratios, and correspondingly large volumetric CO2 mass transfer rates when compared to existing thin-film processes. These larger volumetric rates were shown to reduce system capital costs by 3-10x resulting from substantial overall system size reductions. Models for CO2 mass transfer rates were developed and showed good agreement with experimentally observed CO2 mass transfer rates.Item Teflon AF–Coated Nanotextured Aluminum Surfaces for Jumping Droplet Thermal Rectification(Wiley, 2024) Shimokusu, Trevor J.; Nathani, Alia; Liu, Zhen; Yap, Te Faye; Preston, Daniel J.; Wehmeyer, GeoffJumping droplet thermal diodes (JDTDs) are promising candidates to achieve thermal rectification for next-generation thermal control. However, most prior demonstrations of JDTDs have relied on monolayer-coated copper-based superhydrophobic (SHPB) surfaces, while lower-cost aluminum JDTDs with more durable thin polymeric coatings have not been explored. In this work, a JDTD is constructed that employs SHPB aluminum surfaces coated with protective thin films of Teflon AF (amorphous fluoropolymer) 1601. Measurements for different heating orientations, gap heights (H), and fill ratios (ϕ) show that a maximum thermal rectification ratio of 7 can be achieved for H = 2.4 mm and ϕ = 10%. A thermal circuit is demonstrated that uses the JDTD to rectify time-periodic temperature profiles, achieving thermal circuit effectiveness values up to 30% of the ideal-diode limit. Coupon-level durability tests and device-level cycling show that dip coated Teflon AF enables stable operation of Al JDTDs over >20 cycles, improving on the performance of a monolayer-coated surface that fails after 5 cycles. The findings of this work signify that Teflon AF coated Al SHPB surfaces can be used for thermal rectification and motivate future research into Al JDTDs for advanced thermal management applications.Item Thermally accelerated curing of platinum-catalyzed elastomers(Elsevier, 2024) Yap, Te Faye; Rajappan, Anoop; Bell, Marquise D.; Rasheed, Rawand M.; Decker, Colter J.; Preston, Daniel J.Silicone elastomers exhibit extraordinary compliance, positioning them as a material of choice for soft robots and devices. To accelerate curing times of platinum-catalyzed silicone elastomers, researchers have employed elevated temperatures; however, knowledge of the requisite duration for curing at a given temperature has remained limited to specific elastomers and has relied primarily on empirical trends. This work presents an analytical model based on an Arrhenius framework coupled with data from thermo-rheological experiments to provide guidelines for suitable curing conditions for commercially available addition-cured platinum-catalyzed silicone elastomers. The curing reaction exhibits self-similarity upon normalizing to a dimensionless reaction coordinate, allowing quantification of the extent of curing under arbitrary time-varying thermal conditions. Mechanical testing revealed no significant changes in properties or performance as a result of thermally accelerated curing. With this framework, higher throughput of elastomeric components can be achieved, and the design space for elastomer-based manufacturing can be developed beyond conventional casting.Item Embargo Understanding and Mitigating Airborne Contamination on Surfaces(2024-07-30) Liu, Zhen; Preston, Daniel J.Contamination from airborne hydrocarbons drastically affects surface chemistry by partially or completely passivating surfaces, in turn hindering nanomanufacturing, limiting characterization techniques, and generating controversies regarding fundamental studies of advanced materials. Consequently, inhibiting contamination is crucial for experiments and applications requiring clean surfaces. However, hydrocarbon contamination is often overlooked and hard to avoid in practice due to the ubiquitous nature of volatile organic compounds in the surrounding environment and the spontaneity of the contamination process; moreover, the evolution of surface contamination under typical storage methods (such as high vacuum) and within small structures or geometries is not well-understood. In the work presented in this thesis, we investigated how—counter to the belief that typical ultra-high vacuum (UHV) environments can reduce exposure to airborne contaminants— contamination occurs and is often even accelerated inside these UHV chambers. We experimentally and theoretically showed that samples with different initial levels of contamination approached the same equilibrium value, demonstrating that both hydrocarbon net adsorption and net desorption are able to occur within UHV. This study highlights a critical consideration for surface scientists, and provides routes to mitigate surface contamination effects. Furthermore, we developed a passive clean storage technology that employs an ultra-clean and high-surface-area medium that can be sacrificed as a getter for containments to maintain cleanliness of materials inside the storage device. The scalability, low cost, reusability, and environmentally friendly fabrication of this approach yield a promising method for storage and transportation of contamination-sensitive materials, which in turn benefits microfluidics and diagnostics, nanofabrication in computer chips, fundamental studies of advanced materials, and more. Finally, beyond inhibiting contamination to pursue clean storage techniques, we studied contamination-induced spatiotemporal variation of surface wettability in structures. We predicted the spatial and temporal distributions of contamination on surfaces in a detailed molecular diffusion–adsorption model and demonstrated the spatiotemporal evolution by characterizing surface wettability in high aspect ratio channels. The resulting understanding of the wettability variation within high aspect ratio surface structures offers guidelines for the design of spatially patterned wettability for tailored fluid manipulation and enhanced boiling and condensation heat transfer utilizing hydrocarbon diffusion and adsorption processes.