Samantha A. McBride

Microplastics (MPs) are now ubiquitous across both built and natural environments. Their environmental fate and transport are governed by chemical and physical properties that evolve with weathering, making accurate characterization of these properties essential for predicting environmental behavior and informing mitigation and remediation strategies. Environmental weathering processes, particularly UV aging, can substantially alter plastic physicochemical properties over time and can also affect the fluorescence behavior of stained MPs, an important consideration given the widespread use of fluorescence microscopy for their detection and identification. Here, we investigated the physicochemical evolution of ten widely used polymers (PP, HDPE, LDPE, EPS, PS, PC, ABS, PVC, PET, and PA) subjected to artificial weathering under UVA (365 nm) irradiation and full-spectrum solar radiation for up to 333 and 150 days, respectively. Changes in surface roughness (RMS), water contact angle (WCA), chemical composition (Hydroxyl and Carbonyl groups) and fluorescence behavior were quantified to characterize degradation-induced transformations and evaluated using correlational analyses, including principal component analysis biplots and Spearman’s rank correlation coefficients. Our results show that physical and chemical degradation followed distinct temporal trajectories. RMS and WCA evolved in non-monotonic, sinusoidal-like patterns characterized by alternating roughening, smoothing, and surface reorganization, whereas chemical oxidation of hydroxyl and carbonyl groups progressed monotonically according to power-law kinetics. The fluorescence response of weathering induced red-shift of Nile Red-stained MPs closely tracked chemical oxidation, particularly carbonyl formation, rather than surface restructuring. Despite convergence in fluorescence color with progressive weathering, multispectral fluorescence imaging (FIMAP) maintained high classification accuracy. Notably, oxidation kinetics varied substantially among polymers and between UVA and full-spectrum exposures, highlighting the strong influence of polymer chemistry, exposure duration, and light source on degradation pathways. Together, these findings demonstrate that MPs weathering is highly polymer- and condition-specific and underscore the need for caution when using artificial aging approaches to represent environmentally relevant weathered plastics. Graphical Abstract

Multiphase displacement is important in oil recovery, microfluidics, and CO${}_{2}$ capture. We study viscous oil trapping in microfluidic devices with sinusoidal pockets during water invasion. Varying capillary number (Ca), viscosity ratios, and pore geometries reveals that higher oil viscosity and water velocities increase oil trapping due to transition from meniscus displacement to viscous fingering. We find that trapping dynamics at high Ca are geometry independent. Our three-dimensional model based on the long-wave approximation predicts some experimental observations, such as increased oil retention at higher Ca and viscosity ratios, and the characteristic interfacial shape of trapped oil.

Effective methods for cleaning surfaces are important for applications including dentistry, healthcare, micro-devices, and the manufacturing of electronic components and semiconductors. For example, surgical and dental instruments are susceptible to accumulation of aggregates and biofilm formation, which can lead to cross-contamination when ineffectively cleaned and reused. Complex fluids such as micro-fibrillated cellulose (MFC) can greatly assist in mechanically cleaning surfaces by removing strongly adhered aggregates without abrading the underlying material. We demonstrate that the heterogeneous structure of micro-fibrillated cellulose is effective in removing adhered particulates from surfaces and we characterize the cleaning efficiency of MFC suspensions in representative flow configurations. The experiments reported here involve flowing MFC solutions at various concentrations and at controlled shear rates through a rectangular microfluidic channel. Fluorescence microscopy is used to measure the removal of fluorescent particles that are adhered to the glass surface of the microfluidic device by electrostatic and surface forces. The particle removal with time is analyzed for each concentration of the MFC suspension and each shear rate to determine cleaning effectiveness. The rheology of the MFC solutions is also characterized and correlated to cleaning performance. We find that cleaning effectiveness increases with increasing fiber concentration and with increasing shear rate. Additionally, we compared the cleaning performance of the MFC suspensions with fluids that share similar rheological properties to highlight the role of shear thinning, elasticity, and tribology. Finally, we examine how sharp corners/edges within a microfluidic channel hinder cleaning and identify strategies for mitigating this hindrance.

Microplastics (MPs) are emerging contaminants in aquatic, terrestrial, and biological matrices whose degradation and bioaccumulation in food chains due to water and air pollution harm plants, animals, and humans alike. Common MP detection involves FTIR & Raman spectroscopy, or fluorescence microscopy. All these methods can be labor-intensive, especially since MP sizes often follow a power law with excessive smaller plastics. Thus, subsampling methods are often employed, which examine smaller regions of interest to enable extrapolating of data to save time. This project analyzes several geometric subsampling layouts for MPs captured on a filter, specifically using fluorescence imaging, for which there has been limited work comparing. Across these layouts, the most accurate layouts tended to be those with radial orientations, specifically wedges that may be able to capture the differences in MP concentration along the radius. With more samples and samples with higher MP counts, more precise conclusions can be made in comparing layouts.

Computer-assisted psychotherapy programs have demonstrated efficacy and potential for improving access to mental health services. However, little is known about their implementation, uptake and acceptability in real-world settings. As a quality improvement effort, we designed and implemented a computer-assisted cognitive-behavioral therapy (cCBT) program for adults in an outpatient specialty mental health clinic. We sought to increase access to psychotherapy services while maintaining good patient uptake and acceptability. The program included two pathways: (I) a cCBT-only pathway in which new clinic patients had access to online modules and up to ten 30-min telehealth appointments with a mental health clinician; and (II) an augmented-psychotherapy pathway in which clinicians recommended and incorporated online modules to patients already established in the clinic. The online content for the program was a vendor website that included 9 modules with written content, videos and interactive exercises to teach cognitive-behavioral skills. Twenty-seven patients started the program over 12 months (18 in the cCBT-only pathway and 9 in the augmented-psychotherapy pathway). Twelve patients (44.4%) completed all 9 modules of the program and 18 (66.7%) completed at least half the program. Engagement was higher in the cCBT-only pathway than in the augmented-psychotherapy pathway. Twelve of 18 cCBT-only patients responded to an acceptability survey with 83.3% indicating they were satisfied and 41.7% indicating the program met their needs. Clinician satisfaction was good among all three participating clinicians. The cCBT-only program provided timely access to psychotherapy services for new patients but uptake was very low with just 2.4% of new patients contacting the clinic for psychotherapy starting in the cCBT-only pathway. Many new callers elected to receive external referrals for more traditional forms of psychotherapy. Based on this low uptake, computer-assisted psychotherapies may fit best in settings where patients have not yet identified the specific type of care they wish to seek. Systems looking to adopt similar programs may also benefit from allowing ample time to develop industry partnerships, carefully considering the customizability and technical support available for online products, and introducing the programs to patients early in treatment.

Fluid instabilities can be harnessed for facile self-assembly of patterned structures on the nano- and microscale. Evaporative self-assembly from drops is one simple technique that enables a range of patterning behaviors due to the multitude of fluid instabilities that arise due to the simultaneous existence of temperature and solutal gradients. However, the method suffers from limited controllability over patterns that can arise and their morphology. Here, we demonstrate that a range of distinct crystalline patterns including hexagonal arrays, branches, and sawtooth structures emerge from evaporation of water drops containing calcium sulfate on hydrophilic and superhydrophilic substrates. Different pattern regimes emerge as a function of contact line dynamics and evaporation rates, which dictate which fluid instabilities are most likely to emerge. The underlying physical mechanisms behind instability for controlled self-assembly involve Marangoni flows and forced wetting/dewetting. We also demonstrate that these patterns composed of water-soluble inorganic crystals can serve as sustainable and easily removable masks for applications in microscale fabrication.

A newly discovered mechanism by which salt crystals leap off nanoengineered surfaces may lead to the development of industrial materials that resist the buildup of minerals from fresh and salt water.

Objective: To examine burnout and perspectives on videoconferencing over time for the mental health workforce. Methods: Members of an academic psychiatry department completed two anonymous surveys about virtual work and burnout 18 months apart (T1 n = 274, response rate = 66.8%; T2 n = 227, response rate = 36.7%). A subset completed the burnout subscale of the Stanford Professional Fulfillment Index (T1 n = 145; T2 n = 127). Results: Respondents were well satisfied with videoconferencing at both time points and satisfaction was higher at T2. Videoconferencing was not perceived to contribute to feelings of fatigue at either time point and burnout levels decreased from T1 to T2. Conclusions: Videoconferencing is well received by the mental health workforce and is not widely perceived to contribute to feelings of fatigue. Longer use of videoconferencing coincided with decreased levels of burnout. There are likely benefits to virtual work for the mental health workforce and virtual work may be protective from burnout.

International audience

High Resolution Image Download MS PowerPoint Slide Anthropogenic greenhouse gas emissions from power plants can be limited using postcombustion carbon dioxide capture by amine-based solvents. However, sustainable strategies for the simultaneous utilization and storage of carbon dioxide are limited. In this study, membrane distillation–crystallization is used to facilitate the controllable production of carbonate minerals directly from carbon dioxide-loaded amine solutions and waste materials such as fly ash residues and waste brines from desalination. To identify the most suitable conditions for carbon mineralization, we vary the membrane type, operating conditions, and system configuration. Feed solutions with 30 wt % monoethanolamine are loaded with 5–15% CO 2 and heated to 40–50 °C before being dosed with 0.18 M Ca 2+ and Mg 2+ . Membranes with lower surface energy and greater roughness are found to more rapidly promote mineralization due to up to 20% greater vapor flux. Lower operating temperature improves membrane wetting tolerance by 96.2% but simultaneously reduces crystal growth rate by 48.3%. Sweeping gas membrane distillation demonstrates a 71.6% reduction in the mineralization rate and a marginal improvement (37.5%) on membrane wetting tolerance. Mineral identity and growth characteristics are presented, and the analysis is extended to explore the potential improvements for carbon mineralization as well as the feasibility of future implementation.

The undesirable, yet inevitable, presence of bacterial biofilms in spacecraft poses a risk to the proper functioning of systems and to astronauts' health. To mitigate the risks that arise from them, it is important to understand biofilms' behavior in microgravity. As part of the Space Biofilms project, biofilms of Pseudomonas aeruginosa were grown in spaceflight over material surfaces. Stainless Steel 316 (SS316) and passivated SS316 were tested for their relevance as spaceflight hardware components, while a lubricant impregnated surface (LIS) was tested as potential biofilm control strategy. The morphology and gene expression of biofilms were characterized. Biofilms in microgravity are less robust than on Earth. LIS strongly inhibits biofilm formation compared to SS. Furthermore, this effect is even greater in spaceflight than on Earth, making LIS a promising option for spacecraft use. Transcriptomic profiles for the different conditions are presented, and potential mechanisms of biofilm reduction on LIS are discussed.

Scaling or mineral fouling occurs due to the presence of dissolved minerals in water. Scaling is problematic in numerous industrial and household plumbing applications where water is used. The current methods of scale removal often utilize harsh chemicals that are not environmentally friendly. The evaporation of a saline droplet provides a platform to study the role of the substrate in the dynamics of crystallization during scaling. In the present work, we show out-of-plane growth of crystal deposits during the evaporation of saline droplets of aqueous potassium chloride on a heated smooth and microtextured hydrophobic substrate. These out-of-plane deposits, termed as "crystal legs", are in minimal contact with the substrate and can be easily removed from the substrate. The out-of-plane evaporative crystallization of saline droplets of different initial volumes and concentrations is observed irrespective of the chemistry of the hydrophobic coating and the crystal habits investigated. We attribute this general behavior of crystal legs to the growth and stacking of smaller crystals (size ∼10 μm) between the primary crystals toward the end of evaporation. We show that the rate at which the crystal legs grow increases with an increase in the substrate temperature. A mass conservation model is applied to predict the leg growth rate, which agrees well with the experiments.

A recently discovered phenomenon in which crystalline structures grown from evaporating drops of saline water self-eject from superhydrophobic materials has introduced new possibilities for the design of anti-fouling materials and sustainable processes. Some of these possibilities include evaporative heat exchange systems using drops of saline water and new strategies for handling/processing waste brines. However, the practical limits of this effect using realistic, non-ideal source waters have yet to be explored. Here, we explore how the presence of various model aquatic contaminants (colloids, surfactants, and calcium salt) influences the self-ejection phenomena. Counterintuitively, we find that the addition of "contaminant" chemistries can enable ejection under conditions where ejection was not observed for waters containing only sodium chloride salt (e.g., from smooth hydrophobic surfaces), and that increased concentrations of both surfactants and colloids lead to longer ejection lengths. This result can be attributed to decreased crystallization nucleation time caused by the presence of other species in water.