Optical imaging is commonly used to investigate biological flows and cardiovascular disease using compliant silicone polydimethysiloxane (PDMS) Sylgard 184 geometries. However, selecting the working fluid with blood density and viscosity, and PDMS index of refraction (RI) for such experiments is challenging. Currently, water-glycerol is commonly used and sodium iodide (NaI) often added to increase the index of refraction without changing fluid viscosity. But the resulting fluid density is well above blood. Moreover, NaI is expensive, has safety and material discoloration concerns, and has been reported to affect non-Newtonian fluid behavior. Here, we present a new blood analog alternative based on urea. Urea is approximately five to fifteen times less expensive than NaI, safe and easy to handle, optically clear, and causes no discoloration. Water-glycerol-urea solutions, unlike those with NaI, simultaneously matched the density and viscosity of blood and RI of PDMS. Water-xylitol and water-xylitol-urea solutions are also possible blood analog solutions. Xanthan gum (XG)-water-glycerol non-Newtonian solutions maintained similar viscoelastic properties throughout the range of weight percent (about 15-25%) of urea and NaI used here. The results showed that the XG weight percent affected viscoelastic properties more than the weight percent of urea or NaI tested in this study. Overall, we demonstrate urea is useful for PDMS blood analog experiments and should also be considered as an inexpensive additive, and an alternative to NaI.

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Access to safe, sufficient water for health and sanitation is a human right, and the reliable disinfection of water plays a critical role in addressing this need. The environmental impact and sustainability of water disinfection methods will also play a role in overall public health. This study presents an investigation of the environmental life cycle impacts of four ultraviolet disinfection systems utilizing ambient solar radiation directly and indirectly for water disinfection in comparison to chlorination and water delivery for application in low-income settings. Product inspection and existing literature were used to define a life cycle functional unit of 1 m 3 of water for each system, which allowed quantification of material use, infrastructure requirements, and life cycle of the original components of each system and those needed to keep them operational for the studied lifespans (1, 5, 10, and 20 years) and scales (30, 100, 500, and 1000 L per day). For all studied cases, chlorine had the lowest impact in all impact categories, but end-user acceptance of chlorine in some settings is low, driving interest in low-impact alternatives. Disinfection based on low-pressure mercury lamps had the next lowest normalized impact in most categories and may represent a viable alternative, particularly for long-term (10+ years), high production (500+ liters per day) scenarios.

In 2010, the United Nations established access to safe drinking water as a basic human right; however, many areas around the globe still lack access. The interdisciplinary service-learning course "Water Supply in Developing Countries" was established at Purdue in 2012 to address the complex issue of water insecurity around the world. Over the past fi ve years, the course has produced teams involving students from nursing, engineering, agricultural economics, biology, and food science working together to develop sustainable, community-scale drinking water treatment systems. In partnership with Aqua Clara International, the student team in 2017 established a drinking water treatment system at the Ana Julia Diaz Luna primary school in the rural community of Las Cañas, Dominican Republic. In addition to the focus on a physical water system, they also collaborated with local educators to design a water, sanitation, and hygiene (WASH) education program. Students guided development of sustainable economic strategies to utilize the system for generation of revenue to reinvest in maintenance and improvements. The observations and lessons learned from the completed stages of this project have been applied to improve the effectiveness and effi ciency of subsequent interventions.