Low-cost, field-deployable, near-time methods for assessing water quality are not available when and where waterborne infection risks are greatest. We describe the development and testing of a novel device for the measurement of tryptophan-like fluorescence (TLF), making use of recent advances in deep-ultraviolet light emitting diodes (UV-LEDs) and sensitive semiconductor photodiodes and photomultipliers. TLF is an emerging indicator of water quality that is associated with members of the coliform group of bacteria and therefore potential fecal contamination. Following the demonstration of close correlation between TLF and E. coli in model waters and proof of principle with sensitivity of 4 CFU/mL for E. coli, we further developed a two-LED flow-through configuration capable of detecting TLF levels corresponding to “high risk” fecal contamination levels (>10 CFU/100 mL). Findings to date suggest that this device represents a scalable solution for remote monitoring of drinking water supplies to identify high-risk drinking water in near-time. Such information can be immediately actionable to reduce risks.

In Sub-Saharan Africa, around 80% of residential energy demand is for cooking, with over 760 million people without access to clean cooking fuels and stoves. Particulate matter smaller than 2.5 microns (PM${}_{2.5}$) is a significant pollutant from biomass burning and is linked to respiratory and cardiovascular diseases, as well as adverse pregnancy outcomes. Energy poverty further reinforces gender disparities, keeps children from schools, causes environmental degradation, and interferes with social and economic development. Lack of access to and inadequate adoption of clean cooking stoves and fuels are key barriers to improved air quality. This paper presents a field experiment nested within a large-scale health efficacy trial. The aim of the experiment was to evaluate the effects of access to air quality data and dynamic feedback on indoor air pollution (IAP) and personal exposure. Ninety households in Rwanda were enrolled and provided with an air quality sensor and feedback device, which measured real-time indoor air quality as PM${}_{2.5}$ for sixteen weeks. After six weeks, PM${}_{2.5}$ levels were provided dynamically to households through a display and an auditory alarm. We examined the effects of receiving this feedback on IAP and personal exposure. While access to air quality data did not, in aggregate, improve PM${}_{2.5}$ levels, we did observe several promising correlations worthy of further investigation. The associations between personal exposure or rainfall and increased PM${}_{2.5}$ were reduced after households had access to air quality data. We hypothesized that the behavior changes required to observe these effects—opening doors and windows and moving away from cooking sources—are easy and immediate, in contrast to the costs and complex logistics of entirely eliminating biomass cooking. The types of behavior changes that would directly impact household air pollution and exposure require more than just awareness and willingness to act.

Several approaches have been proposed in the literature supporting product design applied in low-income settings. These approaches have typically focused on individual- and household-level beneficiaries, with an emphasis on participatory, human-centered co-design methods. In this paper, we present a design approach that is, in contrast, focused on supporting providers of improved water, sanitation, and energy services. We establish requirements for design in these contexts, especially addressing design iteration. We describe sets of feedback systems between designers and various sources of expert knowledge, codifying roles of design stakeholders in this context. We demonstrate these principles across three case studies: a sanitation service monitoring technology in Kenya; a water flowmeter technology in Kenya; and a water storage monitoring technology in Sierra Leone.

Monitoring of microbiological processes in soil is important for understanding and improving soil health and agricultural productivity. Despite its significance, microbiological measurements are currently difficult to make in-situ and in real time. Evaluation of microbially-mediated soil processes usually involves manual sampling followed by laboratory analysis, which can be costly, time consuming, physically intensive, non-continuous, and reduces capacity for measuring changes at high temporal and spatial resolution, thereby limiting the ability to make prompt informed land management decisions. Low-cost soil sensors manufactured using printing techniques offer a potential scalable solution to these issues, allowing for wide distribution of sensors that collect time-series data for decomposition rates. Here, we tested the use of novel sensors for the evaluation of soil microbial processes. This comprises the first large-scale field deployment of these sensors, which use a biodegradable composite conductor that transduces microbial decomposition of substrates to a change in electrical resistance. Sensors were installed for 50 days across 44 experimental plots of a long-term grassland biodiversity restoration experiment, including treatments with additions of synthetic fertilizer, manure, mixed seed, and red clover, causing significant differences in soil microbial activity. Soil biological properties commonly used as soil health indicators, including microbial biomass and enzymatic activities related to carbon, nitrogen and phosphorus cycling, were measured using standard laboratory methods. Sensor responses were compared to these conventional soil health measures to better understand their potential utility by considering the signals of sensors within a set decomposition window and individual sensor degradation rates across various timescales, and correlating changes in signal variability with soil measured properties. All statistical approaches found positive correlations between the sensor signal and laboratory measurements of microbial biomass carbon and soil organic carbon, and some approaches found correlations with enzymatic measurements. These findings demonstrate the potential for the proxy measurement of soil microbial processes in-situ using readily distributable printed decomposition sensors, thereby supporting their potential for low-cost, high-resolution temporal and spatial monitoring of complex soil biological parameters and their ability to provide new insights into soil health.