ENTIRELY-3D PRINTED MICROFLUIDIC PLATFORM FOR ON-SITE DETECTION OF DRINKING WATERBORNE PATHOGENS Eric C. Sweet, Nathaniel Liu, Juhong Chen and Liwei Lin Berkeley Sensors and Actuators Center, University of California, Berkeley, USA MEMS 2019, Seoul, KOREA, 27 - 31 January, 2019 ABSTRACT This work presents a novel handheld, manually- actuated microfluidic prototype designed for on-site colorimetric detection of infectious pathogens in drinking water. We have also developed a custom drop-casting protocol we use to pre-load the entirely 3D printed device, fabricated via ultra-high resolution additive manufacturing technology, with colorimetric enzymatic reagents and bacteria-specific nutrients, which we use to experimentally detect Escherichia coli (E. coli) bacteria in model drinking water, as well as to determine a limit of detection of 1e6 cfu/mL of E. coli in 6 hours. Our proposed microfluidic platform will enable entirely on-site water quality testing, eliminating the need for off-site, lab-based water sample analysis, thus significantly increasing analytical throughput. Furthermore, we have developed a design methodology for engineers to customize the number of desired on-chip pathogen detection chambers, enabling multiplexed detection of multiple pathogens. INTRODUCTION Bacterial contamination of potable freshwater sources, such as wells, springs, streams and reservoirs, results in the highest annual number of hospitalizations and fatalities in the United States, and is the leading cause of worldwide infectious disease outbreaks [1]. Water contaminated by pathogenic enteric bacteria such as E. coli, Shigella and Salmonella, usually the result of poor sanitation and fecal pollution, kills roughly 1.6 million children under the age of five worldwide, more than 80% of whom from rural communities in the developing world [2]. Thus, various groups such as the World Health Organization and local municipal water suppliers frequently assess the safety of drinking water sources worldwide by testing water samples for the presence of harmful bacteria. Conventional methods of water quality testing, however, are typically time-consuming, costly and labor-intensive processes, involving collection of a water sample at a given location and shipment to an off-site facility, followed by enrichment and pathogen detection using expensive equipment operated by highly-skilled personnel (Figure 1a) [3], which can take upwards of 24 to 48+ hours to deliver definitive analytical results [4]. An ever-increasing need therefore exists for developing technologies which will enable entirely on-site water sample analysis by eliminating time-consuming sample transportation and laboratory-based sample processing [5]. Various microfluidic-based approaches have been developed that advertise high-throughput analysis of micro-scale sample fluid volumes [6]; however, many such systems, for example smartphone-based fluorescent-optofluidic devices [7] and paper-based bacterial immunoassay microfluidic chips [1], still require the use of bulky, powered equipment to facilitate fluid actuation, sample processing and biological detection [8], thus are still restricted to use in high-resource facilities [3]. Figure 1: Motivation and concept of our proposed on-site bacteria detection device. (a) Turnaround time for conventional water sample analysis techniques of 1-2+ days limits throughput of pathogen detection. (b) Proposed hand-held device enables multiplexed, on-site sample collection, handing, enrichment & detection of (c) “n” number of target pathogens using “n” chambers pre-loaded with enzyme-specific reagents & nutrients, resulting in rapid multiplexed pathogen detection & treatment recommendations for an affected population, on-site. Pathogen detection 24-48+ hours Sample shipment Laboratory enrichment Communication of results On-site collection vectorstock.com/ n chambers (colorimetric reagent + nutrients) Detection of n bacteria species! Pre-Loaded Reagent Chambers on Device Bacteria A Bacteria B Bacteria n Control … … … … … … … … www.indiamart.com On-site collection, enrichment & detection Bacteria B Contaminated water source ~6 hours Bacteria A a b Proposed System www.indiamart.com c Bacteria in Sample A B A + B + n n