The design and usage of a portable incubator for inexpensive in-field water analysis

  • Brian T. Heligman Department of Material Science, University of Texas, USA

  • Alice Zhao
  • Evan Bartilson PLH Advanced Engineering

  • Abhay Gupta Department of Material Science, University of Texas, USA
  • Joshua Hannan Modular, Inc.
  • Maimouna Diop Mechanical Engineering Graduate, University of Texas
  • Robert L. Read Public Invention
Keywords: Bacterial analysis, off-grid functionality, Petrifilm, water quality, portable instrumentation, E. coli


Humanitarian engineers need an inexpensive, fast, visually compelling way to assess bacterial water quality in remote locations. One way to do this is with 3M Petrifilm E. coli/Coliform (EC) Count Plates to detect E. coli in water samples. These require incubation at close to body temperature. To meet this need, we provide a free, open-source design of a battery-powered incubator capable of maintaining 35°C ± 1°C for up to 65 hours in ambient temperature of 25°C. Our incubator, called the Armadillo, can be replicated by an ordinarily skilled person in five hours for under USD $200.00 in materials cost. This paper summarises the reference documentation for construction, sample handling, inoculation, and incubation using Petrifilms and the Armadillo. Colony-forming unit (CFU) counts generated by the Armadillo are compared side-by-side with a laboratory-grade incubator. Incubation performance at ambient temperatures of 25°C and 4°C shows that a single battery charge reliably powers a full incubation period of 48 hours under normal ambient temperatures.

Author Biography

Robert L. Read, Public Invention

Founder, Public Invention

PhD, Computer Science

Presidential Innovation Fellow


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