Purdue University researchers have built a 3D printed, open-source alternative to the specialized groundwater-flow sensors that the U.S. Geological Survey (USGS) owns in only small numbers, and they can assemble each unit for a few hundred dollars, a fraction of the cost of the commercial hardware it replaces. The patent-pending device is designed to drop into monitoring wells and run for months to years at a stretch, reporting how water moves beneath the surface.
The work is led by Jacob Hosen, an assistant professor of internet-of-things and ecological analytics in Purdue’s Department of Forestry and Natural Resources, in collaboration with the open-hardware nonprofit River Restoration Intelligence and Verification (RRIV). Funding comes from the USGS Next Generation Water Observing System, the agency’s research arm for cheaper, faster water data.
A sensor you can print, then bake
Rather than relying on a single costly probe, the device infers groundwater movement from heat. Circuit boards carry arrays of temperature sensors that resolve both the speed and the direction of water moving through soil. The electronics live inside a 3D printed case that the team designs, prints, and iterates on directly in the lab a loop that lets them revise the hardware in hours rather than waiting on an outside manufacturer.
The housing turns out to be the difficult part, because a case that disturbs the flow corrupts the measurement. “A big part of designing an accurate sensor is creating a housing that won’t disrupt the water flow,” Hosen said. “We’re 3D printing textures that will recreate the soil environment, so the water flows through the sensor in the same way it flows through the ground.”
Manufacturing is kept deliberately small in scale. The team orders a handful of components from the U.S.-based vendors and does everything else in-house with a 3D printer and a specially modified toaster oven used to reflow the electronics. “We can make all of this with just a few vendors in the U.S., and then do the rest of the assembly in-house for just a few hundred dollars a unit,” Hosen said. “That’s not something you can do in most ecology labs.”
Building the devices in-house doubles as a teaching tool. Graduate and undergraduate students on the project pick up circuit-board assembly, 3D printing, and prototype iteration, skills usually confined to engineering labs rather than a forestry and natural-resources department.
Eight months underwater
Early durability testing has been the strongest signal so far: the sensors ran continuously underwater for seven to eight months without a failure. If that holds up at scale, the devices could become standard long-term fixtures in USGS wells, built for months-to-years of uninterrupted operation rather than short field campaigns.
Getting the data out is handled two ways at once. The sensors transmit wirelessly over LoRa networks, built out on campus by Purdue’s Agriculture IT group, while also writing to local storage as a backup, so readings survive even where connectivity is patchy in remote areas. Purdue’s expanding LoRa coverage is being used to test the telemetry on campus before deployment.
The first major field test is slated for a USGS site on the Kankakee River near the Illinois border, with additional units going into Purdue’s ACRE Wetland to study hydrology. Hosen developed the concept with Zaven Arra, lead engineer at RRIV; Keith Cherkauer, a professor of agricultural and biological engineering and director of the Indiana Water Resources Research Center, served as co-principal investigator.
The potential uses stretch well past academic hydrology. Hosen points to tracking contaminated groundwater plumes for the Department of Defense, monitoring how much water data centers pull from the ground, and assessing building stability in waterlogged soils. “It works anywhere that water moves underground,” he said.
Open hardware in a closed market
The telling choice is what Purdue is doing with the patent. It filed through the Purdue Innovates Office of Technology Commercialization not to sell licenses but to lock the design open, in line with RRIV’s premise: an open-source platform for water monitoring dense enough to track change over time. The gap is structural, when the reference instrument costs enough that even the USGS owns only a few, monitoring stays sparse.
The tactic has fresh precedent. In January 2025, Strathclyde researchers released a £50 open-source 3D printed microscope meant to democratize lab-grade microscopy for schools, clinics, and labs. Months later, a University of Edinburgh team open-sourced the Flex Printer, a sub-£400 machine that turns out working soft robots, explicitly to widen access to a field long gated by cost and expertise.
Open hardware has spent a decade democratizing the lab bench. Purdue’s bet is that the same logic survives eight months at the bottom of a well.
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Featured image shows Sensor being held by Jacob Hosen. Photo via Purdue University.
