Image created by Dr. Michael J. Miller
Purdue University researchers have developed a device for more conveniently detecting pathogens in health care settings, on farms and in food production operations.
Nafisa Rafiq, a Ph.D. student in biomedical engineering, and Mohit Verma, associate professor of agricultural and biological engineering, described their new system in the IEEE Sensors Journal. Rafiq, Verma and Bibek Raut, also a Ph.D. student in biomedical engineering at Purdue, have submitted a patent application for related technologies. Verma serves as chief technology officer of Krishi, a startup company that develops molecular assays.
"The device marks an advancement in the suite of tools that are available to conduct molecular assays in the field," Verma said. "Due to its versatility and ease of use, it has the potential to be applied across multiple fields."
Development and features of IsoHeat device
Rafiq was among Verma's co-authors of a 2024 paper that announced the development of a new biosensor for fast and easy detection of fecal contamination on produce farms. The new publication announces the development of a system called IsoHeat for processing those test samples.
"This project was mainly about hardware, fabricating the water bath system to process our biological samples," Rafiq said. She and Verma designed the device for performing an assay called loop-mediated isothermal amplification (LAMP). Invented 25 years ago, LAMP detects microbes by amplifying—making extra copies of—target nucleic acids. LAMP's chemical reaction happens at a single, constant temperature to detect any pathogen or nucleic acid targets, such as antimicrobial resistance.
"We aimed to make the system portable, having uniform heat distribution throughout the water while heating and allowing the user to observe continuous changes with the naked eye," Rafiq and Verma reported. "The ease of use, precise temperature control in a sealed setup, and visual monitoring of LAMP assays make our device novel and ideal for rapid on-farm molecular diagnostics."
Testing, design and user considerations
Rafiq and Verma tested their IsoHeat device against a widely used piece of equipment for heating LAMP assays in the field. IsoHeat reached the target temperature of 149 degrees Fahrenheit (65 degrees Celsius) in about 12 minutes. The commercially available precision cooker they tested IsoHeat against needs about 36 minutes to reach the same temperature.
Further, as Rafiq and Verma noted in their paper, "IsoHeat was specifically designed to be operated by nonspecialists in the field or low-resource settings."
Drawing on her undergraduate training in industrial engineering, Rafiq fabricated various parts of the tabletop device using 3D printing and laser-cutting technologies. The finished product consists mainly of an electrical system that heats and maintains water at the desired temperature, the hardware and a power supply unit.
"The initial challenge that I faced was to select the optimized material to fabricate," Rafiq said. "We needed to think about cost-effectiveness. Also, we needed to think about portability. It must be light and easy to manage for the end user to transport." Further, because the system is electrical and involves water, "we had to make sure, above everything, that the system is completely safe and user-friendly."
Convenience and practical applications
Convenience features include a sealed container to help maintain uniform heating, a hanging sample holder and simple touchscreen controls. The device dispenses with the need to tape samples to the container wall in hot water while wearing protective gloves.
"We can prepare biological samples and then use our system to process those samples and get our output anywhere," Rafiq said.
Reference
Nafisa Rafiq et al, Design and Development of a Field-Deployable Water Bath for Loop-Mediated Isothermal Amplification Assay, IEEE Sensors Journal (2025). DOI: 10.1109/jsen.2025.3588790
Abstract
Nucleic acid testing has become a prominent method for rapid microbial detection. Unlike polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP) is a simple method of nucleic acid amplification where the reaction can be performed at a constant temperature and the output provided in a colorimetric format. A transparent water bath is a desirable instrument to perform the heating and observe the visual results. However, existing methods of heating water are not convenient for loading and unloading the test samples. Here, we developed a field-deployable water bath—an isothermal heater called IsoHeat for short—which is dedicated to performing LAMP reactions. Using 3D-printing and laser-cutting technology, we fabricated different parts and mechanically assembled the parts to develop the device. Users can commence the heating by pressing the start button on the screen after entering the target temperature. Subsequently, the device heats the water and maintains the target temperature through a PID algorithm-based control system. We demonstrate that IsoHeat can operate in environmental temperatures ranging from 5 ∘ C to 33 ∘ C, and it can conduct LAMP reactions in liquid format as well as in paper-based devices. IsoHeat is more efficient and user-friendly compared to a commercially available immersion-heating device, which is often used to perform LAMP reactions. This newly developed device would be helpful to detect pathogens conveniently in the field (e.g., at point-of-care for human applications, on farms for plant and animal applications, and in production facilities for food safety applications).