Published Aug 26, 2025 | 8:00 AM ⚊ Updated Aug 26, 2025 | 8:00 AM
Representative image. Credit: iStock
Synopsis: By offering affordability, speed, ease of use, and reliability, ε-µD meets key WHO criteria and takes a major step toward making antimicrobial susceptibility testing (AST) more accessible, especially in low-resource settings. Translating this into clinical benefit is central to the team’s plans.
Doctors could get antibiotic susceptibility results in about three hours, thanks to a low-cost, chip-based device developed by researchers at the Indian Institute of Technology Madras (IIT Madras).
The innovation offers a faster alternative to conventional tests that typically take two to three days. Using electrochemical signals, the device can determine whether bacteria are resistant or susceptible to a given antibiotic.
Built as a lab-on-chip and known as ‘ε-µD’, it is based on screen-printed carbon electrodes embedded in a simple microfluidic chip. By avoiding costly metals, complex fabrication steps and the need for highly skilled technicians, the approach keeps costs down and makes the device suitable for smaller clinics and rural healthcare centres.
Designed for speed, sensitivity and ease of use, ε-µD holds strong potential for early diagnosis and better treatment of bacterial infections, particularly in regions with limited access to advanced laboratory infrastructure.
Antimicrobial resistance (AMR) is among the most pressing challenges for health systems worldwide. The World Health Organization (WHO) has identified AMR as one of the top ten threats to global health, with estimates suggesting that nearly 4.95 million deaths worldwide in 2019 were associated with bacterial AMR.
The burden is especially high in low and middle-income countries, where diagnostic facilities are limited and infections often go untreated or are improperly managed. In such settings, faster, easier testing can directly influence patient outcomes by helping doctors prescribe targeted antibiotics and avoid misuse, a major cause of resistance.
To address the drawbacks of modern techniques that use costly metals, complex fabrication, or skilled technicians, the IIT Madras team built ε-µD with screen-printed carbon electrodes in a simple microfluidic chip, keeping the device economical and practical for wider use.
The device uses Electrochemical Impedance Spectroscopy to monitor changes in electrical properties as bacteria interact with antibiotics.
As Prof S Pushpavanam, YBG Varma Institute Chair Professor, Department of Chemical Engineering, IIT Madras, explained: “An important aspect of our device is the use of a specially prepared nutrient solution that serves a dual purpose. It not only supports bacterial growth, which is essential for testing, but also enhances the sensitivity of the electrical signals we use for detection. As the bacteria grow, they cause measurable changes in the electrical properties of the solution, which our system can accurately track.”
Dr Richa Karmakar, Assistant Professor in the Department of Biotechnology, IIT Madras, noted, “The device monitors how the electrical signal changes over time to determine whether bacteria are continuing to grow in the presence of an antibiotic.”
She explained that if bacteria are resistant, they continue multiplying despite the drug, producing distinct changes in the electrical signal. By contrast, when bacteria are killed, their growth is suppressed and the signal remains largely unchanged.
To make this distinction clearer, the researchers developed a metric called the Normalized Impedance Signal (NIS), which reliably separates resistant from non-resistant strains within hours.
For validation, the researchers tested gram-negative E. coli and gram-positive B. subtilis with ampicillin (kills bacteria) and tetracycline (blocks growth). The device identified resistance within three hours. They also tested urine samples spiked with E. coli and successfully detected tetracycline resistance, showing its clinical potential.
By offering affordability, speed, ease of use, and reliability, ε-µD meets key WHO criteria and takes a major step toward making antimicrobial susceptibility testing (AST) more accessible, especially in low-resource settings. Translating this into clinical benefit is central to the team’s plans.
Prof S Pushpavanam explained the potential impact, “This approach will make a real impact on patients in ICUs, who may be suffering from complications due to bacterial infections. This will help doctors prescribe the right treatment and can be life saving.”
He also detailed the ongoing work and future plans. “Currently, we are doing clinical validation in collaboration with the IITM Institute Hospital. After rigorous clinical validation, we plan to commercialise this through our startup, Kaappon Analytics India Private Limited,” he said.
The research has been published in Nature Scientific Reports, a peer-reviewed, open-access journal from Nature Portfolio covering all areas of natural sciences.
(Edited by Amit Vasudev)
