MIT scientists shrink glucose monitor to watch size using light waves

For people with diabetes, the daily routine is brutal: multiple finger pricks, constant sensor replacements, skin irritation that never quite goes away. MIT researchers think they've found a way out.

A team at the university's Laser Biomedical Research Center has developed a noninvasive glucose monitor that uses light waves instead of needles. The current prototype is about the size of a shoebox—not exactly wearable yet—but the scientists say a watch-sized version is within reach. The research, published in Analytical Chemistry, builds on 15 years of work exploring how light particles can read glucose levels directly through skin.

How light becomes a glucose detector

The technology relies on Raman spectroscopy, a technique that bounces near-infrared and visible light off skin cells and analyzes the signals that bounce back. The trick was filtering out noise from unrelated molecules. In 2020, researchers solved this by firing Raman signals at tissue from one angle while shining near-infrared light from another, essentially isolating just the glucose information in the signal.

The breakthrough that made miniaturization possible came from ruthless simplification. Instead of capturing the entire light spectrum—which contains roughly 1,000 bands of data—the team identified just three bands needed to measure glucose. "By refraining from acquiring the whole spectrum, which has a lot of redundant information, we go down to three bands," explained researcher Arianna Bresci. "With this new approach, we can change the components commonly used in Raman-based devices, and save space, time and cost."

Each measurement takes just over 30 seconds and matches the accuracy of commercial wearable monitors already on the market.

Why this matters beyond comfort

The pain of finger pricks isn't the only problem. Many people with diabetes simply don't test as often as they should because of the friction involved—multiple daily pricks add up. That under-testing leads to missed warning signs and serious complications. "Nobody wants to prick their finger every day, multiple times a day," said MIT research scientist Jeon Woong Kang. "Naturally, many diabetic patients are under-testing their blood glucose levels, which can cause serious complications."

A truly noninvasive option could change that equation. If monitoring becomes as simple and painless as checking a watch, more people might actually do it.

The team's next steps involve scaling the device down further and running larger clinical trials across different skin tones—a crucial detail often overlooked in medical device development. "If we can make a noninvasive glucose monitor with high accuracy, then almost everyone with diabetes will benefit from this new technology," Kang said.

The path from shoebox to wristband won't be instant, but the direction is clear.