Advanced Biophotonic devices - what's available right now

It's that beautiful time of the year: Christmas carols, get togethers with family and friends, feasts that make you regret life decisions and the lights! Beautiful Yule decorations that make the gloomy darkness of late December oh so much more bearable! This got me thinking... Biophotonics, the science of light interaction with living objects, has been the hottest topic within the domain of Biomedical Engineering for a while now. But what has it delivered beyond the well known PPG and SpO2? Well, turns out it has, and some of those devices you can buy even right now!

Some of the pretty lights I am talking about

AGE sensor on a smartphone

The first—and arguably the most accessible—advanced photonic measurement you can find in a retail device is on Samsung’s Galaxy Watch 7 and Galaxy Watch Ultra, which offer the ability to measure Advanced Glycation End Products (AGEs) in the skin. These watches also have a wealth of other functions, but those go beyond the scope of this article. Advanced glycation end products (AGEs) are a family of compounds of diverse chemical nature that are the products of nonenzymatic reactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs are biomolecules that accumulate in the body over time, often associated with aging and chronic diseases. While these molecules are a deep topic in and of themselves, higher levels of AGEs have been shown to correlate with an elevated risk of cardiovascular events and other chronic conditions. There are many publications on the topic but a good summary can be found here: Meerwaldt et al. So how these devices do it? We know from literature that the detection of AGEs is based on the fluorescnce: when illuminated by a certain wavelenght (350–370 nm range for AGEs), the molecules will emit a light on a different wavelength (420–600 nm). This makes estimating the concentration of AGEs possible. The Galaxy watch reuires you wear it to bed and may not produce the desired result over just one night. This tell me that the algorith requires a significant ammount of data to be collected. Samsung licensed its sensor technology from Diagnoptics—a company whose benchtop AGE detectors can deliver readings in just 12 seconds. It’s not entirely clear why the watch takes significantly longer, especially since both measure roughly the same area of skin. One likely explanation is the watch’s power constraints. A wearable device has a much smaller energy budget than a dedicated analyzer, and UV or near-UV LEDs can be power-intensive. Consequently, the watch may need more time (or multiple measurements) to gather sufficient data for a reliable estimate.

Cuffless, noninvasive blood pressure monitor on your wrist

The next device is very impressive. The Aktiia continuous blood pressure monitor. The hardware of the device appears to be relatively simple: a wrist worn PPG device. But the algorithm behind the measurements has apparently been validated to be clinical-grade in various body positions, has comparable accuracy to widely accepted cuff-based devices and complies with relevant industry standard: ISO 81060-2.

The company does not share all that much specifics on the algorithm, but it appears to be tracking the tissue volumes at each heart stroke and having some sort of routine to correlate changes in the optical signal with the changes in blood pressure. Similar concepts were proposed in papers, but they seem to be the first to meet a stringent standard of evidence. The provide links to studies on theor website: Aktiia evidence. All told, an impressive device, particularly since it allows continuous monitoring that is simply not possible with cuff-based systems, and wildly impractical with invasive methods.

Glucose monitoring: no needles needed

The next device I want to present for you is the Liom (formerly Spiden) wearable Glucose monitor. Traditionally Glucose monitoring can be done in two ways. The invasive option relies on probes that break the skin and, through an electrochemical sensing process, look for glucose and metabolites in the interstitial fluid. Dexcom, Medtronic and other large companies tend to dominate this market. The second one is bioimpedance based non-invasive approach that is great but has one improtant caveat: it deos not work. Now, there is a third one and it's very impressive: a combination of photonics and machine learning allows accurate glucose sensing right on your wrist and with not a needle in sight! This company, much like the other two, does not divulge details on their device. It is known that Glucose can be picked up by an optical spectroscopy in a Near Infra Red (NIR) range. Likely, this is the basis of their device. It's also clear that the algorithm is not a straightforward one. That I can piece together from Liom looking for Senior Machine Learning specialists on a regular basis. If their LinkedIn is to be believed anyway. Liomn conducted a small pilot study yielding “promising” preliminary data on their non-invasive continuous glucose monitor (NICGM). Detailed results from this study are not yet publicly available. The pre-print is avaliable at MedRxiv. There is a registered Clinical Trial (NCT06272136): Liom has formally registered the “Spiden Non-Invasive Continuous Glucose Monitor Clinical Demo (NICGM) Trial,” signaling a more rigorous evaluation phase. Details on study design, endpoints, and results have not yet been released. Of all the devices mentioned, this is perhaps the most impressive and lifechanging one.

Rockley Photonics: The “Almost There” Contender

Rockley Photonics made headlines with its plan to integrate a suite of silicon photonic sensors—capable of monitoring blood pressure, temperature, hydration, and even glucose—onto a single chip. The concept involves shining multiple wavelengths of light through the skin and analyzing reflected signals, similar to the other devices but on a broader scale. Despite significant buzz and high-profile partnerships, Rockley has not yet delivered a commercially viable product. Early demonstrations claimed multi-parameter measurements, but the lack of a finalized consumer device has led to skepticism. Publicly released data are sparse, and what little exists comes primarily from company announcements rather than independent clinical trials. At this point, Rockley’s technology is not available in a consumer-facing device. While multiple press releases hinted at potential integrations with major wearables brands, nothing concrete has emerged. Whether Rockley’s platform will eventually reach consumers remains uncertain.

Conclusions

It's impressive to see that there are real, tangible benefits form all the research done on the topic of Biophotonics. The future is bright, and the pun is very much intended!

Merry Christmas, Happy New Year and all the best!