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Graphene and Quantum Dots Turn a Mobile Device Into a Heart-Rate Monitor

A transparent and flexible photodetector made from graphene and quantum dots demonstrates its capabilities

2 min read
Graphene and Quantum Dots Turn a Mobile Device Into a Heart-Rate Monitor
Image: Dexter Johnson

The Mobile World Congress (MWC) held in Barcelona, Spain, last week hosted a Graphene Pavilion that included a number of research institutes operating under the umbrella of the Graphene Flagship, the European Commission’s €1 billion ($1.1 billion) investment aimed at centralizing graphene research throughout Europe. There were some other companies at the event that are not directly tied to the Graphene Flagship, such as Haydale and Zap&Go. (I visited both booths and posted videos that described their technologies.)

Another booth I visited while at the MWC was that of the Institute of Photonic Sciences (ICFO) in Barcelona, Spain. While this blog has covered a fair amount of the research coming out of ICFO over the years, our coverage has mostly followed the more long-range research projects that have attempted to leverage two-dimensional materials and plasmonics for the creation of a new generation of integrated circuits based around photons rather than electrons.

The prospect of integrated photonic circuits based on plasmonics remains firmly in the future. But ICFO was demonstrating what it has been able to fabricate based on its work with graphene and quantum dots. Essentially, what researchers there have built and demonstrated (see the video, below) is a transparent and flexible photodetector.

Last year, we reported on other research out of ICFO in which they developed a graphene-based photodetector that was capable of converting absorbed light into an electrical voltage in less than 50 femtoseconds, bringing switching to the brink of terahertz speeds. And, four years ago, we covered ICFO’s work in combining graphene and quantum dots, which, at the time, they believed would be ideal for automotive night-vision technologies.

We can only speculate on how this latest technology ties into that previous research. When asked if a description of the underlying technology had been published anywhere, the researchers explained that it hadn’t and that they could not provide any further details until it has. 

Nonetheless, the demonstration of the technology did capture the imagination of many folks visiting the booth. One of the applications that ICFO has devised for the transparent, flexible photodetector was as a heart rate monitor. You can see the demonstration of the technology in the video.

Basically what happens is that when a finger is placed on the photodetector, the digit acts as an optical modulator, changing the amount of light hitting the photodetector as your heart beats and sends blood through your fingertip. This change in signal is what generates a pulse rate on the screen of the mobile device.

It was a nifty application of the technology and certainly inspired a lot of gee-whizzes from those who saw it. However, the ICFO researchers didn’t really envision this as a shot at a viable commercial technology, but more of a demonstration of what is possible. I wasn’t quite so sure that they should have been so dismissive. It seemed to me like it would be cool little technology to have on one’s mobile device. We’ll have to see what they publish, maybe they envision a better application potential.

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Two Startups Are Bringing Fiber to the Processor

Avicena’s blue microLEDs are the dark horse in a race with Ayar Labs’ laser-based system

5 min read
Diffuse blue light shines from a patterned surface through a ring. A blue cable leads away from it.

Avicena’s microLED chiplets could one day link all the CPUs in a computer cluster together.


If a CPU in Seoul sends a byte of data to a processor in Prague, the information covers most of the distance as light, zipping along with no resistance. But put both those processors on the same motherboard, and they’ll need to communicate over energy-sapping copper, which slow the communication speeds possible within computers. Two Silicon Valley startups, Avicena and Ayar Labs, are doing something about that longstanding limit. If they succeed in their attempts to finally bring optical fiber all the way to the processor, it might not just accelerate computing—it might also remake it.

Both companies are developing fiber-connected chiplets, small chips meant to share a high-bandwidth connection with CPUs and other data-hungry silicon in a shared package. They are each ramping up production in 2023, though it may be a couple of years before we see a computer on the market with either product.

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