Your Smartwatch's Heart Rate Monitor Was Developed by a Furry

Your Smartwatch’s Heart Rate Monitor Was Developed by a Furry

Twenty years ago, heart rate monitors were single-purpose, dedicated devices focused on health and fitness. Today they’re incredibly common and built into just about every major fitness tracker and smartwatch, thanks to the development of the optical heart rate sensor. There’s a good chance you’re wearing one now, but here’s something you probably didn’t know about the technology: It was invented by a furry.

David Benaron, MD, is a biochemist, inventor, and entrepreneur. He studied at Harvard and MIT, taught at Stanford, and has founded and served in the C-suites of multiple biotech companies. He developed the sensor that enables heart rate monitoring on wearables like smartwatches, and has made advances in the field of optical blood-oxygen monitoring as well.


This is Dr. David Benaron.

He’s also a cheetah named Spottacus and a regular at furry conventions, often kitted out head-to-toe in a fursuit. 


This is also Dr. David Benaron, aka Spottacus.
(Photo: Kory)

In case you’re unaware, a furry is an enthusiast of role-playing an anthropomorphic animal-person. We should note here that fursuiters are a specific subgroup among furries. Not every furry actually dresses up like a big fluffy animal for conventions and gatherings, which is a common misconception; that specific type of furry is known as a “fursuiter.”

Spottacus(Opens in a new window) got on my radar through Twitter. I have several friends who are furries with online presences, and one retweeted Spottacus talking about green light heart rate sensors a few weeks ago, which piqued my interest. Obviously, simply claiming to have invented such a technology is easy to do on social media, so I reached out to him regarding his research and then dug into records to confirm what he told me.

Of course, technology and consumer-ready electronics are almost never a single step between conception and execution, and Dr. Benaron’s work is a particular link in a chain of advances that have led to the ubiquity of smartwatch heart rate trackers. However, his specific research at Stanford seems to be a particularly important step in the evolution of the bulky chest bands and red light/infrared heart rate monitors to what we much more commonly wear now.


Dr. Benaron’s Technical History

Dr. Benaron attended graduate school at Harvard and MIT in their Health Studies and Technology programs, and he received his Doctor of Medicine degree from Harvard Medical School with a specialization in medical devices. He later joined Stanford’s Department of Pediatrics’ Neonatal and Developmental Medicine division, where he taught and researched for over a decade. Dr. Benaron founded Stanford’s biophotonics lab, which made numerous advances (and made mice glow(Opens in a new window) in the process).

He invented the green light oxygen monitor(Opens in a new window) in 2005. It uses green light to measure oxygen in the bloodstream, a different process from the conventional pulse oximeter’s (invented in 1978 by Dr. William New, another Stanford professor) use of red light. This green light-based sensor is the underlying technology that drives heart rate monitoring features in consumer devices like smartwatches and fitness trackers.

Dr. Benaron founded multiple biotech companies, including Spectros(Opens in a new window), a firm that specializes in medical sensors. He also served as Jawbone’s Chief Medical Officer before the company’s dissolution. He is currently Chief Medical Officer at all.health(Opens in a new window) and both Strategic Director and interim CEO of Mor Digital Pharmacy.


Dr. Benaron’s Furry History

Dr. Benaron assumed the name Spottacus in the 90s, joining the then-fledgling furry community. At his friends’ suggestion, he attended his first furry convention, Further Confusion, in the early aughts. He has since been active in furry communities. He chose the name “Spottacus” as a play on the name “Spartacus” said in a Brooklyn accent, and because he tends to favor spotted cats.


Left to right: Spottacus in Beastcub Saber and Heuler Wolf fursuits
(Photos left to right: Tracey Barbutes Photography, Abrahm Lion)

Despite his name, Spottacus’ first fursuit was of a wolf. He does not create his own fursuits, but commissions other experts in the field to build them. His fursuits often use 3D printed materials and custom fur manufactured by National Fiber Technology (NFT, founded long before non-fungible tokens were coined). He currently owns 46 fursuits.

Spottacus produced an art installation, “Soulmates,” at Burning Man 2019. It consisted of six art pieces illustrated by different furry artists, printed on six-foot-tall cloth sections and suspended on illuminated tubing frames.


Jabari the serval
(Photo: David Benaron)

Spottacus currently lives in the San Francisco Bay Area. He has an animal sanctuary permit for his home, and has three pet cats, including an African serval named Jabari.


Talking With Dr. Benaron

I spoke with Dr. Benaron about his career in biotechnology and his life as a furry.

How did you develop the technology behind green light heart rate sensors?

Every scientist stands on the shoulders of those before them, nothing comes completely from a vacuum. 

Before I worked on the heart rate sensor, there were pulse oximeters that measured finger oxygenation. There were even PhDs granted to study how photons bounced around in tissue in a dozen places: Boston, Cambridge, Vanderbilt, Philadelphia, Ontario, London, Berlin, and my new lab at Stanford in both the schools of medicine and physics. So we were very deep in understanding how light behaves in human tissue.


Samsung Galaxy Watch4
(Photo: Angela Moscaritolo)

We knew Hemoglobin absorbed the most light per molecule not in the red, but in the purple and green light bands. But everyone already knew that green and purple light didn’t go through tissue. Did you ever shine a red laser pointer through your finger? The whole finger glows red, but if you shine blue or green light, nothing can be seen coming through by eye. So, red and infrared light were already used because those wavelengths shined through tissue. But absorbance was weak in the red, so you needed to shine all the way through the finger. Nobody bothered to look at green.

My insight was that if you looked at skin, such as Caucasian skin, it looked pink to your eye, and it turns white when you press down. Anything that looks pink reflects red and absorbs green, and if the pink could be pressed out that must be blood. That meant the conventional wisdom must be wrong. Red and green light must have reached blood under the skin, but just the red light visibly came back. If green light could get into skin, there must be some coming back, even if we don’t see it well by eye.

So we tested this idea. We shined white light on skin, and used a sensitive spectrophotometer to measure what came back. And when we measured the returning light, we saw green light pulses! As your heart beats, and the pressure in your blood vessels rises and falls, the size of the vessels change, giving rise to heartbeat pulses in the detected light.

And this not only worked in pale skin, but it also worked the deepest, darkest skin too, even though your eye couldn’t see it. Deeply brown skin looks neutral to our eye, but the light coming back is actually still pinkish from the blood from a spectroscopy viewpoint, and it had the same green pulsing signature of hemoglobin.

When we saw that, we got really excited. We had discovered a simple way of measuring the pulse using reflected light. I drew exclamation points all over the lab notebook page,

Later, we found you could also measure respiration rates, and even estimate blood pressure using this approach, and the smartwatch heart rate sensor was born.


Fitbit Charge 5
(Photo: Angela Moscaritolo)

You also have a patent for white light spectroscopy which can measure oxygen saturation. Is this the technology used in recent smartwatches and heart rate trackers that have SpO2 sensors?

My lab looked at light in human tissue, so we studied many wavelengths from ultraviolet to infrared. Each color of light is absorbed differently by different substances, so water or the pigment for jaundice could be measured. Also, when you use a lot of wavelengths, such as white light, you don’t even have to have the sensor in contact with skin, so you can even measure from across the room because a large number of wavelengths lets you solve the equations accurately without contact. Some of the Microsoft gaming systems adopted this non-contact method.

Because our idea and approach were novel and unexpected, there were over 100 patents issued.

For example, knowing green light can pass through tissue led us to put firefly and glow-worm genes into cells, and then image or count them. We didn’t know if it would work at first. Sitting in a pitch-black room at Stanford, my post-doc and I stared at a Petri dish streaked with the genetically transformed bacteria that his wife engineered. Slowly, our eyes adapted to the darkness, and we began to see the faint colonies of glowing green bacteria.

At that instant, I knew we could change biomedical imaging by noninvasively sensing small populations of these genetically labeled cells in the bodies of living animals. Later, as the full implications of this event became clear, I remained awake well into the night.

You see, most medical imaging methods like CT scans or MRI need millions of cells to detect a group of cells inside the body (if cells are just 10 microns across, then 100 of them form a 1-millimeter line, and a million is just a 1-millimeter cube). But our method could see just 1-10 cells inside a living body. A lot of biology research now uses our light-creating genetic and imaging techniques. In this area, several Nobel prizes were awarded. We were the first to detect and image these genes in non-transparent animals. I think Stanford should have won one of those Nobels, but of course, I’m biased—I’m just super proud of what we developed, and how much of lab science we influenced.


Spottacus in tiger suit
(Photo: Saigon Komodo)

What drew you to furrydom? When did you start?

As a child, I didn’t relate to my peers socially. Everyone else made eye contact, while I tended to look away. I couldn’t understand why they found certain things important. The boys liked sports, while I liked reading. I felt very “alien.” I worried, “will I ever fit in?” I related to animals, though. I loved cats and dogs and wild things. I crawled on all-fours and purred and meowed.


“Fursuiting breaks down social barriers. People you don’t know will start conversations on the street and in restaurants.”

So I started making costumes to recapture those feelings. My first full suit was a wolf. When I put it on, the world got quieter and softer. People tell me I just light up when in a [fur]suit, and I can even focus my mind better. Nobody notices I glance to the side when I listen or struggle to catch my gaze. And I even listen better in [fur]suit.

Now you might think walking around in character creates distance. It’s exactly the opposite.


Spottacus and friends in San Francisco
(Photo: David Benaron)

Fursuiting breaks down social barriers. People you don’t know will start conversations on the street and in restaurants. When I go out to concerts, everyone wants to dance. And on the sidewalk, people will hand you their babies and ask to take pictures. Just think of that. Imagine them doing that when I’m not in [fur]suit?

I was living a furry lifestyle, going to concerts and suiting, but doing it alone. Remember, this is before web 1.0, so there was little available online. And I wasn’t playing Dungeons & Dragons, attending science fiction conventions, or majoring in engineering, places where the early furs gathered. When I suited to dances and concerts, I was the only one there.

Encouraged to come to a convention by these new online friends, I went to Further Confusion, a furry convention, in the 2000s, and it felt like I was finally home. I found words for what I felt. I found friends and a network. It quickly expanded. There was no learning curve, I had found my tribe.

The experience that many furries and other young people who don’t follow the common path is a feeling that we are perennial outsiders in society. And as young adults, we feared that everyone else had dance partners but we may never find love and acceptance. It’s how I felt in elementary school and even junior high. Not that I was unlovable. That I would never find a soulmate. 


Spottacus’ fursuit closet and storage containers
(Photo: David Benaron)

Finding a community where you belong is very important. Whether it be as a geeky engineer you find a Dungeons & Dragons club, or you find that you are a furry like me, finding acceptance is an amazing and fulfilling journey. The furry aspect turned my life from scientifically amazing to socially amazing. Finding my tribe was transformative in my life.

How do you express your furriness? Day-to-day, on social media, at cons? Do you keep it heavily separated from your work, or do the lifestyles mingle?

This is Silicon Valley. I fursuit at work. Sometimes when I [fur]suit at work, no one even comments. I do think it adds street cred, because it is seen as edgy.

As a Silicon Valley executive, I used to take my work team out to upscale restaurants in-fursuit. I’ve even raised venture capital in-fursuit.


Spottacus on a Zoom call in Saber Fur fursuit

I was eating dinner at Shizen, an upscale sushi restaurant in San Francisco with my team from work. I’m in [a] cheetah [suit], made on a computerized loom from a pattern scanned from a live cheetah woven onto a thin stretchy base. it clings to me like a glove, So you see just a living, breathing cheetah. Who is able to eat in [fur]suit.

So there we were, eating, drinking, and I look up to see a balding, middle-aged, blue-eyed businessman standing there. He said he’s from Chicago, and “what’s with the suit.” So, I explained I’m a furry, and this is my team from my startup. He said, “I’m a venture capitalist.” And so we talked. Six weeks later, he invests.

This became a legend at work, so people at work think my suiting is cool.


“I explained I’m a furry, and this is my team from my startup. He said, ‘I’m a venture capitalist.’ And so we talked. Six weeks later, he invests.”

I love the energy of the community. Artistic and scientific talent abound. We produce music, science, and art, and we freely share our ideas and experiences online. I have friends all over the world. I truly feel I am part of the local as well as international furry community, and how many people can say that these days?

Do you have any particular favorite scenes, groups, cons, or just furry experiences you’d like to share? 

When fursuiting was less common, I was often the only suiter at larger concerts. I would get conversationally spoken to by the performer, miked and onstage, frequently. 


Spottacus onstage at a Chvrches show
(Photo: David Benaron)

Before the pandemic, I went to see Caravan Palace, an electro-swing band, in concert. I wore a spandex golden ocelot, with large green eyes and a fuzzy tail. People liked it and pushed me to the front. Thousands of people were there, but onstage the lead singer, Zoe [Colotis], she talked to me. She praised my paws, she asked “who are you?”. When she left she thanked the city, and then added “Bye Furries.”

(Note: The music video for Caravan Palace’s “Lone Digger”(Opens in a new window) revolves around anthropomorphic animal characters. It has over 342 million views on YouTube.)

Imagine Dragons invited me backstage. Lady Gaga waved and said, “hi to my furry and scalie friends.” Coldplay said they liked my dancing. The Decemberists lead singer Colin talked to me about life. I’ve been pulled on stage in front of 20,000 people to dance with Jared Leto, and CHVRCHES. The list goes on.

I was cast as a furry (along with others) in a music video for “You Are Killing Me”(Opens in a new window) by The Dandy Warhols. The video is about a washed-up, alcoholic author who strikes his head in a fall at a bar. He awakens in a furry world, and in the process somehow finishes the novel he has struggled to complete.

As an inventor and engineer, have you ever been inspired by fursuit-making to develop some new technology? Has your engineering knowledge led to any fursuit revolutions?

Yes and no. I have commissioned other makers to push boundaries and be creative, such as custom-woven, 3D-printed fursuits made of poured plastics or foam. These would allow customized, exactly fitted designs to be rendered in 3D and then produced.

But I do think the furry experience is going to change the world. Just as the fandom allows you to choose how you present yourself, technology is accelerating our options for transformation. In cyberspace, a term coined by William Gibson, we work and play in a virtual environment. Our Internet has come to be that place we can meet digitally and has made it real. 


“Whether it be as a geeky engineer you find a Dungeons & Dragons club, or you find that you are a furry like me, finding acceptance is an amazing and fulfilling journey.”

Our avatars, a term coined [by Neal Stephenson] in “Snow Crash” are projections of our transformed bodies, our digital selves presenting themselves to others in a virtual (or augmented) reality, no fursuit required. Starting with Second Life, but now in VRChat and many games, we all now regularly meet in imagined, transformed form. Even video conferencing has digital filters to transform what we show and share with others about ourselves. And in virtual space, the dopamine and serotonin neurologic responses that we have there are as real as in the [real] meatspace world. 


Spottacus in Zarath the dragon suit
(Photo: Sisaro Anh)

I suspect that VR and AR will now draw much of the non-furry world into the furry experience, so I think technology is already there for full transformation.

Now, what about genes? Genes don’t exist in a vacuum. We form and become real after a number of genes have interacted over time to grow us into a species. Yet, we know certain animals are capable of organ or limb regeneration. Others are capable of full transformation, such as when a caterpillar liquefies to rearrange and reform organs to become a moth.

So many, if not all, of the genes and mechanisms are already there. It is therefore just a matter of time until direct evolution allows us to intentionally grow tails or fur. It will just take some time for us to get there, so we don’t accidentally introduce unhealthy mutations or cancer, but it is coming.

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