FLOWBIO Co-founder Stefan van der Fluit


Startup Q&A is an interview series showcasing health, fitness, and wellness companies.

In this Q&A, we connected with Stefan van der Fluit, co-founder and CEO of FLOWBIO, makers of a biowearable that measures a wide range of performance data from sweat. Stefan explains how nanotechnology and his own endurance sports career converged in the creation of the FLOWPATCH and why serious athletes make the perfect target market.

Can you tell us about what you’re working on at FLOWBIO?

Stefan van der Fluit: We are unlocking the next generation of human performance data through sweat. Our FLOWPATCH is a proprietary biowearable that captures sweat off the skin’s surface and analyses its composition in real-time, starting with water and electrolyte loss.

We have been developing this product in stealth for the last 15 months, recently conducting athlete trials in our performance lab in London and getting data the world has never seen before, namely real-time electrolyte and fluid loss during exercise.

Our biowearable consists of two parts: the sensor module and the shell. The shell contains all the necessary electronics to interpret the signals coming from the sensor, compute this data, and stream the data and hydration recommendations to athletes’ watches, bike computers, or phones.

The sensor integrates microfluidic technology and electrochemical sensors to measure the local fluid loss and sodium concentration, which we scale up to total-body fluid and electrolyte losses via an algorithm.

Our companion app translates this data into actionable hydration recommendations. We’ve spent a lot of time developing sensor technology that not only enables in-the-field quantification but maintains near-lab-grade accuracy, ensuring athletes are provided with the best data possible to make measurable performance differences. For the last year, we have supported elite athletes and teams to perform at the Tokyo Olympics and some of the most grueling stages of the 2021 Tour de France.

As we are taking a full-stack approach here, we can dictate the pace and direction of our product’s roadmap; hydration data is only the beginning. We chose sweat as our bodily fluid of choice as sweat glands are nature’s “built-in” needle — and sweat, in layman’s terms, can be seen as a heavily diluted proxy of blood.

This enables us to create the world’s first multi-molecular quantification wearable without needles. Sweat is data.

How did you come up with the idea? What key insight led you to pursue this opportunity?

SVDF: My background has always been deeply rooted in solving problems through technology. I started this journey when I was still in high school, founding a Web 2.0 strategy agency and helping local businesses transition their organizations from offline to the online marketplace.

Alongside being a product geek and strategy nerd, I went deep down the rabbit hole of endurance sports. My motivation for getting healthy requires a whole other interview, but long story short, I would not be where I am today were it not for the inner-athlete in me.

Slowly but surely, I got more invested in triathlon, falling in love with the sport due to the inability to ever master or perfect it — your triathlete self is always a work in progress chasing that next PB. This was when I was exposed to sports science, physiology, and performance nutrition. I spent weeks researching the latest methodologies for recovery, fueling, etc., incorporating all the learnings into my training plan and nutrition plan.

In 2018, I won the Dutch national championships for my age group at IRONMAN Maastricht — this led me to get a professional coach and explore the path of going pro. I eventually decided against it, as I missed “using my brain” and knowing the isolated existence that is the life of a pro triathlete. However, I decided to integrate all that I had learned on my journey as an endurance athlete and combine it with what I knew best: building products.

My co-founder, Dr. Giovanni Rovere, and I met in the first half of 2020 in London as part of the Entrepreneur First LD14 cohort. Giovanni and I brainstormed a few ideas that would take advantage of both our backgrounds. Given his deep expertise in shrinking biomedical devices into wearable form factors without compromising their efficacy and data quality, we started looking at the next step or evolution of understanding the human body through wearables.

On my journey as an athlete, I learned that athletes are super data-hungry and tend to adopt new technologies years before anyone else if it gives them a data-based edge. Athletes spend a disproportionate amount of money on their hobby: the typical consumer endurance athlete spends $15K per year on their sport. And athletes are insanely religious and loyal, meaning that once they find something which works for them, you have their business for life.

All these things combined make athletes the perfect market to focus on when it comes to building products that deliver human performance data.

How did you turn your idea into a company?

SVDF: We were fortunate enough to be a part of the Entrepreneur First (EF) process, meaning that if you showed enough traction in the early days of your concept, you had your first cheque waiting. Without EF, FLOWBIO would not be here today, as Gio and I would never have met, nor would we have had the incubation period to test the waters of our concept and raise our first few cheques.

After closing our first round in September 2020, we got to work. We built out our engineering team, covering all the bases of the three pillars of FLOWBIO: engineering, physiology, and product. We hired some of the best and brightest electronic engineers, software engineers, chemical engineers, physiologists, and microfluidic engineers who, after nine months of work, got us to a position of holding in our hand what Gio and I had sketched up not too long ago.

While Giovanni and the rest of our engineering team were building the first prototypes of the FLOWPATCH, I was working on securing partnerships and building athlete relationships to validate the need for the FLOWPATCH further.

We are now working with some of the world’s leading sport supplement companies, which at launch will enable us to access three million athletes straight out of the gate. Not only that, we are building up stories of how our data is pushing new limits and accomplishments for both amateur and elite athletes.

This ability to build a team, cultivate a culture, create hardware and novel IP, prove the product need, and build a genuinely original path to market gave our investors and new investors the confidence to close our second round six months after closing our first.

How big can this get? What’s the addressable market and how do you go about capturing it?

SVDF: Let’s first clear the air: The best companies in the world all start with what I call an unknown truth.

Despite the success of Oura, WHOOP, Zwift, Wahoo, etc., 95% of investors still think high-end sport and fitness is a niche hobbyist market with little business opportunity. This is why you see most sport and fitness companies eventually pivoting towards wellness and general well-being as, on paper, this is the larger market and opportunity.

We have a very controversial opinion about our market born out of first-hand experience and unique insights developed over years of being consumers in this space: Technology is NOT going to make you a healthier person, period. Only you and your internal conviction will enable you to be a healthier person and live a consistently healthier life — technology is merely an enabler.

Why is this important? Because when building a consumer product—in fact, any product—the ability to attract a customer is excellent and makes for good PR. Still, the most important thing for any business is retention. And retention comes when people’s genuine needs meet great products.

The unfortunate reality about health & fitness products is the majority go unused because the end-consumer cannot see the value in their day-to-day life and lacks the necessary change in behavior resulting from this missing value creation to follow through.

Taking a step back, the ugly truth is that leading a healthy life is a luxury in today’s day and age. Take the US for example: 48% of people who face an unexpected bill of $250–500 face “bankruptcy.” When you are living so close to the line, the last thing that is on your mind is hitting your macros for the day or what your recovery score is. So, as a company selling products that enable leading a healthier, more optimal life, you can strike off 48% of your market’s population as TAM.

So, is the other 52% your TAM? Unfortunately, it’s not so simple. Everyone starts on the same path: “I want to live a healthy and holistic life.” But somewhere along the way, we all come to a fork in the road. At least 50% return to old habits.

The remaining 50% who stick with it start a journey where, after a few months or years, they no longer identify with the person they were two years ago — they are better, healthier, and more disciplined, meaning the products and services that they used two years ago are no longer good enough for them. They’ve evolved.

As a company, we decided to build products where, yes, the TAM is smaller than the general health-curious consumer market, but the LTV is at least 10x more. This is our unknown truth.

Focusing on human performance data and the “invested athlete,” as we (and Strava) call it, makes good business sense. Strava, by the way, now has 100M+ users, adding 2M a month. I’d say that’s more than enough athletes for us to get hooked on the FLOWPATCH and build a billion-dollar business on.

Who is the core customer? How are you acquiring customers? And how will you grow the customer base?

SVDF: Our initial target market is the endurance athlete. There are an estimated 20M endurance athletes across the US/Europe, and we immediately reach 3M of them via our partner channels.

In the background, we have already begun talks with pro teams and athletes in the NHL, NFL, MLS, Premier League, F1, CrossFit, etc. — so, we see a natural growth beyond endurance sports in the next three to five years.

Alongside consumer and professional athletes, we see a massive opportunity in the industrial athlete space: military, heavy industry, logistics, supply chain, demanding blue-collar jobs, etc. Wherever people are pushing their performance limits, the FLOWPATCH will enable that.

One of the most important lessons learned from my time at Facebook is that you don’t need to build, develop, and finance growth machines all by yourself. You should find partners who share a vested interest in your product’s success and design partnership models which benefit them to “sing your gospel.” This partner-first model makes up a crucial part of our blitzscaling strategy.

Partners, to us, are sport supplement brands who are looking to reinvent the way athletes use their products, event organizers who are looking to transform athlete experience, product partners who are looking to bolster the functionality they can offer their customers, and professional athletes looking to inspire the next generation of Usain Bolts, Alistair Brownlees, and Michael Phelpses.

Looking at your road map, what are some of the milestones you’re targeting over the next 3-6 months?

SVDF: The team is laser-focused on getting the FLOWPATCH into the field, generating revenue, and working to prove PMF through our closed beta, which will be starting H2 this year.

We plan to work closely with our customers to perfect the product experience. The goal is to scale the availability of the FLOWPATCH in H1 ’23. Our logic is that if we can demonstrate >80% retention in the hundreds of athletes, this math will scale to the thousands, tens of thousands, and hundreds of thousands (and eventually millions!).

From our conversations with our customers, we know that there will be no shortage of demand if we can deliver on our product claims. The most important thing for us now is to tweak and improve the product experience to get to that user value which ultimately translates into incredibly healthy long-term retention. It’s a similar strategy our investors from Oura took when building their company.

Anything else you’d like to share with readers?

SVDF: We have just announced our seed round. We are raising $3M, with $2M already committed. If you actively invest in our space and believe that the future of human performance is a sweat-driven one, we’d love to talk.

And if you are interested in being part of the closed-beta for the FLOWPATCH, sign up here.

If you’re interested in having your company featured in our Startup Q&A series, send an email to team@fitt.co.

Related reading from Fitt Insider:
Issue No. 166: Next-Gen Health Wearables

Get the latest health and fitness industry news

Keep up with industry news, trends, investment activity, and job openings — in one weekly newsletter.

    No thanks.