When a world famous, multimillionaire engineer who holds 440 patents and owns two jets, two helicopters and a private island tells you to worry, it's probably time to worry. And Dean Kamen is a very worried man.

Quoting HG Wells, he tells me: "I think the world is in a race between catastrophe and education." We're in the corner office of his hi-tech research company, Deka, surrounded by Einstein memorabilia and cartoons of his most famous invention, the Segway electric scooter. "In most cases, catastrophe is winning."

"The polar ice caps, swine flu, energy, the environment: almost every problem I can think of that's going to bite us in the ass in the years to come needs extraordinary technical achievements," says the man whose own achievements include a robotic prosthetic arm and a wheelchair that can climb stairs. "More than ever, the world needs good engineers. However, the pool of talent is shrinking not growing."

That's not all. According to Kamen: "Today's children are the first generation in which it is highly probable that their average quality of life, and education level, will be less than it was for their parents."

No naive solutions

This is not the Dean Kamen I came to see. I came to see the visionary technologist who dropped out of college to develop the world's first mobile insulin pump, the proud inventor who envisaged millions of Segways seething through the world's cities, the iconoclast engineer who, disappointed with teenagers idolising sports stars, created his own sport based on competitive robotics. (Don't laugh: the FIRST championship attracts nearly 17,000 school teams from around the world).

Instead, I got a man whose passion for technology seems increasingly swamped by frustrations with global realpolitik. Take his work on water and power systems for developing nations. "50% of all human diseases are due to water-borne pathogens," says Kamen. "For the few billion people that are sick and dying on a daily basis, the idea that we're going to build them a municipal water infrastructure in the next year, or even the next decade, is profoundly naive. So we set out to develop technologies that can solve the problem of giving people clean water without needing to transform their environment."

Cue Deka's integrated water purifier, codenamed Slingshot. "Here's a box with two hoses," says Kamen. "Dip one in anything that looks wet – an ocean full of salt, a well full of arsenic, a pond full of cryptosporidium, giardia and faecal matter – and out of the other one comes pure drinking water. It's portable so it can be carried into a village, and it's cheap [£1,000] and productive enough so that you can make enough water to share the cost over a few hundred people."

Kamen doesn't pretend Slingshot is home to any ground-breaking discoveries: "We didn't invent vapour compression. We didn't invent the distillation process. We didn't invent any fundamental understanding of the Second Law of Thermodynamics. But we did make a lot of little inventions to make a small scale, highly reliable device that frees us from having to measure what's wrong with the input water. There's a lot of technology in there that we're quite proud of."

He's just as proud of his Stirling engine (a device to convert heat into mechanical energy, first conceived of in 1816), which produces up to 1kW of electricity from virtually any fuel source. "In a trial in Bangladesh, they put cow dung into our machine. It was a multiple win: small, distributed, scalable and using fuel that is otherwise toxic. Whether you burn it or not, cow dung evolves methane, which is 21 times worse than carbon dioxide as a greenhouse gas. So why not capture it and turn it into useful heat and electricity?" Working together, the two devices could boost living standards and save lives across the world. Instead, the prototypes are languishing in Deka's labs. "In order to put them in volume production, you need a well-defined market and a distribution strategy," explains Kamen. "The problem is that most of our commercial partners – even the giants – do not do a lot of business in the underdeveloped parts of the world. This is not a shortage of technology. It's a shortage of courage, vision, awareness: a lot of human things."

Too much short termism

It's this lack of long-term thinking that infuriates Kamen. "Our technology is being squandered on quick buck applications. More and more we seem to be defaulting to the short term. Do we need to double again the rate at which we move data so two kids can play games with even more realistic violence? Or should we be ensuring everyone has at least some access to the internet? The world doesn't need the next generation of videogames."

It might not need them but it seems to want them, which is arguably the opposite of what happened with Kamen's ill-fated Segway Transporter. Kamen thought that his nippy, balancing scooter would "be to the car what the car was to the horse and buggy". He whipped up a media frenzy before its launch in 2001 and invested heavily in factories capable of producing 40,000 units a month. Eight years later, sales of Segway have only just passed the 50,000 mark.

In April, Segway and the bankrupt US carmaker General Motors unveiled a two-man, semi-enclosed update called PUMA (Personal Urban Mobility and Accessibility) with a top speed of 35mph and a range of up to 35 miles. This time round, Kamen is almost dismissive of the new vehicle: "The day we made the first Segway, the very first one, we drew pictures of enclosed ones. Going back and tweaking things to make them 5% better or 3% cheaper? There are whole industries who know how to do that very well. Our position is been there, done that, did it, changed the world, move on."

Talking of moving on, Kamen is now wary of hyping – or even mentioning – his future projects, but he does let one slip. "At Deka, we're looking at a couple of ways to be in the energy business. We're working on solar now and I think the world of energy is going to see a lot of changes soon."

When pressed for more details, Kamen clams up, or rather changes the subject to North Dumpling, his three-acre private island off the coast of New York, which he refers to in deadpan as an independent kingdom. "Dumpling is completely carbon neutral," he says. "We have solar panels on every building, a 10kW wind turbine, our own little Stirling engine for backup power, burning only local fuel. We're making our own water out of the ocean with Slingshot. And we are now developing a foreign aid program to help the US."

A man who wants to re-engineer the whole world for sustainability, one country at a time? At last, here's the Dean Kamen I came to see.