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Imagine doing your dream job at the age of 91 - that's what Barbara Knickerbocker-Beskind, a designer in Silicon Valley, is doing. She talks about her life long passion for inventing.

During the Depression we had no money to buy anything, so we were all problem-solvers right from the beginning - there was no way around it, we had to be. We made everything except shoes and glasses.

My father was one of the first 100 men to work for the FBI, but when I was about a year old he lost his job and had no work for seven years. We moved in with my grandmother. Can you imagine a toddler being brought into a house of an 80-year-old who didn't like kids? She never smiled. But I was very happy with my parents. My father was a keen observer of his surroundings and imparted that to me. My mother was very creative, and I followed suit.

We didn't have money to buy toys so we used to make our own. I put two car tyres together to make a hobby horse - I learned a lot about gravity because I fell off so many times.

I knew by the age of 10 that I wanted to become an inventor, but I was told by my vocational adviser at school that they didn't take women in engineering school, so I went into home economics, thinking maybe they needed someone to design new can openers. Well, that wasn't true.

When I graduated in Applied Arts and Design from the Home Economics School of Syracuse University in 1945 I was very fortunate to be accepted in the Army's Occupational Therapy (OT) training programme. That really launched my career.

Find out more

• Barbara Knickerbocker-Beskind spoke to Outlook Listen to the interview on iPlayer
• Listen to more extraordinary stories from Outlook on the BBC World Service

At that time occupational therapists would use craft materials - weaving, carpentry, leather work - to activate the hands and legs of patients who were coming back from the war.

As an occupational therapist (OT) in the army there were many things I had to devise that were unique to each person's needs, both to adapt the equipment to the patient, and to adapt devices for them individually to make them independent and able to hold a spoon, a fork, a writing utensil.

We had many polio epidemics at that time.

One of my polio patients stands out for me: a flight commander who left Hickam Field in Hawaii with a squadron of nine planes - he got sick so fast that by the time they reached Travis Air Force Base in California he was already paralysed. They had to unbolt the pilot's seat to lift him out, and he never walked again. I worked with him, helping him to use long leg braces, and designing an apparatus so that he could stand and work at a table.

He was among many patients at Walter Reed Army Medical Centre, where I was stationed for three years - during polio epidemics any soldier, air corps personnel or dependant who lived east of the Mississippi came there. Those west of this point were treated at Letterman Army Hospital in San Francisco.

In 1966, aged 42, I retired from the Army as a major and went into private practice, the first occupational therapist in the US to do so - I'm always a pioneer.

I worked with children with learning disorders. I wanted to develop equipment that would appeal to them but also help improve their balance.

I patented an inflated square pillow, about 3ft high, with rolls around the outside that protected children when they fell - I called it a space ship. It was fun for them, but it also improved their sense of balance.

When I got married at the age of 52 my private practice flourished, because we built a separate building that housed my then-husband's practice of psychotherapy on one side and my OT practice on the other. In 1984 we moved from New Jersey to Vermont and I was a consultant for the school system there.

I tried to retire five times - as an OT, as a private practitioner, as an author - but it never works. I went back to school to become an artist in 1997 and that has been helpful in drawing my inventions.

In 2013, I saw David Kelley - the founder of the design firm IDEO - on the TV programme 60 minutes. When I realised he accepted, and really respected, people from a varied background, I thought, "I have a unique kind of life experience and designing skills - I could be of value to their firm." I was 89.

I typed a letter, which might have caught their attention because they don't get many communications by "snail mail"- I have macular degeneration so my eyesight prevents me from using computers.

Within a week I got a response. They were just starting to design implements that would be helpful to the ageing, and so it was very fortuitous that I arrived at that time.

They invited me to come in and meet a few people. When we sat down at a table for four in the cafeteria, I thought, "That's very nice but I thought there were going to be a couple more people." What I couldn't see was that behind me people were filing in - about 30-35 designers and engineers. Suddenly, I found myself being introduced as the speaker. I got up and told my story and fielded some very interesting questions.

Designing with real people in mind

• IDEO is a global design and innovation consultancy founded in 1991 by David Kelley, Bill Moggridge and Mike Nuttall
• Steve Jobs was one of their first clients - IDEO designed Apple's first mouse
• The firm's approach to problem-solving is to put together teams from very diverse backgrounds
• Designs always start with how people really behave - they call this "human-centered design"

After that I became an adviser for equipment and designing products and services for the elderly and the low-vision community.

Every Thursday I walk three blocks to the train station - I know all the conductors now. I arrive at either the Palo Alto or San Francisco IDEO office around 10:00 and often sit on the same sofa, so that everyone knows where to find me. Word spreads from the front desk and people will arrange appointments with me for ongoing client projects. People will also stop by to talk about what is going on with various projects - it's an extremely collaborative environment.

I love working in this atmosphere. I may be six or seven decades older than some of the people I'm working with - and many of them have PhDs or masters degrees, which I don't - but I'm accepted as an equal. My voice is respected for what I bring to the table, for my experience, for my insights, and for my inventive, problem-solving nature.

For example, for one product - still under wraps - they intended to use batteries, but if these batteries are tiny, like the ones for hearing aids, older hands can't manipulate them easily and they drop them or lose them. My point was that it was better to recharge the product at night, when it is not being used.

No-one can expect, at a young age, to put themselves in the shoes of an elderly person and sense what it's like. Even as close as I am to the issues of the elderly, I have been amazed, and have learned from people whom I live with in my retirement community. I've always said to them, "Come and bring me your ideas of what you need."

There was a gentleman who came up to me recently and said: "Barbara, I need you to invent something for me - I walk slowly on a walker and I don't hear well, so when somebody comes up behind me and slaps me on the back it scares me to death. What can you do to help me? Maybe something that would be like a mirror?" I thought, "Well, that's a no-brainer." I went to the bicycle shop, got a rear-view mirror, attached it to his walker and he is so happy.

One lady said, "The grips in the shower are slippery when you have soap on your hands, we need a rough interior surface." Well, how complicated is that? Then I looked at them very closely and realised they're made for 200lb men with large hands - we need three sizes, with a small grip at the bottom for little old ladies, who have very small hands.

On a personal level - as my central vision is lost, I have no vision of people's faces. I'd like to have a camera mounted on the bridge of a pair of glasses that has face recognition so that as somebody approaches, if they say: "This is Gloria," the next time that person approaches, it says in my ear: "This is Gloria." That way I can meet people and not have to wait until they tell me who they are.

If you're going to design for the elderly, ask them what they need, don't tell them. We don't need pink canes and jewelled pill boxes, we need functional equipment that makes us more independent, keeps us safe and gives us joy.

I think the elderly are an untapped resource, whose input should be sought.

I don't expect everyone to enjoy working the way I do, but if you don't have something that identifies you in a positive light - whether you're the best knitter or someone who can still play the piano beautifully - you lose your identity. And this is my identity - I'm working.

Barbara Knickerbocker-Beskind appeared on Outlook on the BBC World Service. Listen to the interview on iPlayer or get the Outlook podcast.

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