As his obituaries pointed out, my brother David made a name for himself with his unrideable bicycle; his ‘perpetual motion’ machine — a bicycle wheel still rotating in a frame on our mantelpiece (it attracted 1.1 million hits on a German website); and his theory that the arsenic found in Napoleon’s hair and fingernails was down to his wallpaper.

The papers naturally got all this wrong (‘Napoleon killed by wallpaper’ they intoned, as did Andrew Roberts), and the image of the potty prof emerged. In fact, his purpose was serious. He was equally serious about our children — after a failed marriage, he had none of his own, to his great regret — and at lunch every Sunday the idiosyncratic scientist and dedicated uncle came together.

David brought liquid nitrogen so the children could freeze flowers and make instant golden syrup ice lollies. He put a reversed vacuum cleaner in the bath together with Fairy liquid to fill the room with bubbles. He shut the children in the boot of his car, where they would blindly shout out ‘left’ or ‘right’ randomly at junctions just to see where they would end up. Holding on to a rolling pin suspended by loops of plastic attached to the first-floor landing, they stepped off the top of a stepladder on the ground floor and descended slowly to terra firma.

Playing snooker on our small table upstairs presented a challenge. Some balls were not quite circular, or had off-centre weights or liquid inside them. Others contained magnets which reacted with ones fixed under the table, causing them to judder to a quivering halt, or veer wildly off-course.

Shopkeepers too had cause to be on the alert. One day the hapless postmaster was presented with a parcel containing a metal canister filled with dry ice. En route to the post office, it had turned into the world’s first frosty parcel. The postmaster scraped off the rime to read the address, disappointingly thought better of it, and handed it back.

But this was ‘Wicked Uncle David’ for you — ‘wicked’, because the children had been assured from a young age that only villains had beards, and bro had a beard. He adored them, and they him. What connected his research and the children was a sense of mischief and the science of everyday things.

How does a bike actually stand up? (He disbelieved gyroscopic theory, and his research showed how crucial the shape of the front forks was.) How does a snooker ball with a liquid centre react? How on earth could wallpaper be dangerous? If arsenic was once used to colour wallpaper green, how is green produced now? And how about an alcoholic/nicotine/aspirin wallpaper?

Bro’s interest began extraordinarily early. His long-suffering parents bought him chemistry sets and Meccano, and by 12 he was already hard at work in his lab in the greenhouse at the bottom of the garden in Petts Wood, Kent. In papers recovered from his junk- and apparatus-filled home in Newcastle upon Tyne, we found his book of ‘Ideas and inventions (vol. 1) up to 1952’ (when he was 14). No. 1 is for a ‘Magnetic bearing (frictionless)’; no. 9 ‘Tidal energy apparatus’; no. 16 ‘Semi-water gas producer’ — and so on. Each is fully described, with explanatory diagrams and mathematical calculations. Small beginnings: in 1993 Nasa launched bro’s ‘chemical garden’ into space, to discover how it would react in micro-gravity.

One sees here the seeds of a ‘What if..?’ and ‘Why not?’ mentality growing out of an utter fearlessness in experimenting with the world about him. On one occasion, bro lit the fuse of a golden rainbow firework in the sitting room, convinced he could put it out. He couldn’t. He would take anything apart to see how it worked, sure he could put it back together again. He usually could.

Our garden shook with explosions, small cardboard rockets soared into the clouds, and hot-air balloons wandered lazily among the trees before bursting into flames. He produced riotously illustrated boardgames (he was a fine cartoonist). On one occasion decaying chemicals set fire to a wardrobe. Our magnificent parents did not lose faith.

Bro was too independent-minded to hold down a ‘proper job’. His columns, and his work dreaming up experiments using everyday objects for TV programmes here and in Germany in the 1970s and 1980s, kept the wolf from the door (he lived a private, very ascetic life). This enabled him, through his ‘guest’ attachment to the local university chemistry department, to do his own work. A colleague regarded him as ‘one of the few really original people’ there.

Hence too the weekly ‘Daedalus’ column he began in the New Scientist in 1964 while a research chemist at Imperial College (it transferred to the Guardian and Nature and lasted till 2002). Its purpose was to amuse and challenge readers by presenting them with what looked like a useful perversion of nature that Daedalus made to appear scientifically possible. Socks fall down your legs: how about socks that ratchet their way up them? Car tyres thrum as they whirl along the motorway. On the principle of the gramophone, might not the road surface be ‘tuned’ in such a way that anyone travelling over the limit would find the tyres announcing, ‘Slow down, you are breaking the speed limit’?

Some businesses took all this seriously. The anti-gravity sock attracted the attention of a hosiery company; others wanted to license Daedalus’s products. Nor were all the 1,887 columns purely scientific. For example, he proposed computer trading in the City years before it was first attempted.

Bro dedicated his probably unique grip on almost all areas of science to persuading people that the scientific world opened up endless vistas about the wonder of the world and what might be. His vast, detailed correspondence with viewers and readers who wrote to him, witnesses to his determination to promote that cause. Our children’s experience reflected this: it was his close attention to their responses that made him such a transformative uncle.

Thanks to his publisher Pan Stanford, David’s last book, his speculations on the unconscious mind, was delivered a week before he died. In it, for all his understanding of the material world, he admitted: ‘I reckon we know very little about anything that matters.’

In perpetuum, frater, ave atque vale.