To toughen screen glass, it is dipped in a bath of molten potassium salt at around 400 °C. Larger potassium ions take the place of sodium ions at the glass surface. Squeezed in, they create a compressed layer that stops tiny cracks from opening. This “ion exchange” principle, developed in the 1960s, makes the glass several times stronger.
In 1843, inventor Alexander Bain patented a way to send images over telegraph wires using synchronized pendulums. By the 1860s, a commercial fax service was already linking cities. The telephone wasn't patented until 1876, more than three decades after that first fax patent. The fax is really a child of the telegraph age.
On 8 October 1958, in Stockholm, 43-year-old Arne Larsson received the very first implanted pacemaker. The device, designed by engineer Rune Elmqvist and implanted by surgeon Åke Senning, worked for only a few hours and had to be replaced. Larsson went on to receive more than twenty pacemakers in his lifetime. He died in 2001 aged 86, outliving both the engineer and the surgeon.