He started to research upper-limb prosthetics and spoke to amputees and people with limb differences about their experiences of different prosthetics.
“The biggest shock for me was the fact that nearly half of people who use hand or upper-limb prosthetics reject them,” Mackie told BBC Radio Scotland Breakfast.
“Over the last 30 years, the industry has focused on robotic hands but it has not had the impact that it would have hoped for on the rejection rates.
“There is still a massive need that is unfulfilled.”
Comfort issues, weight concerns, poor fit and limited functionality are reasons why amputees often stop using their devices.
Mackie said the most popular device for amputees and those with limb differences is still a hook, which was invented in 1912 – the same year the Titanic sank.
Robotic hands, he said, were struggling to replace hooks.
Noticing a gap in the market, the engineering graduate set up Metacarpal in 2020 with the vision to create a hand prosthetic controlled and powered by body motion, without the need for electronics.
