NHS England estimates that around 250,000 people in the UK have had part or all of a limb removed. Prosthetics have improved significantly in recent decades, yet around a fifth of these amputees refuse to wear them and, of those who do, many are dissatisfied.
At least one reason for this dissatisfaction is that prosthetic limbs don't give the wearer any 'feedback' about the things with which they come into contact. US company Atom Limbs is trying to address this issue with the Atom Touch, a 'mind-controlled' prosthetic limb slated for release in 2024. When someone's arm is removed, the neurons that once connected to their hands may still be in place and can still send signals from the stump to the brain. The Atom Touch has movement sensors in its hand, and these transmit electrical signals to the wearer's stump via electrodes. That can tell their brain that the prosthetic hand is in contact with something, giving what the firm calls a "basic" sense of touch.
Further ahead, special 'e-skin' could prove revolutionary for prosthetics-wearers. In May this year, researchers at the Bao Research Group at Stanford University announced the invention of an artificial electronic skin that's stretchy, paper-thin and durable. The e-skin contains mechanoreceptors that can sense pressure, vibration, heat and cold and can transmit this information as electrical signals. The e-skin could, in future, be wired into a wearer's nervous system via implants, giving them something akin to 'real' touch.
Industrial robots have been around for decades. But the kinds of tasks they do are relatively 'basic' – things like welding, stamping, picking and packing. This is because jobs that require dexterity are essentially off-limits. Robot hands struggle with judging the appropriate weight or pressure required to interact with delicate or slippery items.
This is where an invention from researchers at the University of Bristol could help. TacTip is an artificial fingertip which can produce electrical signals that are much like the nerve signals you find in the human body when it touches things. The team 3D-
printed a mesh of tiny, inward-pointing pins (called 'papillae') on the underside of a polymer 'skin', which mimics the papillae in our own skin. As the angles of the papillae were distorted when they 'touched' items, they sent electronic signals that could tell the machine about pressure and resistance.
Robotic hands that include this kind of 'skin' could potentially sense change much more subtly and adjust the level of grip they apply. For example, when picking up a strawberry, a dexterous robotic hand could perhaps sense the item squashing and reduce pressure.
Image credit: Stocksy ATOM LIMBS
Many jobs can be done remotely today. Being a surgeon isn't typically one of them. From delicate scalpel work to the physical pushing and pulling of body parts, it is an inherently tactile job.
Nonetheless, there are at least some kinds of surgery that can now be done from a distance. For almost two decades, some physicians have been using robotic surgery systems controlled by a surgeon sitting at a monitor who uses special handles to move cameras and instruments inside the patient's body. Typically, the surgeon is in the room with the patient, but could, in theory, be anywhere. The problem with robotic surgery is that surgeons can only see what's happening with their tools on a screen – they can't feel pressure or resistance but must judge what's happening based on live video.
The Senhance Platform, from US company Asensus Surgical, aims to give robotic surgery systems more of a sense of touch. Sensors on surgical robots' arms register pressure and movement. This then sends haptic feedback to the surgeon's hands through the handles they use to operate the robot. This could potentially make remote surgery safer by reducing the risk of accidental damage.
"Buttons are really practical when you're driving," says David Richard, marketing manager at French touchscreen start-up Hap2U. Anyone who's driven a new car in recent years, however, will know that most manufacturers are trying to design buttons out and replace them with ever larger touchscreens. Big touchscreens look good but can also be a pain when you're trying to turn the radio down and can't find the slider in the menu. Besides being annoying, this is also dangerous, Richard says. A recent Swedish study found drivers spend up to four times longer interacting with touchscreens than with traditional buttons – and that means they're not concentrating on the road.
With traditional touchscreens in phones, tablets and cars, Richard explains, a tiny motor is placed inside the device, and it vibrates the entire screen when you touch it. While you can vary the force and tempo of a vibration, this is still a fairly rudimentary way of interacting.
Hap2U takes a different approach. The firm uses piezoelectric actuators, which are placed along the sides of the screen. When the user touches a specific part of the surface, the actuators can be programmed to vibrate the surface at that specific point, and this can give a much richer sensation. In a car, for instance, when a driver touches the volume 'wheel' on their infotainment touch screen, vibrations are sent in such a way that it feels almost as if they're touching a twisting wheel that protrudes from the screen. That way, they needn't take their eyes off the road to find the thing.
A video on Hap2U's YouTube channel shows people sliding their fingers across an image of a fish on a touchscreen. As people slide their fingers one way over its 'scales', the vibration is minimal. But when they slide their finger against the grain of the scales, the piezo actuators vibrate more, giving people a sense of friction and roughness.
Image credit: Owo
If seeing and hearing video game characters getting stabbed, shot, clawed or beaten just ain't visceral enough, then OWO Games' Second Skin might just do it for you. The Spanish company has developed a haptic shirt that delivers a smorgasbord of sensations for game players. The shirt delivers a range of vibrations and movements at different intensities via haptic pads across the wearer's chest, midriff, back and arms which correspond with what's happening on screen (or your VR headset).
From fairly mild sensations (a gust of wind, bumping into things) through to rather grislier terrain (bullet entry and exit, insect bites, punches), the wireless shirt promises to make gameplay more immersive than ever before.
Although many of the technologies listed here remain at a fairly experimental stage, innovations are coming in thick and fast – and we could just be in touching distance of technologies that really transform this complex sense.
What is the sense of touch?
"I always find it useful to think of these things in the evolutionary context," says Dr Guy Bewick, a researcher at the University of Aberdeen's Institute of Medical Sciences. "Your nervous system has evolved to detect change, so that you can detect danger. If something crawls on your skin, you're aware of it right away and immediately look at it. If it's a scorpion or a spider, you brush it off immediately!"
Dr Bewick studies mechanical sensation, and particularly the proteins inside our nerve endings. Different proteins are specialised at detecting specific kinds of changes, including temperature, pressure, location and vibration.
Dr Bewick explains that some receptors in your skin notice vibration. Say you pick up a mug of coffee; if the mug starts to slip out your hand, you'll feel these vibrations and hold on tighter. Others detect location – which part of your body is the mug touching? They also notice temperature – you'll immediately get a signal if your finger moves from the handle to the hot cup itself. There's a lot of complexity here. For instance, some vibration sensors are attuned to rapid vibrations (the mug sliding out your hand), others to slower vibrations.
All this information is then sent via nerves to your brain, and melded together so you know where the mug is, how it feels, and any changes that happen.
