The patches are vibrating, but humans perceive static and low frequency forces mostly.
This create a haptic metaphor which always sucks.
The rest is easy, or easy to figure out.
Never heard telehaptics as term in my whole life
Can you expand on the static and low frequency? My impression was that if you're aiming for fingertips, higher frequency has more resolution. Iirc braille is mostly sensed by the vibration of the ridges of your fingerprint, when moving your finger over the dots. For this reason single character braille displays never really took off, you need an entire row (typically 40 characters) to make a usable refreshable braille display.
I've looked at the actuator array in the paper
https://www.nature.com/articles/s41528-022-00216-1
It's made with "standard" multilayer pzt actuators, with a displacement of 1000nm at 60V. That's apparently above the sensing threshold, but imho not enough for practical applications.
I am curious about the fabrication methods though. The 1mm actuators are in a checkerboard pattern, and apparently reflow soldered. I'm curious how they did that while staying below the curie temperature of the actuators (typically <150°C for PZT), and if that is mechanically sufficient.
It's still very impressive work.
Perceptual modes are specific mechanical stimuli we learned to recognize as specific sensations.
Some of them are: stiffness which is skin indentation and tendons strain in function of space, vibrations which is skin indentation in function of time for frequency above 10/20 hz.
These modes resides a bit on the neurophysiology of touch (how mechanoreceptors respond) and a bit on how we learned to recognize touch sensations.
The problem reside that the first thing you want to do is manipulate, not simply touch.
Manipulation is a bitch because it mostly needs small indentation of the skin which are 1-3 mm of continuous displacement at 1 mm resolution under the fingertip.
They piezo they are using displaces 1 mm at the resonance frequency, I imagine 150 hz (I believe?) or something similar, not in continuous (again, I believe).
Which means that a contact on the sensor is rendered as a local vibration, which requires a lot of mental gymnastic to think of it as a contact.
That is the haptic metaphor. Basically you expect an indentation and you get a vibration, and this sucks and for users.
If they got it in static displacement that is cool and might be something noteworthy
I was not able to locate the frequency response profile of the actuator, which is what really counts.
Rapid moving sensations are really not an issue in todays market.
I hope one day someone comes up with something there which does not requires a backpack of pumps like Haptx.
That moment is when magic will happens in haptics
That's just piezo's, you need to stack several layers to get a usual displacement. You do get high force, so they're typically used for high precision positioning.
I've been looking at piezo bimorph actuators as used in braille displays. Because they're cantilevered you're trading displacement for force (and size). That could perhaps be used to create a high resolution array with enough displacement at low frequency. Not really wearable like a glove, but certainly portable.
Can’t at 10 Hz.
It is the usual stuff.
Check out the work of Vincent Hayward on cantilevers and piezo.