[EricHaptics]

Sure.

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

[EricHaptics]

Ok, I read the article.

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

[JackMcMack]

Displacement is 1000nm, so 3 orders of magnitude less than 1mm. As for frequency response, looks like they tested up to 1000Hz. I see no reason why it wouldn't work at any frequency from 0Hz up to 1000Hz, and even higher. But because the displacement is so small you really need the higher frequencies to be able to sense the actuation.

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.

[EricHaptics]

Yes 1 micron at 150 Hz can be felt.

Can’t at 10 Hz.

It is the usual stuff.

Check out the work of Vincent Hayward on cantilevers and piezo.