Friction simulation on touchscreen | Hacker News Reader

Friction simulation on touchscreen

cnettv.cnet.com

61 pointscr4zy18 comments

Oddly enough, I think I know exactly what this feels like because I have felt something like this on a laptop that was plugged into an ungrounded outlet. The metal surface felt like it had ridges as I dragged my finger across the surface... 60hz ridges. When my finger wasn't moving if felt no different. When I unplugged it, the sensation went away.

I've noticed that a few times myself. Most noteably badly grounded proaudio gear made the mics feel "rough" when plugged in. Its a well known warning sign that something's amiss and could become dangerous.(1)

I went so far as to make a little medium voltage amplifier and hook it up to my signal generator so I could try various frequencies and powers. Lots of strange and wonderful textures emerged but it always felt a bit tingly, like I was getting a mild shock. Hopefully they've figured out how to keep this from happening while still keeping the good part.

(1) Every once in a great while someone is hurt or killed touching a microphone connected to a malfunctioning mixer/amplifier.

My dad's XPS M1330 does this. I actually quite like the feeling of mild electrocution. I doubt many other people do though.

My Macbook Pro used to do this, it was odd. The annoying part was that my hand hurt after using it for a few hours.

If this really works with reasonably low power, you can bet the big guys are lining up for a bidding war. This is the kind of feature which an Apple or a Samsung would want to have exclusively, at least for a while.

E.g., Apple seems to have bought all the consumer electronics output of the metal-moldable-like-plastic company (forget the name) a while back, though we haven't seen the results publicly yet.

They are carefully not mentioning battery consumption... i'd expect it to be high for a system that remodulates the electrical charge on its surface periodically.

This would be not just cool, but really useful in terms of usability. I'm surprised there are so few upvotes...

Any idea if this works with more than one finger at a time?

For stationary setups, this is for the first time a real win for touchscreens in comparison to a conventional screen plus a pointing device (mouse, trackball, you name it). I'm really curious what they'll make out of this.

I would love to have a touchscreen keyboard with this functionality in it. This is the biggest thing missing from touch screens presently. Very excited to see what comes from it.

It uses Coulomb's law, a principle of attraction between electrical charges:

http://senseg.com/technology/senseg-technology

Physics behind it:

http://en.wikipedia.org/wiki/Coulomb%27s_law

I still don't understand. How does running a current through an electrode produce an attractive force to a finger? The finger isn't going to have positively charged particles in it.

A net neutral finger is still composed of negative and positive particles. Remember that the negatively charged particle (electrons) are relatively mobile. If you apply an external electrostatic gradient across a region, you end up with those electrons moving.

So is this a repulsive or attractive force? Can you control that?

Attractive only.

If I remember my electrostatics, the rationale is that if the surface becomes positively charged, the positive charges in your finger will move away from the surface, leaving only the negative charges near the surface. Those particles will be attracted to the screen. If you reverse the charge so the surface is negatively charged, then the negative charges in your finger will be repulsed, leaving positive charges which will be attracted to the screen. Either way, your finger gets attracted to the screen.

This is amazing. I've never heard of this before. I can think of millions of potential applications; make car tires stick to the road when cornering, replace seatbelts with a electric car seat, glasses that stick to your face, a phone that sticks to your ear, shoes without laces.

I'm sure I could come up with a lot more ideas too.

For more detail (and to correct my previous post a bit), in materials with low electron mobility (aka insulators), what happens isn't so much the movement of charge carriers, but rather the orientation of each atom's electron field. Basically, by imposing a strong gradient, it will cause each individual atom's electron cloud to reorient/shift, which causes each atom to set up it's own little gradient which points in the opposite direction.

You sum up those little reorientations amongst all particles in the material, and you end up with a net electric field that points in the opposite direction, which then becomes attractive.

The above is a bit more accurate description of what happens in insulators (which accurately models some parts of our skin), while a-priori's description fits the conductor parts (most of the wet bits) of the human finger better. And obviously, this is just an approximation/model of what's going on.

So is this an effect I can create on my Arduino? How do I go about setting it up?

Reply on news.ycombinator.com