Surface haptics render textures, dials: on-the-fly

Interviews |
By eeNews Europe

Spun out of Northwestern University in 2011 when company’s co-founders Ed Colgate and Michael Peshkin first described their haptic solution in a CHI 2011 paper titled “Enhancing Physicality in Touch Interaction with Programmable Friction”, the startup engineered its haptics around electroadhesion. This effect only relies on surface electrostatic forces interacting with the skin at the tip of your fingers, which under increased touch friction, perceive the same signal as a texture or a pattern protruding out of the touch surface. In effect, the changes in friction are perceived as fine textures, edges and bumps that can be felt without looking although they can be tied to visual representations.

“The way we create electroadhesion is by applying an electric field below the touch interface, which creates an inverse polarity, attracting more of your finger to the surface of the screen. We can modulate that electroadhesion at high frequency and pixel by pixel” explained Tanvas’ CEO Phill LoPresti when interviewed by eeNews Europe. “Physically, when the skin is pulled closer to the screen, it experiences more friction as it slides across the screen.”

In the touch-display stack, the added cost for haptics is marginal as the company leverages the existing patterned Tx and Rx ITO traces below the glass of the touch-panel and only puts additional ITO lines on top of the same cover glass.

Tanvas’ touch and haptics stack.

The bottom layer is for touch detection, and the top layer consists of floating electrodes for haptics, which couple with the bottom electrodes to turn the touch sensors into haptics actuators, explained LoPresti. “We drive the haptics with the same touch sensing lines, capacitively coupled through the glass to the top electrodes, closing the circuit. The glass provides galvanic isolation to it is very safe” the CEO continued. “We don’t complicate the touch panel very much, so the cost differential is negligible” LoPresti added, noting that Tanvas owns the IP (through multiple patents) on how the top electrodes must be patterned relative to the bottom electrodes to properly maximize the electroadhesion effects.

Another important part of the IP is the firmware and software necessary to deliver these haptic effects. The startup has developed a complete development kit with all the tools to design the haptics for any touch interface with ready to use widgets for scroll buttons, sliders or rotating knobs. It also offers to train design engineers with its haptics solution or to design bespoke haptics solutions.

“The tool itself is simple. A greyscale image of the UI graphics provides the haptics intent to our rendering engine, indicating what effect must be attributed to what pixel” explained LoPresti. Any image can be turned into a texture across 255 levels of friction, with pure white representing the highest friction and pure black the lowest friction”.

Visual image.

“We can change the haptic effects as fast as you refresh the image on display. You could feel the texture of sand, then rub it off the screen and feel a different texture underneath. We can layer the haptics too. For example a round button with clicks could have a different granularity level if you tap it once, or become a binary button (left or right click) upon a double tap” said the CEO.

Haptics greyscale image.

For now, the company’s demonstrators use off-the-shelf components, but in the future, Tanvas also wants to create a custom touch-display microcontroller integrating both the touch sensing and haptics functions, without having to synchronize two different components. And this would prove cost-competitive with any alternative touch and haptics solutions. The haptics are felt within a millisecond of touch detection.

The CEO also emphasized that this technology is completely solid-state, not only implemented without any moving parts, but also without having to vibrate the screen even through the use of piezoelectric actuators (also considered as solid-state technology compared to eccentric rotating mass motors).

This is an important distinction, LoPresti argued, because driving piezoelectric actuators at high frequencies to get the desired physical haptic effects through vibrations do come with some issues, namely buzzing noises and resonances which need to be dampened.

“In a car, if you want to use a vibrotactile solution, you have to engineer dampening hardware to attenuate unwanted vibrations, this adds cost and weight, so most OEMs try to avoid having to dampen their screen” he said.

“In our touch plus haptics solution, the touch panel is the coverlens, which makes the bill of materials compelling depending on the size and shape of the screen.”

LoPresti estimates that 10″ diagonal in size is where the inflexion point starts for TanvasTouch to become compelling on a cost basis, versus vibrotactile haptics solutions.

“The bigger the screen, the more complicated it is to damp, let alone across curved surfaces. We have demonstrated a 15″ display with Innolux, and because the technology is easily scalable, they will be able to combine multi-touch with haptics across their entire portfolio, including large curved displays. Because we are not vibrating the screen, we can deliver different haptics at different places of the screen”.

At CES 2020, the company announced a partnership with display manufacturer Innolux to produce a 15” automotive-qualified touch display using TanvasTouch, its programmable textures and haptic effects on smooth physical surfaces. The company has engaged with several OEMs in the automotive space, its first focus market, where it found the most traction.

“We have already shipped pre-production prototypes to automotive OEMs to evaluate surface haptics in future vehicles. This is the plan we are pursuing today, because car makers have literally come to us to solve driver distraction issues around cockpit displays, they want to reduce glances and minimize the time a driver has his/her eyes off the road”.

“There isn’t a very strong pull from the consumer space such as the mobile phone. We want the market to evolve a bit more so OEMs know what they really want to do with such haptics. By the time we reach production volumes for the automotive market, we’ll have a solution that fits better in form factor and cost wise for the consumer market. We are waiting for the market to catch up.”

One consumer application LoPresti sees tangible for TanvasTouch is a foldable laptop with a full screen instead of the keypad. The technology is also applicable to other surfaces made of plastic or metal including soft surfaces such as track pads. Because it is software-driven, it does not require any tuning. This means the textures and haptic effects can be harmonized across size, shape and surface. In a car, this could be across the cockpit display but also on door handles, the steering wheel and upholstery.

Tanvas has completed a series A funding round of $12 millions and it plans to raise an additional $20 millions in 2020.

Tanvas –

Related articles:

French startup promises meaningful haptics

2D to 3D conversion adds texture on top

Haptics to replace side buttons on smartphones

Augmented reality gets physical with haptics

KEMET to commoditize haptics

NXP backs Senseg’s electrostatic touch


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