How a Chinese company’s pressure sensors spell end of physical smartphone buttons

South China Morning Post 發布於 2019年11月19日16:11 • Ben Sin
  • Physical buttons could be replaced by highly sensitive pressure sensors made by Shenzhen tech company NDT
  • The sensors can detect 1,000 levels of pressure and sit under the phone’s screen or body
Haptic pressure sensors embedded in smartphones could do away with the need for physical buttons. A Chinese company founded by a former Motorola engineer is a leading developer of the technology. Photo: Ben Sin

A consistent trend in personal computing is the removal of moving hardware parts.

The computer mouse used to rely on an internal rubber ball to track movement; now it's all done via lasers. Video game consoles and desktop computers once were turned on by a physical moving power switch; now it's usually a capacitive touch panel. And it's been more than a decade since Steve Jobs ushered in the modern era of smartphones that replaced a physical keyboard with a touch screen one.

For smartphones " the industry that now leads the way in computing innovation " next to go will be physical buttons.

The change began around 2016, when many Android phones moved to digital on-screen navigation buttons and Apple replaced the iPhone's clickable circular home button with a tactile one on the iPhone 7. But those were relatively simple solutions that left user interaction the same " press an area to trigger an action.

The small black rectangles on the chip are the

A more advanced solution is beginning to roll out in newer handsets: any part of a phone can be pressed, and instead of just offering on/off functionality, these parts are pressure sensitive, essentially serving as analogue force sensors.

This tech is already in used on Google's three most recent Pixel phones, in which the left and right side of the chassis can be squeezed to launch Google Assistant. Chinese smartphone brand Vivo's Nex 3 flagship handset allowed users to adjust volume by pressing into the side bezel; and the company's gaming-centric iQoo phones can turn its aluminium chassis into analogue shoulder buttons for gaming. Chinese smartphone maker Xiaomi's upcoming Mix Alpha will have no physical buttons at all " users power on the device by pressing into the side of the device, which is entirely covered by an OLED display.

The paper-thin pressure sensors are made in batches in a single sheet. Photo: Ben Sin

All the aforementioned phones use technology from New Degree Technology, a mid-sized company based in Shenzhen, southern China, that specialises in building paper-thin, flexible sensors that can be embedded underneath a metal, glass, or plastic surface " basically any part of a smartphone.

These sensors can detect over 1,000 levels of pressure: the difference between a very light tap or a hard press, and everything in between.

The company's founder, Hao Li, worked as an engineer at Motorola in the United States from 2001 to 2010. It was during his time working on display panels that he envisioned sensors that can detect varying degrees of pressure.

Hao Li, founder of New Degree Technology, worked at Motorola in the US for nearly a decade before moving back to China to start his company. Photo: Ben Sin

"At the time, I didn't know what we would use such functionality for, but I just knew that it would enhance user interaction and experience with a UI," says Li, 47, who has a PhD in material science from the University of Maryland.

Li left Motorola in 2011 to move back to China and founded New Degree Technology, which he prefers to call NDT.

Consumers today may recall that iPhone models released from 2015 to 2018 did, in fact, offer a display panel that can detect a normal tap and a harder press " Apple calls the tech "3D Touch" " but NDT actually beat Apple to market: the ZTE Axon Mini used NDT's sensors three months ahead of the iPhone 6S.

The Vivo Nex 3 doesn't have traditional power or volume buttons, instead users press the side of the phone. Photo: Ben Sin

Apple's 3D Touch sensors " which the company scrapped beginning with this year's iPhone 11 series " were also less sophisticated, able to detect only two levels of pressure, while NDT's sensors offer full analogue sensitivity.

The magic behind NDT's tech comes from the tiny resistors in the sensors that detect "deformation" pressure from the outside surface. Once the deformation has been registered, the resistors measure the pressure and output a voltage proportional to the amount of force that has been applied. In other words, it is turning physical analogue force into digital information for a device's brain to calculate and determine action.

It was a long road for NDT to go from small start-up needing to prove its tech to now being a major part of Google's "idealised" version of an Android device.

New Degree Technology engineers demonstrate the process of attaching the sensor. It's as simple as applying a sticker. Photo: Ben Sin

The company's first major client was ZTE, which made use of the sensors in the aforementioned Axon Mini. A year later Google began using NDT's sensors in its Pixel phones, starting with the Pixel 2. The partnership had been years in the brewing, and dates back to another US tech giant.

"In 2013 we were at CES (Consumer Electronics Show in Las Vegas) where our sensors won the Innovation Award," recalls Li. "And engineers from Amazon noticed us. They were working on the Amazon Kindle Voyage at the time and thought our force sensor tech would work well on the e-reader.

"Users would be able to press on the Kindle Voyage's screen to turn a page " the harder the press, the more pages turn at once."

Physical buttons may go the way of hardware keyboards on phones. Photo: Ben Sin

The partnership never materialised, because the key technical person working on the Kindle Voyage was let go by Amazon. According to Li, he moved to Google to work on the Pixel, where he recommended NDT to the tech giant.

The company's sensors are also used in other consumer products, such as an e-cigarette (vape) pen with a pressure-sensitive switch to control vapour output, but Li says the bulk of the company's business is from smartphones " he says the company is on pace to generate 200 million yuan (US$28.5 million) in revenue this year.

But Li is hoping to expand his company's portfolio. He says there are many practical use cases for NDT's sensors: lift doors, or inside car tyres to detect air pressure. He demonstrated a pulse detection kit using just a small metal nub with NDT's sensors inside.

In 2013 we were at the Consumer Electronics Show in Las Vegas, where our sensors won the Innovation Award. And engineers from Amazon noticed us.Hao Li, founder of NDT

Considering how much smartphone brands are pushing their vision of a sleek, all-screen device with no buttons, ports or bumps, there is likely to be more demand for force sensors to replace traditional buttons.

Huawei's recent Mate 30 Pro uses similar tech (although from an undisclosed vendor); and Samsung is rumoured to be working on a buttonless Galaxy phone for the future.

Apple is still considered the trendsetter in the smartphone world. The company's engineers considered an iPhone with no physical buttons before deciding the technology wasn't ready.

Perhaps by 2020 or 2021, the tech will mature enough for Apple's liking. And once Apple does something, there will be no going back " physical buttons will be dead.

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