New device enables battery-free computer input at the tip of your finger

Friday, November 29, 2019

Researchers at the David R. Cheriton Cheriton School of Computer Science have created a device for wearable computer input suitable for many situations, just by touching your fingertips together in different ways.

Called Tip-Tap, the device is inexpensive and battery-free because it uses radio frequency identification (RFID) tags to sense when fingertips touch. The device could be added to disposable surgical gloves, allowing surgeons to access preoperative planning diagrams in an operating room. 

photo of RFID-based tip-tap technology attached to hand

The RFID-based Tip-Tap device attached to a person’s hand as an on-skin electronic tattoo. 

Each contact array has three RFID chips connected to a copper tape half-antenna shaped like half of an RFID tag. Tip-Tap is designed to sense when two fingers are touching, allowing someone to control a finger while doing something else.

“One of the many possible applications of the device is in surgeries. What typically happens now with operation digital preplanning is that an assistant is responsible for navigating the computer and communicating with the surgeon, but this is slow and difficult,” said Daniel Vogel, a professor in Waterloo’s David R. Cheriton School of Computer Science. “If the surgeon tries to navigate it themselves using a touchscreen or a mouse, it’s problematic because it would require constant sterilization, and current alternatives such as big gestures tracked by computer vision can get very tiring.

photo of Ju Wang, Omid Abari, Daniel Vogel and Keiko Katsuragawa

Clockwise from bottom left: Postdoctoral fellow Ju Wang, Professors Omid Abari, Daniel Vogel and Keiko Katsuragawa.

Professor Katsuragawa demonstrates the RFID Tip-Tap device on a glove with smooth pads. When pressing the thumb and index contacts together two RFID chips are connected in series and two flexible core wires work as a single dipole antenna. The radio signal from the tags is received by the white reader behind Professor Vogel.

“The idea is if you mount Tip-Tap in surgical gloves, surgeons could navigate the computer themselves from where they are, and it won’t affect their other actions like picking up the scalpel.”

Researchers created the prototype of Tip-Tap as part of a new partnership with the National Research Council of Canada. 

In developing the method, the researchers mapped the most comfortable areas on the index finger for people to touch with their thumb, and tested different designs for the input points, such as smooth, bumps or magnets. Following user tests with an early wired prototype to benchmark performance, they tackled the problem of making it battery-free.

The researchers were able to make Tip-Tap battery-free by splitting the antenna of an RFID tag in two, and equipping each side with three chips to enable two-dimensions of fingertip input, the first time this had ever been done.

The new RFID tag can be integrated into a glove or attached directly on the skin as a temporary tattoo.

“We used this design in two prototype Tip-Tap devices — a glove with a range of four metres and an on-skin tattoo,” said Professor Vogel. “Such devices are useful for issuing simple commands when a user cannot easily hold an input device, and the usage context is a defined area — for example, factory workers, surgeons, or people exercising in a gym.

“This is the only device of its kind that we’re aware of that doesn’t require a battery or cumbersome wires to make it work.”

This research in the news

The study, Tip-Tap: Battery-free Discrete 2D Fingertip Input, was conducted by Keiko Katsuragawa, Ju Wang, Ziyang Shan, Ningshan Ouyang, Omid Abari and Daniel Vogel from the Cheriton School of Compute Science. Keiko Katsuragawa is also a research officer at the National Research Council.

The study was presented recently at UIST 2019, the 32nd ACM User Interface Software and Technology Symposium in New Orleans, Louisiana. The ACM Symposium on User Interface Software and Technology (UIST) is the premier forum for innovations in human-computer interfaces. 

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