Sensing Tags

Interactive everyday things are essential for ubiquitous sensing and interaction. Replace existing things with battery-powered ‘smart’ things is not sustainable, since the large amount of batteries would introduce huge maintenance efforts and cause significant damage to the environment. So, I develop maintenance and battery free wireless sensing tags that can be easily deployed on existing everyday things. The sensor’s many hardware components (e.g. power source, RF oscillator) and functions (e.g. signal digitalization) are offloaded to a remote resource-abundant computer. The cost, size, and power consumption of such sensors are then minimized, which makes them suitable for ubiquitous deployment on existing infrastructure and objects.

Figure 1. BitID sensors can be easily made (a), registered (b), and deployed (c) on a door to detect intrusion (d).

In BitID, I propose to modify commercial-off-the-shelf (COTS) low-cost and passive UHF RFID tags to detect binary object states. By attaching shorting stubs to exposed antenna around the chip, the tag’s readability is modulated by the connection status of the shorting stubs. Users can easily make BitID sensors using everyday tools like copper tape and scissors. We deploy BitID sensors on six objects in a room to show its high scalability. The codes for the BitID sensing system is open sourced on GitHub. The RFID reader used in BitID can be expensive and is not widely available yet. So I look into opportunities to leverage more accessible computers (e.g. smart phone, smart ring) to power and compute for the resource-constrained sensors. In FlexTouch, conductive tapes are attached to the touch screen of a smart phone to enable large-scale sensing (e.g. Yoga mat for posture detection). In ThermalRing, I used a smart ring with a low-power thermal camera to recognize passive aluminum stickers for quick access.

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Tengxiang ZHANG
Assistant Research Scientist

I use my hardware and software skills to build interfaces between the physical and digital world.