Printable Tags Turn Everyday Objects into Smart Devices Engineers have developed printable metal tags （标签）that could be attached to everyday objects and turn them into smart Internet of Things devices．
The metal tags are made from copper foil （铜箔） printed onto thin， flexible， paper-like materials to reflect WiFi signals． The tags work essentially like "mirrors" that reflect radio signals from a WiFi router（路由器）． When a user's finger touches these "mirrors"， it disturbs the reflected WiFi signals in such a way that can be remotely sensed by a WiFi receiver like a smartphone．
The tags can be nailed onto objects that people touch every day， like water bottles， walls or doors． These objects then become smart and connected devices that can signal a WiFi device whenever a user interacts with them． The tags can also be shaped into thin keypads or smart home control panels that can be used to remotely operate WiFi-connected speakers and other Internet of Things devices．
Xinyu Zhang， a professor of electrical and computer engineering， named the technology LiveTag． He pictures people using LiveTag technology to track human interaction with everyday objects． For example， LiveTag could potentially be used to assess the recovery of patients who have suffered from stroke （中风）． "When patients return home， they could use this technology to provide data based on how they interact with everyday objects at home， whether they are opening or closing doors in a normal way， or if they are able to pick up bottles of water， for example． The amount， intensity and frequency of their activities could be recorded and sent to their doctors to evaluate their recovery，" said Zhang． "And this can all be done in the comfort of their own homes rather than having to keep going back to the clinic for frequent testing，" he added．
The researchers note several limitations of the technology． LiveTag currently cannot work with a WiFi receiver further than one meter away， so researchers are working on improving the tag sensitivity and detection range． Ultimately， the team aims to develop a way to make the tags using normal paper and ink printing， which would make them cheaper to mass produce．



When people touch a printable metal tag， ______ ．

A. they are actually touching a mirror
B. the WiFi router will stop sending signals
C. the reflected WiFi signals will be disturbed
D. their fingers can be sensed by a WiFi router

LiveTag can probably be used to ______ ．

A. precisely locate everyday objects
B. remotely control a WiFi-connected TV
C. easily block signals from WiFi devices
D. greatly improve one's physical condition

LiveTag helps stroke patients by ______ ．

A. evaluating the process of their recovery
B. sending data of their activities to doctors
C. connecting their smartphones with doctors"
D. recording doctors" assessments of their recovery