A
Diseases spread in many ways. An infected person can cough or sneeze on someone nearby, or they can spread germs through a handshake. But sometimes we pick up germs indirectly. A sick person might leave behind bacteria or viruses when they touch a door handle, for example. But what if those surfaces could clean themselves?
Two teenagers from Hong Kong asked themselves the same question. Now they’ve developed a door handle that can kill germs on contact.
The idea is simple. Every time the door is opened, the movement creates power that starts a germ-killing reaction on the handle. In lab tests, their system killed about 99.8 percent of the germs that they spread onto lab dishes covered with their material.
Research by others has shown that door handles in public areas are often home to lots of bacteria and viruses, notes 17-year-old Sum Ming (“Simon”）Wong. He and his schoolmate Kin Pong (Michael) Li, 18, wanted to design a covering for door handles that would kill germs.
After doing some research, they learned that a mineral called titanium dioxide (二氧化钛）is known to kill bacteria. It’s already used in many products, from paints to desserts. To make their covering, the teenagers made the mineral into a very fine powder.
Titanium dioxide kills bacteria best when lit by ultraviolet (紫外线的) light, says Simon. UV light is found in sunlight. But UV light does not naturally shine on indoor handles or any used at night, so the teenagers light their door handle from within.
To make sure the light reaches the coated surface, the teenagers made their door handle out of clear glass. Each end fits into a bracket (托架). Inside one of the brackets is a strong light-emitting diode (LED). From it comes UV light.
And here’s the interesting part: The power that makes the UV light shine comes from opening and closing the door. The power from the door is then carried by wire to the LED inside the door handle.
The door handle system, Michael and Simon say, might cost no more than about $13 (about 81 yuan) to build.
21. The ways diseases spread are mentioned at the beginning of the text to .
A. demonstrate how most diseases are spread indirectly
B. remind readers of the importance of cleaning their hands
C. explain how to kill bacteria or viruses effectively
D. help to describe a new invention that prevents diseases from spreading
22. The LED is placed inside the brackets to .
A. supply enough power to the handle system
B. produce titanium dioxide to kill bacteria
C. provide UV light to help titanium dioxide work better
D. direct the UV light in sunlight to the coated surface
23. What is the author’s attitude toward Michael and Simon’s door handle system?
A. Cautious B. Critical C. Disappointed D. Enthusiastic
