Two clever ideas from Tech Review

Posted April 19, 2005

I've recently been flipping through back issues of MIT's Tech Review magazine, since I got out of the habit of reading it a while ago but still have stacks of them piled up. A couple of blurbs caught my eye as being "clever ideas": something you can describe in a sentence or two but that isn't really obvious until some genius thinks it up for the first time. I distinguish these from generic patentable ideas in that how to do them is usually straightforward, but what you should do at all is the special part.

Solar cells unfortunately waste a lot of the sunlight that falls on them, partially because the material each type of cell is made from is only sensitive to a portion of the spectrum: light in other color bands is just wasted. These guys thought up a clever way around this problem. You get a bunch of different types of cells, put reflective filters in front of each one that screens out all the light except the part they can each use, and then mount them all together on the inside of a mirrored sphere. Light enters the sphere and then just keeps bouncing around and around until it finds and gets absorbed by whichever solar cell can make use of it. Clever.

A theme that has been running through the wearables group at the Media Lab for a while is the context-sensitive cellphone. Why isn't my phone smart enough to recognize that I'm in a movie theater and that it should switch to vibrate mode? Or see that I'm riding a bike and it shouldn't ring at all... unless it's a family member calling, maybe. Mitsubishi's Cambridge lab thought that it would be neat if your phone could tell when you move it away from your ear (to switch sides, attend to something else, look something up, etc.) and automatically start recording any conversation you miss. When it detects you're listening again, it plays it back at accelerated speed — taking out pauses and so forth — until you catch up. Cellphones already have enough capabilities to do this, except for the mere matter of some extra software and a face-proximity sensor that you could implement with a five-cent infrared part. Clever.

By a strange coincidence, it seems that the cellphone research was done by the same folks who wrote a very clever paper on how to use LEDs as sensors and communication links: even though LEDs are primarily output devices, they also are sensitive to light, so you can use them as detectors in the proper circuit configurations. I need to try this sometime...