I used to drive a station wagon and one of its best features, especially useful in winter, was the rear window windshield wipers. They were so useful that I wondered why they were standard equipment only on wagons and hatchbacks and came to the conclusion that this must be because those rear windows were pretty much flat, while the curved and the sloping rear windshields of other cars made it technologically difficult. I am not sure if that is the real reason since it seems like engineers could have overcome that.
I now read that new technology may overcome that problem and do away with the need for mechanical wipers entirely. The racing car company McLaren is developing a system, based on those used on some aircraft that don’t use mechanical wipers but instead use a transducer at the corner of the windscreen that causes ultrasound vibrations that deflects water and mud and bugs.
If that technology can be transferred economically to cars, and it seems likely that it can and will, then there is no reason that we could not have them on rear windows too. And we won’t have that annoying problem of wipers freezing to the glass to deal with.
This article gives origin of the current wipers.
Windscreen wipers were invented in by the American property developer Mary Anderson who received a patent for her window cleaning device in 1903.
The invention came about during a trip to New York City. It was raining heavily and Mrs Anderson noticed that drivers had to open the windows of their cars in order to see out of them.
She wanted to find a solution and invented a swinging arm device with a rubber blade that was operated by the driver from within the vehicle using a lever.
At first the invention was highly critiqued as many claimed that the device would actually distract drivers, but by 1916 windscreen wipers had become standard on most vehicles.