While electret microphones are losing some marketshare to microelectromechanical ones in things like airpods, they've played a huge part in now ubiquitous phone and acoustic technologies in the late 20th and early 21st centuries. When I was a postdoc I was fortunate one day to meet their coinventor, James West, who was still at Bell Labs, when (if I recall correctly) his summer student gave a presentation on some lead-free ultra-adhesive solder they were working on. He was still patenting inventions within the last two years, in his late 80s - impressive!
Monday, June 15, 2020
The foil electret microphone
Pivoting back toward science by way of technology.... Some very large fraction of the microphones out there in electronic gadgets are based on electrets. An electret is an insulating material with a locked-in electrical polarization - for example, take a molten or solvated polymer, embed highly polar molecules in there, and solidify in the presence of a large polarizing electric field. The electrical polarization means that there is an effective surface charge density. You can make that electret into a free-standing foil or a film coating a backing to make a diaphragm. When that film vibrates, it will generate an oscillating voltage on a nearby electrode (which could, say, be the gate electrode of a field-effect transistor). Voila - a microphone that is simple, readily manufacturable, and doesn't need an external power supply.
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6 comments:
Jim West is still doing well as far as I can tell. I was fortunate to serve with him on a committee last year and it was interesting getting a chance to talk with him. He's quite an inspirational figure.
Dear Prof,
A post on Rashbha effect would be nice and how is the effect of importance in spintronics or even vallyetronics for 2D materials.
Looks like the Trump administration is going all-in on destroying the future of US scientific and technological progress. Our university may have problems keeping a very, very talented group of postdocs and students if no one is able to stop these visa restrictions.
Well, in one way, he is forcing other countries to develop and use their own highly skilled labour which is going to be a boost for them. Let Americans work for the USA and other's for their countries, otherwise, it is one country that dominates.
Don't agree with that, this talent will simply move onto the next scientifically developed country that will let them in. The only loser in this situation is the US. China, Germany, Canada, etc. will all benefit because of their comparatively more welcoming policies for scientists.
@Anon 1:37, Welcoming policies are there but if there are no jobs, then the talent is going to stay at home. Don't think there will be a sudden boom in the job market.
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