Microflown makes one, it uses very small temperature differences. You can look for acoustic particle velocity sensor to find more about how they work. I can't r

Microflown makes one, it uses very small temperature differences. You can look for acoustic particle velocity sensor to find more about how they work. I can't remember the paper, otherwise I'd provide a better link. https://www.microflown.com/products/standard-probes https://www.microflown.com/products/standard-probes This PDF may be helpful http://past.isma-isaac.be/downloads/isma2010/papers/isma2010_0607.pdf http://past.isma-isaac.be/downloads/isma2010/papers/isma2010...