Carbon microphone
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone (then called transmitter). This was independently developed around 1878 by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent in mid-1877, Hughes had demonstrated his working device in front of many witnesses some years earlier, and most historians credit him with its invention.
Probe tip
The discovery of a sharp probe tip has always been of significant interest among the researchers considering its importance in the material, life and biological sciences for mapping the surface structure and material properties at molecular or atomic dimension. The history of tip can be tracked long back in nineteenth century during the invention of Phonautograph in 1859. Phonautograph is the predecessor of modern gramophone. It was invented by Scott and Koenig. It consisted of a parchment diaphragm with an attached stylus (sort of a pen-holder), along with a Hog’s hair, which was used to trace a wavy line on a lamp-blacked surface [Musical mirror by Bryceson, Richard, Jan. 1929-Dec.1930]. In the later development gramophone came out where along with other replacements, the Hog’s hair was replaced by a needle to reproduce sound [Musical mirror by Bryceson, Richard, Jan. 1929-Dec.1930]. In 1940, a pantograph was built utilizing a shielded probe and adjustable tip. A stylus was free to slide vertically to be in contact with the paper. In 1948, a tip was employed in probe circuit to measure peak voltage. The fabrication of electrochemically etched sharp tungsten, copper, nickel and molybdenum tip was reported by Muller in 1937. The revolution for sharp tips occurred in producing a good and various kind of tip with different shape, size, aspect ratio composed of tungsten wire, silicon, diamond, Carbon nanotube etc. occurred with Si-based circuit technologies. This allowed tips for numerous applications in the broad spectrum of nanotechnological fields. Following STM invention came Atomic force microscopy (AFM) by Gerd Binnig, Calvin F. Quate, and Christoph Gerber in 1986. In their instrument they used diamond broken piece as tip sticking it to a hand-cut gold foil cantilever. Focused ion and electron beam technique for the fabrication of strong, stable, reproducible SiN pyramidal tip with 1.0 μm length and 0.1 μm diameter was reported by Russell in 1992. Ground breaking advancement came through the introduction of microfabrication methods for the fabrication of precised conical or pyramidal silicon and silicon nitride tip. Later, numerous research experiments were explored to fabricate comparatively less expensive and robust tungsten tip production and characterization technique to attain less than 50 nm radius of curvature.