Microphone
German inventor Johann Philipp Reis designed an early sound transmitter that used a metallic strip attached to a vibrating membrane that would produce intermittent current. Better results were achieved with the "liquid transmitter" design in Scottish-American Alexander Graham Bell's telephone of 1876 – the diaphragm was attached to a conductive rod in an acid solution. These systems, however, gave a very poor sound quality.
The first microphone that enabled proper voice telephony was the (loose-contact) carbon microphone. This was independently developed by David Edward Hughes in England and Emile Berliner and Thomas Edison in the US. Although Edison was awarded the first patent (after a long legal dispute) 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. The carbon microphone is the direct prototype of today's microphones and was critical in the development of telephony, broadcasting and the recording industries. Thomas Edison refined the carbon microphone into his carbon-button transmitter of 1886. This microphone was employed at the first ever radio broadcast, a performance at the New York Metropolitan Opera House in 1910.
In 1916, E.C. Wente of Western Electric developed the next breakthrough with the first condenser microphone. In 1923, the first practical moving coil microphone was built. The Marconi-Sykes magnetophone, developed by Captain H. J. Round, became the standard for BBC studios in London. This was improved in 1930 by Alan Blumlein and Herbert Holman who released the HB1A and was the best standard of the day.
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.