Katharine Burr Blodgett (January 10, 1898 – October 12, 1979) was an American physicist and chemist known for her work on surface chemistry, in particular her invention of "invisible" or nonreflective glass while working at General Electric. She was the first woman to be awarded a PhD in physics from the University of Cambridge, in 1926.
Early life Blodgett was born on January 10, 1898, in Schenectady, New York. She was the second child of Katharine Buchanan (Burr) and George Reddington Blodgett. Her father was a patent attorney at General Electric where he headed that department. He was shot and killed in his home by a burglar just before she was born. GE offered a $5,000 reward for the arrest and conviction of the killer, but the suspected killer hanged himself in his jail cell in Salem, New York. Her mother was financially secure after her husband's death, and she moved to New York City with Katharine and her son George Jr. shortly after Katharine's birth. In 1901, Katharine's mother moved the family to France so that the children would be bilingual. They lived there for several years, returned to New York for a year, during which time Katharine attended school in Saranac Lake, then spent time traveling through Germany. In 1912, Blodgett returned to New York City with her family and attended New York City's Rayson School.
Education Blodgett's early childhood was split between New York and Europe, and she wasn't enrolled in school until she was eight years old. After attending Rayson School in New York City, she entered Bryn Mawr College on a scholarship, where she was inspired by two professors in particular: mathematician Charlotte Angas Scott and physicist James Barnes. In 1917, Irving Langmuir, a former colleague of her father and future Nobel laureate, took Katharine on a tour of General Electric (GE)'s research laboratories. He offered her a research position at GE if she first completed higher education, so she enrolled in a master's degree program at the University of Chicago after receiving her bachelor's degree. At the University of Chicago she studied gas adsorption with Harvey B. Lemon, researching the chemical structure of charcoals used in gas masks. She graduated in 1918 and took a research scientist position working with Langmuir. After six years at the company, Blodgett decided to pursue a doctoral degree with hopes of advancing further within GE. Langmuir arranged for her to study physics at the Cavendish Laboratory of Cambridge University, persuading somewhat reluctant administrators to offer one of their few positions to a woman. She was enrolled at Newnham College, matriculating in 1924. She studied with Sir Ernest Rutherford and in 1926 became the first woman to receive a PhD in physics from Cambridge University.
Work at General Electric Blodgett was hired by the General Electric company as a research scientist in 1918 after receiving a master's degree from the University of Chicago. She was the first woman to work as a scientist for General Electric Laboratory in Schenectady, NY. She often worked with Irving Langmuir, who had pioneered a technique for creating single-molecule thin films on the surface of water. Blodgett and Langmuir explored the application of similar techniques to lipids, polymers, and proteins, creating monomolecular coatings designed to cover surfaces of water, metal, or glass. These special coatings were oily and could be deposited in layers only a few nanometers thick. In 1935, Blodgett extended Langmuir's work by devising a method to spread multiple layers of a monomolecular coating, one layer at a time, onto glass or metal. By repeatedly dipping a metal plate into water covered by a layer of a long-chain fatty acid, she was able to stack layers onto the plate with molecular precision. The apparatus which she used and refined is known as the Langmuir–Blodgett trough. Blodgett used barium stearate to cover glass with 44 monomolecular layers, making the glass more than 99% transmissive and creating "invisible" glass. The visible light reflected by the layers of film canceled the reflections created by the glass. This type of coating is referred to as nonreflective or antireflective because very little light is reflected. While in principle, Blodgett's multilayer thin films had potential for use as antireflective coatings, General Electric never commercialized them because they were too soft and could easily be wiped off a surface. Other types of films employing harder antireflective coatings or etched surfaces proved more useful for applications such as camera lenses. Blodgett also invented a color gauge, a method to measure the thickness of molecular coatings on glass to the nearest one millionth of an inch. The gauge employed the concept that different thicknesses of coatings are different colors. While examining the layering of stearic acid on a glass plate, she realized that the addition of each layer, about 2/10,000,000 inch thick, reliably changed the color of the plate. Before her invention, the best measurement instruments were only accurate to a few thousandths of an inch. Her glass "ruler" much more precisely showed the progression of colors and their corresponding thicknesses. Measuring thickness became as simple as matching colors. The color gauge was marketed for a time by General Electric. Blodgett and Langmuir also worked on improvements to the light bulb. Their studies on electrical discharges in gases helped lay the foundations for plasma physics. Blodgett was issued eight U.S. patents during her career. She was the sole inventor on all but two of the patents, working with Vincent J. Schaefer as co-inventor. Blodgett published over 30 technical papers in various scientific journals. Her research also included the investigation of methods for deicing aircraft wings, and improving smokescreens during WWII.
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