1931:
- Cyclotron: A particle accelerator invented by Ernest Lawrence that uses a strong magnetic field to accelerate charged particles in a circular path.
- Electric razor: Alexander Horowitz introduced the first electric shaver.
1932:
- Scanning Electron Microscope (SEM): Developed by Max Knoll and Ernst Ruska, the SEM uses a focused beam of electrons to create an image of a sample's surface.
- Nuclear chain reaction: James Chadwick discovered the neutron, a fundamental subatomic particle.
- Television system: Vladimir Zworykin developed an electronic television system using a cathode ray tube.
- Instant camera: Edwin Land introduced the first instant camera, the Land Camera, which could produce finished photographs within minutes.
1933:
- FM Radio: Edwin Howard Armstrong developed Frequency Modulation (FM) radio, which provided higher-fidelity sound transmission compared to AM radio.
1934:
- Automatic transmission: General Motors introduced the first mass-produced automobile with an automatic transmission, the Oldsmobile Automatic Safety Transmission.
1935:
- Nylon: Wallace Carothers and his team at DuPont developed nylon, the first synthetic fiber.
1936:
- Xerography: Chester Carlson invented xerography, a dry copying process that would later lead to the development of photocopiers.
- Radar: Robert Watson-Watt developed the first practical radar system for detecting aircraft.
1937:
- Helicopter: Igor Sikorsky designed and built the VS-300, the first successful single-rotor helicopter.
1938:
- Ballpoint pen: László Bíró patented the ballpoint pen, a writing instrument that used a small ball to regulate ink flow.
- Photocopier: Chester Carlson and Otto Kornei produced the first permanent photocopy using the xerographic process.
1939:
- Jet engine: Frank Whittle successfully tested the first turbojet engine, which would revolutionize aviation.
- Television broadcasting: The first public television broadcast took place at the 1939 New York World's Fair.
1940:
- Polystyrene: Hermann Staudinger discovered the structure of polystyrene, a lightweight and versatile plastic material.
- Electron microscope: Ernst Ruska developed the first transmission electron microscope, allowing for the detailed examination of materials at the atomic level.