1820 -- Hans Christian Ørsted discovered that an electrified wire deflected a nearby magnetic compass needle.

1823 -- Andre Marie Ampere coined the word solenoid for his coiled wire form that intensified the magnetic field.

1830s -- Joseph Henry refined the iron core solenoid, further strengthening its magnetic field.

1837 -- Charles Grafton Page heard galvanic music emanating from an iron bar near a coil. The music fleetingly appeared at the moment of contact or disconnection of a battery to the coil.

1841 -- James Prescott Joule determined that magnetic constriction, or "magnetostriction," of iron was too small to be a motor.

1912 -- After the Titanic struck an iceberg and sank, the loss of life strongly motivated the search for ways of using the new electromechanical/mechatronic technologies to detect submerged objects.

1917 -- Paul Langevin employed piezoelectric quartz sonar to detect submarines by acoustic echo.

Naturally, navies took a keen interest. Sonar transducers increased in power as the dominant electromechanical/mechatronic technology see-sawed between piezoelectric and magnetostrictive. By WWII, magnetostrictive nickel progressed while the war induced a shortage of mica for use as a capacitor dielectric. Enter barium titanate as a substitute; its piezoelectric properties were found to be better than quartz, soon followed by the lead zirconate / lead titanate (PZT) composition still in use.

1963 -- Searching for ever-greater power, the U.S. Navy began to investigate the properties of rare earths, culminating in an intermetallic alloy of terbium, dysprosium, and iron (elements 65, 66, and 26) known as terfenol-d. In an application that requires both speed and power, terfenol-d has the advantage of durability because the terbium atom is not completely round due to quantum mechanical effects. Its magnetostriction is natural and cannot be degraded or destroyed meaning that terfenol-d will survive being "pushed" very hard.

1998 -- To cut emissions, work began on fuel injector pilot valves driven by fast terfenol-d actuators. One design worked in a vehicle that was raced across southwest deserts and then driven to Michigan.

2001 -- It was predicted that speed would increase yet further with more compressive preload and fewer coil turns.

2004 -- Speed predictions incorporated into patent application.

2007 -- U.S. patent 7,255,290 issued.

2010 -- Speed predictions exceeded with three times expected expansion.

2012 -- Actuator ruggedized with hardened end caps on rod.

2013 -- Control method development started.

2015 -- OEM diesel fuel injector solenoid and servo valve replaced by terfenol-d actuator and hydraulic compensator. Engine test proved continuous control over needle. Very slight changes in electrical input yielded very slight changes in heat release.

2019 -- Multiple versions of control law proven on test hardware.