Caroline Eichler

Margarethe Caroline Eichler (born in 1808 or 1809; died 6 September 1843 in Berlin) was a German inventor, instrument maker and prostheses designer. She was the first woman in Prussia to receive a patent (for her leg prosthesis) and was also the inventor of the first practical modern hand prosthesis.

Biography Caroline Eichler was born in 1808 or 1809, presumably in Nordhausen or Berlin, as the third daughter of painter Johann Gottlieb Eichler. In those days, young women were usually denied higher education opportunities or apprenticeships, and although no documentation has been found describing her schooling, her work demonstrates a knowledge of physics and technical mechanics. Around 1826 Eichler was working as a nanny and later worked as a nurse. Earlier designs either had no knee joint or, like the artificial legs described by the surgeon Ambroise Paré in the 16th century, had to be operated by pulling a cord.

Eichler's construction consisted of a tinplate, brass (and later nickel silver sheet) shaft for the leg's stump, a hollow lower leg made of linden, willow or poplar wood glued over with canvas, and a foot with two parts, which were also made of wood, all attached to the jointed leg piece.

Eichler favorably compared the amputee's effort required to walk with her prosthesis to that of a toddler learning to walk or someone learning to dance. She said crutches were not necessary with her design as only a walking stick was required, and after a training period of one to two weeks, one would be able to walk on paved and unpaved floors and even climb stairs without using even a stick.

Eichler's hand prosthesis, like the Baliff's, was operated by the remaining muscles in the upper arm stump using a pulling mechanism, but her mechanism differed significantly from his. The fingers were actively closed and stretched again by means of coil springs made of nickel silver wire, one in each finger joint. Gut strings with a diameter of about 1 mm were used for power transmission.

Structurally, the fingers featured three movable joints and the thumb had two joints. Digits could also be moved individually using five separate sliders on the wrist, but only passively. In contrast to the iron hands of Renaissance times, the prosthesis had an opposable thumb that enabled a forceps grip with a sixth slider.

First usable body-powered artificial hand, developed by Caroline Eichler, patented in 1836.Eichler's model also adopted design features from the Iron Hand: the wrist could bend at the wrist and a radial bearing made it possible to passively rotate the hand in relation to the forearm shaft (pronation or supination).

The hand prosthesis was formed from nickel silver sheet modeled after two plaster casts (one from the stump of the arm and one from the healthy hand) and weighed only about . The phalanxes were covered with cork on the inside to improve the grip. The wearer of the prosthesis would have been able to write, sew and embroider with it, and also be able to lift loads of up to . The hand could easily be dismantled into its individual parts to simplify repairs and keep costs down, but the purchase price was quite high at 75 to 100 thalers. The nickel silver used by Eichler remained the standard material for hand prostheses into the 20th century.