In 1907, Marshall A. Barber, a professor of bacteriology at the University of Kansas, first described a mechanical pipette holder. This small micromanipulator, which clamped directly to the microscope stage, could manoeuver a glass pipette along three dimensions using a screw mechanism. The pipette holder incorporated other significant contributions that Barber had made technology of micromanipulation. He had earlier described the moist chamber, a glass enclosure placed on the microscope stage that kept the sample fresh during the process of micromanipulation and positioned the sample between the microscope objective and the microtool.
Barber’s micropipette holder emerged from an earlier method for isolating microorganisms that Barber had described in 1904. This involved a moist chamber made of glass, lined with moistened filter paper, and roofed with a large cover glass. The sample to be manipulated was suspended in a droplet hanging from the cover glass. This solved a key problem: before the moist chamber and hanging droplet, the tool had been placed between the microscope objective and the specimen so that only lower power objectives with longer focal lengths could be used. The chamber also provided a moist environment that kept organic specimens alive or fresh over longer periods.
1904, Barber had not yet presented a mechanical pipette holder. Instead he used a handheld pipette, drawn out to a fine tip. He mentionedat the time that “I have experimented with mechanical contrivances intended to replace the hand, but have not found them necessary. No great difficulty is met with in acquiring sufficient skill to use the method.” (Barber 1904, 493).
By 1907, when he first introduced his mechanical pipette holder, Barber had either changed his mind or arrived at workable solution. The pipette holder incorporated several mechanical “movements” based on a screw that pushed a carriage along a bearing surface. The combined movement of these three screw-actuated carriages maneuvered the pipette in three dimensions.
At first, Barber used his pipette holder only for isolating microorganisms. Barber claimed.
I have successfully isolated single spores of fungi, single cells of algae, various yeasts, and many bacteria, including Streptococcus, from pus. I have little difficulty in obtaining colonies of amoebae or infusoria grown from single individuals… It seems probable by this method of isolation something may be done in the way of isolating organisms which are with difficulty handled by ordinary methods. [Barber 1907, 47]
While Barber first suggested that the instrument could be used for microdissection in 1911, it was first used for this purpose by G. L. Kite at the Marine Biological Laboratory in Woods Hole Massachusetts to investigate the fertilization membrane of the egg of the sea urchin. [Chambers 1918, 123] In 1911, Barber, also described a complicated apparatus for microinjection.Published illustrations depict an instrument that did not change substantially over its period of active use. In, 1908, Barber mentioned “a modified pipette holder constructed to hold two pipettes”. These could be adjusted independently of the other and permitted the operator to make two isolations before changing pipettes. He preferred the simplicity of the single version, however. [Barber 1908, p. 382.]
Barber credited “Mr. Montrose Burrows, who assisted much in designing the pipette holder described above.” [Barber 1907, 47] Several generations of the instrument were made at the University of Kansas and sold to researchers worldwide. The double holder model of the instrument was also manufactured by Fowler Shops a the University of Texas. [Chambers 1918, 125, 127] A major revision, shown below, was introduced by F. Hecker of Kansas City in 1916.
Hecker’s update introduced a number of improvements to eliminate the wear that quickly led to mechanical inaccuracy in the original mechanism. It was made of cast bronze rather than brass, with the milled parts machined separately fastened to the instrument by screws. Among other improvements, new adjusting set screws were added to compensate for wear in the bearing surface while the bearing surfaces were replaced by 5 thin brass shims each 1/1000th of an inch thick. When one became warn, it was removed and the carriage retightened using the set screws. [Hecker 1916, 306-307]
Such improvements, which added considerable complexity, show the challenge of improving an instrument whose mechanism was fundamentally limited and which was being applied to ever more precise work. At the Marine Biological Laboratory in Woods Hole, Massachusetts, for instance, Robert Chambers and G. L. Kite had been using the instrument to investigate the structures of the cell and the process of fertilization since 2012. In 1918, Chambers described his own improved version of the pipette holder.Within four years of describing his modifications of Barber’s instrument, Chambers created a new micromanipulator that incorporated many of Barber’s innovations—the first commercially successful micromanipulator. He claimed that his own instrument, which was based on a hinge/ spring mechanism, solved certain fundamental flaws in Barber’s pipette holder. He noted that Barber’s instrument “unless skillfully made, has too much lost motion, and wear and tear soon renders the movement jerky and undependable.” [Chambers 1922a, 334] Later, other instruments were introduced which were also based on the rack and pinion mechanism. They addressed the problems of lost motion and backlash that had limited Barber’s instrument.