= Microtome
{wiki}
A <microtome> is an instrument for <microtomy>: a supported specimen and a knife move relative to one another to separate a thin physical section. The apparatus combines a specimen holder, a knife holder, a cutting motion and a controlled feed that presents new material for the next cut. An <ultramicrotome> is specialized for very thin sections, including sections for <transmission electron microscopy>.
A concrete materials-research installation at Yale uses a Leica Ultra UC7, with a trimming mill and glass knife maker. Its listed specimen materials include <polymers>, <material fibres> and soft metals.<Microtome at the Yale Institute for Nanoscience and Quantum Engineering>[About the instrument, accessories and materials list]{ref} For the thin-section cutting cycle, JEOL describes advancing the specimen by a preset feed and moving it against a <diamond knife>.<Ultramicrotomy by JEOL>[Glossary, specimen advance and downward cutting stroke]{ref} The supports must hold the specimen and knife securely enough that commanded motion is meaningfully related to the material removed.
An original ideal feed-drive calculation illustrates the distinction between mechanism and outcome. Suppose a hypothetical drive advances a <lead screw> by pitch $p$ per revolution, has reduction ratio $G$ motor revolutions per screw revolution, and receives $N$ equally spaced command steps per motor revolution. Its nominal advance per step is
$$
\delta=\frac{p}{GN}.
$$
For chosen $p=0.50\,\mathrm{mm}$, $G=100$ and $N=200$, this gives $\delta=25\,\mathrm{nm}$. Four steps command a <nominal section feed> of $100\,\mathrm{nm}$. This is an illustrative mechanism, not a claim about the UC7's internal drive. Motor motion does not independently establish the <physical section thickness>: <backlash>, elastic motion, <thermal expansion> and <section compression> can intervene.
A bounded apparatus experiment would cut a stable <polymer> reference at several feed settings, measure the recovered <physical section thickness> independently, and retain the cutting order and operating conditions. Agreement of motor counts with the command tests the drive readout; agreement of measured sections with the intended thickness tests more of the complete process. The distinction parallels the need for an independent readout when testing <positioning repeatability>.
Back to article page
