Biomedical Engineering Reference
In-Depth Information
description offered by Capitanio et al. (2005), a custom structure made of ErGaAl (erbium, gallium,
aluminum) alloy can be used to build an optical microscope with high mechanical stability. In detail,
the mechanical structure is composed by three 250 × 250 × 30 mm
3
platforms held by four stainless-
steel columns with 25 mm diameter, 500 mm height (see Figure 2.1).
The lower platform serves as a basis for the whole microscope. The middle platform serves as a basis
for the sample stage. Two manual translators, allowing gross movements of the sample in the XY plane,
and a piezoelectric translator, allowing fine movements, can be mechanically coupled to the middle
platform. The objective lens is positioned along the optical axis by means of two orthogonal ErGaAl
brackets fixed to the same platform. The higher platform serves as a basis for the detection system and
the support structure of the collection optics. The condenser lens is mounted on a support which can
be translated vertically to allow mounting and removal of the sample. The microscope was mounted
with an inverted geometry aimed at being used in molecular and cell biology imaging application. Both
upright and inverted geometry can be realized starting from a custom mechanical body. In general,
inverted or upright geometry is chosen according to the samples to be imaged: upright geometry is in
general more comfortable for imaging thick massive samples, while inverted geometry is more indicated
for imaging thin samples.
A schematic drawing of the experimental apparatus, mounted with inverted geometry, is depicted
in a 3D rendering in Figure 2.1. This solution offers the great advantage of being relatively inexpen-
sive (about few thousands of euros) and completely customizable according to the requirements of the
experiment, but it also has some drawbacks. In particular, commercial microscopes offer a better com-
fort for the user and do not require any alignment procedure. Moreover, the technical complexity of
such a project and the time consumed in designing, realizing, and mounting the instrument could
FIgurE 2.1
A 3D-rendering of a custom mechanical structure in ErGaAl alloy used to build an optical micro-
scope. The platform at the bottom serves as a basis for the microscope, the middle platform sustains the objec-
tive and the microscope slide support. The upper platform hosts the condenser and the detection system. (From
Capitanio, M., Cicchi, R. and Pavone, F. S. 2005.
Eur. Phys. J. B,
46: 1-8. Reprinted with kind permission of
European
Physical Journal
B
(EPJ).)
