S1: 3D Printing the Components of the OPN Scope

S1: 3D Printing the Components of the OPN Scope
S1: 3D Printing the Components of the OPN Scope
Chris Stewart and John Giannini *
St. Olaf College, Biology Department, 1520 St. Olaf Avenue, Northfield, MN 55057
* Email: giannini@stolaf.edu
We describe here how to 3D print the various parts for the OPN Scope and OPN
Drawer. We designed each of these components using the free version of DesignSpark
Mechanical (RS Components, Ltd., Corby, Northamptonshire, UK), which is available at
http://www.rs-online.com/designspark/electronics/eng/page/mechanical under the
“Download DesignSpark Mechanical” heading. We have also included both the CAD
and STL files for each part as Supporting Information (S2 and S3, respectively), so that
readers can print or modify them as needed. In addition, we provide the general print
dimensions and volumes for these parts in Table S1-1, so that readers can determine
whether their 3D printers can accommodate the size of the components or whether
other printing arrangements should be made.
Table S1-1. Approximate Print Dimensions (l x w x h) and
Volumes (Build, Support) for Parts of the OPN Scope and
OPN Drawer
Dimensions (cm)
Volumes (cm3)
OPN Scope
Outer Shell
11.00 x 5.55 x 8.50
173.70, 20.20
7.20 x 4.40 x 4.50
58.05, 6.10
Drawer Handle
0.95 x 0.95 x 8.30
5.25, 0.20
Light Tube
4.35 x 4.35 x 6.65
25.10, 1.50
Eyepiece Tube
3.30 x 3.30 x 5.70
19.85, 3.85
Mount Adapter
4.40 x 4.40 x 2.45
12.45, 1.65
7.20 x 4.40 x 4.50
44.75, 6.10
Drawer Handle
0.95 x 0.95 x 8.30
5.25, 0.20
Ex. Filter
3.95 x 3.30 x 0.70
6.10, 0.70
Mirror (Rect.)
4.85 x 3.30 x 0.40
3.85, 0.85
Mirror (Circ.)
4.85 x 3.30 x 0.40
4.15, 0.85
Em. Filter
4.20 x 4.35 x 0.65
7.85, 1.95
OPN Drawer
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We designed the outer shell of the OPN Scope (S2A, S3A) to be big enough to hold a
drawer for an Olympus BX2-style fluorescence filter cube – one of the larger versions on
the market (Fig. S1-1A, far left). The five OPN Scope drawers that we have designed to
date (S2B01 – S2B05, S3B01 – S3B05) all have the same external dimensions and use
the same handle (S2C, S3C). Thus, only the internal dimensions of the drawers need to
change to accommodate a given filter cube (Fig. S1-1B). At present, we have designed
drawers to hold the following types of cubes: Olympus BX2 (S2B01, S3B01), Zeiss Axio
(S2B02, S3B02), Leitz/Leica Astroplan (S2B03, S3B03), Nikon Diaphot/TMD-style
(S2B04, S3B04); and Leitz/Leica DMIRB (S2B05, S3B05) models (Figure S1-1A from left
to right).
Figure S1-1. Examples of fluorescence filter cubes that will fit in the OPN Scope along with their corresponding drawers.
With respect to the other components of the OPN Scope, we designed the tube for
the light source (S2D, S3D) to hold an Outlite WT03 tactical LED flashlight, which has a
cylindrical head (and, thus, can easily slide into a circular tube). We further included a
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4.75-mm diameter hole at one end of the tube, so that a 10-24 thumbscrew could be
threaded through the opening to stabilize the flashlight.
We designed the tube for the eyepiece (S2E01, S3E02) to hold one from an Olympus
CH-style microscope and the mounting adapter (S2F01, S3F01) to fit the same. We
chose this microscope initially because it is used in several teaching labs at our school
and generally costs between $350 (used) and $900 (new) online. We, however, have
also designed eyepieces and mounting adapters to fit other compound microscopes,
such as Nikon AlphaPhot-2 YSR, Nikon Eclipse E300, Zeiss AxioStar Plus, and Zeiss
PrimoStar models (S2E02 – S2E05 and S3E02 – S3E05, S2F02 – S2F05 and S3F02 –
S3F05, respectively) since these instruments are also used at our school.
Readers, however, can modify the CAD files for these components (or design their
own) to create parts that would fit other compound light microscopes and their
eyepieces. In so doing, however, please take care to maintain the proper tube length
between the eyepiece and objective lens. Also, please know that some microscopes do
not have removable eyepieces, such as the Nikon and Zeiss models described above.
Nevertheless, in these instances, we have found that using an eyepiece from another
microscope can suffice. For example, even though Olympus, Nikon, and Zeiss appear to
have different tube lengths for their microscopes, we were able to bring images into
focus between low (40x) and high (400x) magnification using an eyepiece from an
Olympus CH-2 microscope placed in either its own tube (S2E01, S3E01) or the specific
eyepiece tube for each Nikon or Zeiss model described above. Alternatively, readers
can use a digital microscope camera in place of an eyepiece, and there are several
inexpensive models on the market (although cameras with more MegaPixels will
typically generate higher-quality images).
For the OPN Drawer (S2G, S3G), which also requires a handle (S2H, S3H), we
removed large portions of the side walls, so that the dichroic mirror holder could easily
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be slid into place (Fig. S1-2). We also created a chamber in the front of the drawer to
hold the excitation filter, and we reduced the diameter of the hole in the front face to 15
mm to keep this filter in place. While readers can modify this dimension, we found no
need to do so during our tests.
Figure S1-2. The OPN Drawer along with its holders for an excitation
filter (left), dichroic mirror (middle), and emission filter (right).
The holders for the excitation and emission filters (S2I and S3I, S2L and S3L) can
contain circular filters as big as 25-mm in diameter and 5-mm thick. The holders for
the dichroic mirror can contain rectangular mirrors as big as 38 mm x 26 mm (l x w)
and 1.0-mm thick (S2J, S3J) or circular mirrors with a maximum diameter of 25 mm
and thickness of 1.0 mm (S2K, S3K). We chose these dimensions because they
appeared to be the largest ones used in filter sets made by several prominent
manufacturers. To 3D print components for smaller parts, readers need only change
the corresponding internal dimensions in the supporting CAD files by using the “Pull”
function in the free version of DesignSpark Mechanical.
STL Files and Test Prints
When generating the STL files for the OPN Scope and OPN Drawer in DesignSpark
Mechanical (Export Options >> 3D Print (*.STL) >> Options), we found that setting the
“resolution” to “custom” with a deviation of 0.05 mm and an angle of 0.1 degrees helped
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to generate smooth curves in the resulting part. For even finer resolution, readers can
enter values for the “facet maximum edge length” and “facet maximum aspect ratio,”
although these options create much larger STL files (some over 100 MB given the size of
the components, which can end up crashing the program). Also, because different 3D
printers may have different error tolerances, we recommend printing out a few test
pieces first (e.g., a portion of a tube or part of the outer shell) to ensure that the above
settings will generate the desired shapes and dimensions. These test prints should also
indicate whether any dimensions in the CAD files need to be changed to accommodate a
specific part.
3D Printing
We originally printed the parts for the OPN Scope and OPN Drawer on a Mojo 3D
printer using QuickPacks of Black ABS build material and soluble support material
(Stratasys, Ltd., Eden Prairie, MN). After a part had finished printing, we placed it in a
WaveWash55 Support Cleaning System (Stratasys, Ltd., Eden Prairie, MN) until all of
the support material had dissolved. We then rinsed each part in warm water and dried
them before using them to assemble the OPN Scope. However, because the
WaveWash55 solution is rather hot and has a pH of around 10, please read the Hazards
section below before using the WaveWash55 system to clean any parts.
Of course, readers could use other 3D printers or filament instead. For example, we
recently purchased a FlashForge Creator Pro 3D Printer (FlashForge USA, Rowland
Heights, CA) and have successfully printed parts for the OPN Scope and OPN Drawer
with 1.75-mm diameter SainSmart Black ABS Filament using MakerBot Desktop
software and the Simplify3D slicing program.
Also, for those who do not have direct access to a 3D printer, there are websites,
where STL files can be uploaded, printed, and shipped to you for a fee (which is usually
based on the number of parts printed, the amount of filament used, and the shipping
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costs involved). For example, in March 2016, we uploaded the STL files for the various
components of the OPN Scope to www.3dprintingpricecheck.com, which estimated that
it would cost between roughly $85 and $136 to print these parts in ABS plastic (high
resolution) or strong and flexible black plastic, depending on the type of drawer involved
using either the MakeXYZ or Shapeways printing websites (not including any taxes
and/or shipping). Similarly, www.3dprintingpricecheck.com estimated that it would
cost around $37 to print the components for an OPN Drawer that fit one filter set using
MakeXYZ or Shapeways (again, not including any taxes or shipping). Thus, printing
these parts along with the basic components of the OPN Scope should cost between
$100 and $144 in total. For an exact quote, however, readers should upload their
desired STL files to their preferred 3D printing website.
As explained above, the solution used in the WaveWash55 Support Cleaning System
is an alkaline one (pH 10), which is made by adding an Ecoworks tablet to an empty
WaveWash55 container and then gently adding 7.5 liters (2 gallons) of warm tap water
(away from the tablet) to avoid any splashes. Because the tablet itself as well as the
subsequent solution can cause serious skin and eye irritation upon contact, please
review both the WaveWash55 user guide and the Material Data Safety Sheet for the
Ecoworks tablets before making or using the solution. Also, please wear the proper
protective equipment (e.g., gloves, goggles, and a lab coat or heavy clothes) when
preparing or working with the solution (we further use a pair of salad tongs to remove
parts from the WaveWash55 container since the solution itself often becomes rather
hot). Finally, please make sure to dispose of any used WaveWash solution properly
since it is an alkaline mixture, which further contains dissolved support material (i.e.,
plastic). For example, we pour our used WaveWash fluid into large, shallow baking
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pans and let the liquid evaporate over several days until only a malleable plastic
remains, which we then scrape off and dispose of as waste.
Fluorescence Filter Cubes and Sets
In our OPN Scopes, we typically employ used fluorescence filter cubes, which can be
purchased on eBay or other suitable marketplaces for used laboratory equipment (often
for between $125 and $500 if buying a single-band cube, depending on the make and
model). For example, the used cubes pictured in Figure S1-1A cost between $125 and
$480 on eBay.
We further tested the OPN Drawer with the filters and dichroic mirror from a used
Zeiss Axio series DAPI/FITC/Texas-Red cube that we purchased on eBay for $150 (Fig.
S1-1A, second left). The excitation and emission filters measured 25 mm in diameter
with thicknesses of 5.0 and 3.5 mm, respectively. The dichroic mirror measured 36 mm
x 30 mm (l x w) with a thickness of approximately 1 mm. We then modified the internal
dimensions of the three OPN Drawer holders to fit these parts and 3D printed them as
described above.
The Light Source
After testing several different light sources, we found that tactical LED flashlights
with a maximum brightness of 2,000 lumens (as well as a convex lens and adjustable
head for focusing the beam) tended to generate the clearest and brightest fluorescent
images. However, other LED flashlights may suffice. Three models that performed well
during our tests were the Outlite A100, the Outlite WT03, and the Coast G20 inspection
light (Fig. S1-3).
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Figure S1-3. LED flashlights that we use with the OPN Scope: an
Outlite A100 (left), an Outlite WT03 (middle), and a Coast G20 (right).
As our main light source, we use an Outlite WT03 tactical LED flashlight, which we
purchased on Amazon for roughly $13 (Fig. S1-3, middle). We chose this model
because it has three brightness settings (with a maximum of 2,000 lumens), a convex
lens that enables the beam to be intensely focused, and a cylindrical head, so that the
flashlight can easily fit into a 3D-printed circular tube.
Although the Outlite A100 (Fig. S1-3, left) also works well, this flashlight has a large
ellipsoidal head, which does not easily fit into a cylindrical tube. Nevertheless, we have
found that the beam from this flashlight can be shown directly into the hole leading to
the excitation filter to induce fluorescence without the light tube needing to be present.
In these instances, we typically use a ring stand and clamp to hold the flashlight in
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We have also found that the Coast G20 inspection LED light (Fig. S1-3, right) can
excite fluorescence in cells stained with Rhodamine B or Acridine Orange, although a
more powerful light (e.g., a 2,000-lumens model) was needed to induce fluorescence in
cells tagged with a fluorescent protein. Given its much smaller diameter, however, the
Coast G20 light requires two cylindrical adapters (S2M, S3M) to fit into the larger light
tube for the Outlite WT03 flashlight. Alternatively, readers can print a version of the
OPN Scope that was designed only to hold the Coast G20 inspection light (S2N, S3N
and S2O, S3O), which thus has a much smaller light tube. We include the general
print dimensions and volumes for these three different components in Table S1-2.
Table S1-2. Approximate Print Dimensions (l x w x h) and
Volumes (Build, Support) for Parts Fitting the Coast G20
Inspection Light
Adapters for Coast G20
(for Outlite WT03 tube)
Dimensions (cm)
7.65 x 7.65 x 1.55
Volumes (cm3)
26.25, 10.20
Outer Shell – Coast G20
11.55 x 5.55 x 8.50
172.10, 21.50
Light Tube – Coast G20
2.70 x 2.70 x 7.50
17.70, 8.40
Using the same March 2016 estimates from www.3dprintingpricecheck.com,
printing the adapters for the Coast G20 inspection light would add between $6 and $12
to the prior printing costs on either MakeXYZ or Shapeways. Alternatively, printing the
various components for the Coast G20 version of the OPN Scope (with just one drawer)
would cost between $84 and $131, using either the MakeXYZ or Shapeways websites
(not including any taxes or shipping costs).
Finally, given our experiences in testing and refining the OPN Scope and OPN
Drawer, we provide some helpful hints for their use.
Helpful Hints for the OPN Scope
First, we use compression fittings when assembling the various parts of our OPN
Scopes, which is why each hole was designed to be larger than its corresponding tube.
While readers are free to alter these dimensions to ensure a tighter fit, we prefer to wrap
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a few layers of electrical tape around the end of a tube to achieve the same result,
especially in light of the variations in 3D printing error tolerances discussed earlier.
Second, when viewing fluorescent images, a flashlight may at times be too dim (or
too bright) to obtain useful fluorescence. In these instances, readers can try using
newer (or older) batteries, adjusting the position or angle of the light in the tube,
changing the brightness setting, or adjusting the focus of the flashlight (assuming that
it has these last two options). Alternatively, if using a fluorescent stain or dye, readers
may want to try increasing (or diluting) its strength.
Third, some LED flashlights (especially those that lack a convex lens to focus the
beam) can create a dark “halo” in the image or may light up only part of the field of
view, and this latter effect can even occur with the Outlite WT03 when its head is not
fully extended. In these instances, images can appear framed in darkness when viewed
through the eyepiece or on a video screen. Similarly, part of a fluorescent cell can
appear cut off if it happens to cross the edge of the halo or beam. If this occurs, it may
be possible to correct for the effect by changing the position of the slide slightly or
adjusting the position of the flashlight. However, using a flashlight with a convex lens
that is fully extended should avoid this issue.
Fourth, if left on for prolonged periods of time in the light tube, the Outlite WT03
that we used became rather warm. As a result, consider turning off the light when it is
not in use, which should also reduce the amount of fluorescent bleaching (i.e., the
fading of a specimen) that can occur when it is bathed in excitation light for long
Helpful Hints for the OPN Drawer
First, for those who are unfamiliar with the components of a fluorescence filter set,
each piece should be marked in some way to indicate which direction the part should
face. For example, the band around the excitation filter typically has an arrow on it,
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pointing in the direction that the filter should face. Similarly, the band around the
emission filter often has a dot or some other mark on it, indicating which side should
face up. Likewise, the dichroic mirror frequently has a special coating on the side that
should face the excitation light source. Readers should keep these markings in mind
when placing the components of filter set into their respective holders and then into the
OPN Drawer.
Second, if using the free version of DesignSpark Mechanical to change the
dimensions of a holder to fit a particular filter or mirror, we recommend first changing
the distances between the bottom “lips” that hold a part in place and then changing the
distances between the “walls” that surround the edges of the filter or mirror. Otherwise,
the part must be rotated in more complicated ways in DesignSpark Mechanical to
access each side.
Third, some emission filters perform best when tilted at a slight angle in their filter
cube (e.g., by 1º to 5º). If necessary, readers can achieve this result in DesignSpark
Mechanical by selecting bottom “lip” that holds the emission filter in place, clicking on
the “Move” button, and then rotating the structure by the desired angle.
Fourth, because the various components of a filter set, especially the dichroic
mirror, are quite fragile, please exercise great care when handling them. As a result,
instructors may want to assemble the parts of an OPN Drawer themselves, so that the
filters and/or mirror are not accidentally scratched or broken.
Fifth, relatedly, we recommend having a dedicated OPN Drawer (or at least a
dedicated set of holders) for each filter set. Not only does this approach make changing
sets much easier, it further reduces the chances of damaging a filter or mirror by
repeatedly moving it into and out of a holder or drawer.
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