S4: Building a PVC Version of the OPN Scope...For the tubes that hold the optics and flashlight in...

Journal of Chemical Education 5/5/16 Page 1 of 19

S4: Building a PVC Version of the OPN Scope

Chris Stewart and John Giannini *

St. Olaf College, Biology Department, 1520 St. Olaf Avenue, Northfield, MN 55057

* Email: [email protected]

We describe here how to build a version of the OPN Scope, using parts available at most

hardware stores (e.g., wood or PVC board, PVC tubing and couplings, screws, electrical tape,

etc.) or online (e.g., used optics and fluorescence filter cubes). We further include a list of the

key materials needed to build this microscope (along with their estimated cost) in Table S4-1.

Readers, however, should note that some of these items (specifically, the PVC board, PVC pipe,

and wooden dowel) will make more than one OPN Scope. We also provide all dimensions below

in lumber units (i.e., inches) since those are the standard units of measurement for these types

of materials and their related tools.

Table S4-1. Description and Approximate Cost of the Parts

Needed to Build the PVC Version of the OPN Scope

Part Approx. Cost

¾-inch thick wood or PVC board (8 in. wide x 8 ft. long) $5 to $30

¾-inch PVC pipe (Schedule 40; 5 ft. long) $2

¾-inch PVC coupling (Schedule 40) for eyepiece $1

1 x ¾ inch PVC bushing (Schedule 80) for objective lens $2

Female 3-inch PVC DWV female adapter (Schedule 40) $3

Male 3-inch PVC DWV male adapter (Schedule 40) $3

Push-button LED light $1 to $15

LED flashlight $10 to $25

Twenty (20) drywall screws (#6; course; 1¼ inches long) $2

Wooden dowel with a ½-inch diameter $1

Scotch “extreme” fasteners or similar connectors $3

Roll of electrical tape $1 to $3

AA and AAA batteries (one four-pack of each) $4

Microscope optics (ocular and object lenses) $15 to $50

Fluorescence filter cube $125 to $450

Total $178 to $594

While readers can use wood to make many of the components for this microscope, we

recommend using PVC board since it is more rigid than many woods and also should not warp,

split, or rot over time. In addition, although this microscope can be built using hand tools, it

can be assembled more quickly using power tools (e.g., a chop or table saw, a portable drill or

mailto:[email protected]


drill press, a disk or belt sander, etc.), which should be available at most high schools, colleges,

or universities. For those unfamiliar with such tools, however, please review the Hazards

section below as the associated dangers are significant.

The Optics, Fluorescence Filter Cubes, and Light Sources

Because the optics and filter cube are typically the most important (and often the most

expensive) components of any fluorescence microscope, we discuss them first. We obtained

our optics (a 10x eyepiece, and 4x, 10x, and 40x objectives) by purchasing a used Carlsan

microscope on eBay for roughly $15 (Figure S4-1A). Alternatively, readers can purchase new

or used optics at other suitable online or other marketplaces for laboratory equipment or

salvage them from older or broken microscopes.

Figure S4-1. Used optics (A) and filter cubes (B) for the PVC version of the OPN Scope.

We bought our filter cubes (Leitz N2.1 and I3 models) on eBay as well (Figure S4-1B).

These cubes allow for viewing in the red (N2.1) and green (I3) emission spectra, and they cost

roughly $175 and $125, respectively. For our light sources, we used a Coast G20 inspection


light ($11) and a Rite Lite Hi-Output push-button LED accent light ($13) that we purchased at

a regional hardware chain. Other LED flashlights and light sources, however, will suffice.

The Microscope Stand (Base, Support Arm, and Platform)

We used ¾-inch thick PVC board (8 inches wide x 8 feet long) to build the microscope

stand, which consists of a 6¼-inch x 6¼-inch square base, a 7½-inch tall support arm made

from pieces that are 3¼ and 2½ inches wide, and an upper platform that resembles the shape

of home plate on a baseball diamond (Fig. S4-2A). The square part of this platform (Fig. S4-2A,

top left) measures 4½ inches x 4½ inches, and the corresponding isosceles triangle has an

altitude of roughly 2¼ inches and side length of approximately 3¼ inches. We further drilled a

1⅛-inch hole approximately ¼ inch below the center of the square, so that the light tube for

the microscope can fit through it. We used eight #6 drywall screws (course-threaded and 1¼

inches long) to hold the four pieces of the stand together, which allows for easy assembly and

dismantling if need be (Fig. S4-2B). We also placed four felt pads near the bottom corners of

the base, so that the stand will sit flat on a table or benchtop.

Figure S4-2. The unassembled (A) and assembled (B) pieces of the PVC microscope stand.


The Adjustable Microscope Stage

We made the adjustable microscope stage from a 3-inch diameter PVC DWV coupling,

cutting approximately 1¾ inches off the “top” of the male fitting and drilling a 1½-inch hole in

the side of the female fitting, so that students can easily access the push-button LED (Fig. S4-

3A). Alternatively, readers can leave the male PVC coupling intact and add 1¾ inches to the

pieces of the support arm. For the stage itself, we cut a 3½-inch diameter circular disk out of

PVC board and drilled a ½-inch diameter hole in the center to provide a path for the light from

the push-button LED located below. We then sanded down the outside of the circular disk

slightly, so that it would fit into the PVC coupling. We further cut a 3½-inch diameter circle

from a large plastic weigh boat to serve as a condenser/diffuser, trimming its edge until it fit

into the PVC coupling. Other opaque materials, however, could be used for the diffuser

instead. Also, depending on the size of the push-button LED, readers can place the light on

another circular PVC disk, so that the light source will stay centered as the stage moves (Figs.

S4-3E and S4-3F).

Because the adjustable stage is made from a threaded PVC coupling, students can bring a

slide into focus simply by twisting the top coupling clockwise or counterclockwise while holding

the bottom coupling in place. Although this method does rotate the specimen in the field of

view, this usually does not present a problem at lower magnifications. Nevertheless, because a

sample can be rotated out of the field of view at higher magnifications (e.g., 400x), we provide a

design to stabilize the slide near the conclusion of this paper.


Figure S4-3. The adjustable microscope stage for the PVC version of the OPN Scope. (A) Standard 3-inch PVC DWV coupling and the modifications that we made to it. (B - D) Assembling the adjustable stage from its underlying parts. (E and F) Placing a smaller push-button LED light on a PVC disk, so that the light can move with the stage.

The Outer Shell that Holds the Fluorescence Filter Cube

To construct the outer shell that holds the fluorescence filter cube, we again used ¾-inch

thick PVC board and cut pieces that fit around the dimensions of our filter cubes (Fig. S4-4).

For the used Leitz N2.1 filter cube described above, which was approximately 1.50 inches x

1.15 inches x 1.35 inches (39 mm x 30 mm x 35 mm) in size, the PVC shell consisted of (i) a


front and a back piece, both measuring 2¾ inches x 3 inches, (ii) a top and a bottom piece,

both measuring 2¾ inches x 3½ inches, and (iii) two side pieces, both measuring 3½ inches x

1½ inches. Of course, because other types of filter cubes would have different dimensions,

readers would need to adjust the dimensions of these pieces accordingly (e.g., we made a

similar PVC shell for our used Leitz/Leica I3 filter cube only with slightly smaller dimensions

given the smaller size of that cube).

Figure S4-4. The PVC shell that holds the fluorescence filter cube. (A and B) The outer and inner sides of the shell. (C and D) Partially- and fully-assembled versions of the shell, showing how the filter cube fits into place.

In addition, as shown in Figure S4-4, we painted the inner sides of these pieces with flat

black spray paint to reduce the effects of glare inside the shell, and we held the six pieces of

the outer shell together with twelve #6 drywall screws that were course-threaded and 1¼-inch

long.


To hold the tubes for the ocular and objective lenses, we drilled 1⅛-inch diameter holes in

the top and bottom pieces roughly 1 inch away from the left edge along the center line. To hold

the tube for the flashlight, we drilled a 1⅛-inch diameter hole in the front piece slightly below

the center of the front face. The proper placing of this hole, however, will depend on the

specific filter cube used. We further drilled a ½-inch diameter hole in the back piece, so that a

wooden dowel could be used to slide the filter cube into and out of position for fluorescence

and bright-field viewing (Figs. S4-4C and S4-5). We then placed Scotch “Extreme” Fasteners

on one end of the dowel and on the back of the filter cube to hold the two together (Fig. S4-5B

and S4-5C). However, some cubes (e.g., Nikon Diaphot/TMD models) have an open back,

which may not allow for this type of attachment, and other cubes may have different

dimensions or designs, which might require the use of a different dowel.

Figure S4-5. Attaching a wooden dowel to the filter cube into to slide it in and out of place.


The Tubes that Hold the Optics and Flashlight

For the tubes that hold the optics and flashlight in place, we used ¾-inch Schedule 40 PVC

pipe, which has an outer diameter of roughly 1.05 inches. We further used a standard

Schedule 80 PVC SPG x SOC bushing (gray) to hold the objective lens in place and a Schedule

40 PVC socket coupling (white) to hold the eyepiece in place (Fig. S4-6).

Figure S4-6. The PVC tubes and fittings for the light source, objective lens, and eyepiece (from left to right, respectively).

As described below, we chose the lengths of the tubes for the lenses to ensure a 160-mm

distance between the ocular and objective lenses (the focal length for our used optics) given the

overall height of the PVC shell. However, since other lenses may have different focal lengths,

readers might need to use different tube lengths. In addition, given the focal lengths of some

lenses and the dimensions of some cubes, it is possible that readers may need to use a thinner

material for the outer shell (since ¾-inch thick PVC board may create too large a distance

between the optics to allow for proper focusing).


Given our used Carlsan optics, we cut the tube for the eyepiece (Fig. S4-7) to be roughly 1⅜

inches long, which was sufficient to hold the PVC coupling for the eyepiece in place. We also

wrapped one end of the PVC tube with electrical tape, so that it would fit snugly into the hole

on the top of the PVC shell.

Figure S4-7. The PVC tube and coupling that hold the eyepiece (wrapped with electrical tape for a tight fit).

Similarly, we cut the tube for the objective lens (Fig. S4-8) to be approximately 2 inches

long, which was needed to maintain the 160-mm distance between the ocular and objective

lenses when this tube was inserted into the bottom hole of the PVC shell. We also wrapped

that end of the PVC tube with several layers of electrical tape as well to ensure a tight fit

between the pieces.

Figure S4-8. The PVC tube and bushing that hold the objective lens (wrapped with electrical tape for a tight fit).

For the tube that holds the excitation light source (here, a Coast G20 flashlight), we used a

piece of PVC pipe that was 3½ inches long (Fig. S4-9). We have found that this length can

keep the light in place without it “drooping” too much over time due to the effects of gravity.


We also wrapped the Coast G20 light with several layers of electrical tape in two different

places, so that it would fit more smoothly into the PVC tube (Fig. S4-9C).

Figure S4-9. The PVC tube (A and B) for the LED flashlight (C).

As described above, for simplicity, we use compression fittings to secure each tube place,

wrapping one end with a few layers of electrical or PVC tape to ensure a tight fit. Alternatively,

readers could tap each hole and thread the outside of each PVC pipe to screw them into place

(although this approach would be more expensive and require more skill given the tools needed

for the job). While readers could also use PVC tape and PVC cement or epoxy to hold these

pieces in place permanently, we do not recommend this approach since it is often convenient to

disassemble the items for storage.

Also, once assembled, we put small amounts of LocTite fun-tak or Scotch mounting putty

on the bottom of the PVC shell to hold it in place on top of the microscope stand (Fig. S4-10).

However, readers can use other materials or methods to accomplish this task. Also, if using a

larger LED flashlight (such as the Outlite A100 or WT03 models), readers can remove the PVC

tube and use a ring stand and clamp to hold the light up to the hole for the excitation filter

directly (Fig. S4-10B).


Figure S4-10. The PVC version of the OPN Scope using different LED flashlights as an excitation light source. (A) Coast G20 in a ¾-inch PVC tube. (B) Outlite A100 held in place with a standard ring stand and clamp.

The Adapter for Mounting the Outer PVC Shell on a Conventional Compound Microscope

Given its modular design, the outer PVC shell of this microscope can be removed from its

stand and mounted onto a conventional compound microscope with a removable head (like the

3D-printed version of the OPN Scope). The mounting adapter for an Olympus CH-style

microscope consists of a ¾-inch long piece of ¾-inch PVC tubing, two SAE flat washers that fit

a ¾-inch screw (they have a 1½-inch outer diameter, 13/16-inch inner diameter, and are 9/64

inches thick), and a ½-inch long piece of ½-inch PVC tubing (Fig. S4-11A). However, other

microscopes may have different locking mechanisms. As a result, readers may need to use

different washers or other materials (likely with different dimensions) for their adapter.


Figure S4-11. An adapter for mounting the PVC shell onto an Olympus CH-style microscope. (A) The parts for the adapter. (B and C) The assembled adapter. (D) The adapter placed on an Olympus CH microscope with its head removed. (E) The PVC shell mounted on an Olympus CH microscope.

We beveled the edge of one of the washers using a grinder (Fig. S4-11A, right washer) so

that the adapter could be held in place by the thumbscrew on the Olympus microscope (Fig.

S4-11D). We further held all of the parts together using quick-drying epoxy. As with the other

PVC tubes, we wrapped a few layers of electrical tape around the ¾-inch PVC tube to ensure a

tight fit with the PVC shell (Fig. S4-11C).

Potential Issues or Challenges

Although the PVC version of the OPN Scope generally works quite well, we did encounter

some issues when building and testing the instrument, which we describe below.

First, it is very important to properly align the holes for the flashlight, filter cube, and

lenses. Thus, when cutting the pieces for the outer shell, readers should take care to properly


place the holes for these tubes given the ultimate location of the filter cube. For example, if the

flashlight is not properly aligned with excitation filter, then students will likely see fluorescence

only in part of the field of view (Fig. S4-12B). Although this issue is particularly pronounced at

lower magnifications (e.g., 40x or 100x), it can occur at higher magnifications as well (Fig. S4-

12D). While adjusting the position of the flashlight in the tube (or the tube itself) can often

resolve all or part of this issue, in our view, the proper alignment of the PVC tube and the filter

cube on the front end (i.e., during assembly) provides the best way to avoid this problem.

Figure S4-12. Effects of misaligned flashlight and filter cube. (A and B) Cells stained with Acridine Orange and viewed with a Leitz/Leica I3 cube at 100x total magnification. (C and D) Cells stained with Rhodamine B and viewed with a Leitz/Leica N2.1 cube at 400x total magnification.

In addition, the microscope is sensitive to vibrations, particularly at 400x total

magnification (even when felt pads, cork pads, or rubber mats are placed under the base as a

shock absorber). As a result, students should use a steady hand when moving the stage or


adjusting the focus in order to keep a specific specimen in the field of view, and this technique

will likely require some practice. Moreover, because focusing the microscope requires rotating

a circular stage, it is possible to move a specimen out of the field of view (especially at 400x

magnification). We, however, have designed ways to stabilize the slide platform during focusing

and to finely adjust the position of the stage in the X-Y direction, which we describe below.

Holding the Slide Platform in Place to Prevent a Specimen from Rotating Out of the Field of View

To prevent a slide from rotating as the PVC coupling is turned to bring an image into focus,

we used supplies that should be available at most high schools, colleges, or universities.

Specifically, we inverted a large (3¾-inch diameter) glass petri dish and held it in place using

lengths of glass pipettes that were glued to the side of the PVC coupling (Fig. S4-13). We

further glued small lengths of a plastic straw to the sides of the petri dish, so that it could

move up and down along the glass rods as the PVC coupling was rotated. We also glued

rectangular pieces of rubber matting on the sides of the coupling to provide enough clearance,

so that the new stage could smoothly move up and down.

Figure S4-13. Modifying the PVC stage, so that a slide will stay fixed on the platform as the coupling is rotated.


Because the petri dish added approximately 1⅝ inches to the height of the stage, we

had to remove this amount from the PVC coupling to maintain the distance between the

objective lens and the slide platform. Ultimately, we found that taking 1⅛ inch off the top of

the male coupling and ½ inch off the bottom of the female coupling worked well. However,

given the changes to the male coupling, we also needed to sand down the edge of the circular

PVC disk some more, so that it would fit in the modified piece. We further include a list of the

materials that we used for these modifications in Table S4-2 below. Of course, readers could

use other supplies instead.

Table S4-2. Parts Needed to Modify the PVC Stage to

Prevent Slides from Rotating on the Platform

Part (with Dimensions)

Large glass or plastic petri dish (3¾-inch diameter)

Two lengths of glass pipettes (¼-inch diameter, 4½ inches long)

Two lengths from a plastic straw (¼-inch diameter; 1½ inches long)

Two pieces of rubber matting (top; ½ inch x 1 ½ inches)

Two pieces of rubber matting (bottom; 1¼ inches x 1½ inches)

One 3-inch male PVC DWV coupling (3/4 inches remaining on fixture)

One 3-inch female PVC DWV couple (2½ inches remaining on fixture)

One PVC or wooden disk (3/4 inches think and 3⅜-inch diameter)

One hot glue gun with additional glue sticks (or epoxy)

Allowing for Fine Adjustments in the X-Y Position of the Microscope Stage

Although students can use their hands to move the PVC stage under the objective lens, at

high magnification (i.e., 400x), this technique requires a gentle touch to keep a specimen in the

field of view. As a result, we have also designed a microscope stand that allows for finer

movements in the X-Y position of the stage using parts available at most hardware stores (Fig.

S4-14). While we made the prototype depicted in Figure S4-14 using wood and lauan plywood,

readers should consider using PVC board and thin polycarbonate or acrylic sheets instead

since those materials should not warp, split, or rot over time.


Figure S4-14. A microscope stand that allows for fine adjustments in the X-Y position of the stage.

Specifically, the stand consists of an 8-inch x 10½-inch base that is ¾ inches thick, an 8-

inch tall support arm made from a “2 x 4,” and a 3½-inch x 6½-inch platform that is also ¾

inches thick and on which the PVC shell for the OPN Scope rests (Fig. S-14A). We further cut a

¾-inch by 2¾-inch notch out of this platform, so that the tube for the objective lens could fit

through this gap, and we held these pieces together using five #6 drywall screws that were

course threaded and 1¼ inches long.

To make the assembly for fine adjustments in the x-direction of the microscope stage, we

first glued a 3.4-inch diameter circular disk onto a 4-inch x 4½-inch piece of lauan plywood

that was 0.2 inches thick, so that the PVC coupling would fit snugly on top (Fig. S4-14B).

Then, for guide rails, we used a table saw to cut notches along two 5½-inch x 1⅛-inch runners


that were ¾ inches thick. We next anchored these guide rails onto a 5½-inch x 6½-inch base,

which was ¾ inches thick, using six drywall screws (Fig. S4-14C). Then, we slid the platform

into place, adjusting the screws as needed to ensure that the platform moved smoothly to the

right and left.

For the “control knob” that allows for fine adjustments in the x-direction, we first cut down

a ¼-inch fully-threaded tap bolt that was 1½ inches long, so that it was roughly ⅜ inches long.

We next placed the bolt through the hole in one half of a 2-inch x ⅝-inch “L” bracket, which we

had cut down using a hacksaw, and then through a standard ¼-inch washer (Figs. S4-14B

and S4-14D). We next used a single drywall screw to hold that bracket in place. Then, we

placed quick-drying epoxy on the far end of the bolt and treaded it into a ¼-inch rod coupling

nut that we had cut in half (Fig. S-14D). After the epoxy dried so that the bolt would stay fixed

in place, we ran another ¼-inch fully-threaded tap bolt that was 1 inch long into the opposite

end of the coupling nut and glued part of a Scotch “Extreme” Fastener to the head of that bolt.

Finally, we glued another Scotch “Extreme” Fastener to the side of the PVC coupling and

connected the two ends, so that the stage would move to the right or left when the coupling nut

was twisted (Fig. S-14D).

To allow for fine adjustments in the y-direction, we employed a similar approach. First, we

glued the above assembly onto a 5¾-inch x 6¼-inch piece of lauan plywood, which was 0.2

inches thick. Then, for these guide rails, we again used a table saw to cut notches along two

6½-inch x 1⅛-inch runners that were ¾ inches thick. We next anchored these guide rails onto

the base for the microscope stand using six drywall screws (Fig. S4-14A). We then slid the

above assembly into place and attached a similar “control knob” to the base (using a drywall

screw) to allow for fine adjustments in the y-direction of the stage (Fig. S4-14D).

Finally, we include a list of the specific parts needed to build this microscope stand (along

with some suggested dimensions) in Table S4-3 below. Readers, however, can adjust these

dimensions to fit their specific needs (e.g., while we cut down the ¼-inch tap bolts and

coupling nut so that they would fit within the overall dimensions of the stand that we built,


readers could instead build their stands around the dimensions of this hardware to avoid

having to cut down these metal pieces).

Table S4-3. Parts for a Microscope Stand that Allows for

Fine X-Y Adjustments in the Position of the Stage

Part (with Dimensions)

Microscope Stand

Base (8 in. x 10½ in. x ¾ in.)

Support Arm (3½ in. x 1½ in. x 8 in.)

Platform (3½ in. x 6 ½ in. x ¾ in.)

Assembly for X-Adjustments

Circular Disk (3.4 in. diameter and ¾ in. thick)

Platform (4 in. x 4½ in. x 0.2 in.)

Two Guide Rails (5½ in. x 1⅛ in. x ¾ in.)

Base (5½ in. x 6¼ in. x ¾ in.)

Assembly for Y-Adjustments

Platform (5¾ in. x 6¼ in. x 0.2 in.)

Guide Rails (6½ in. x 1⅛ in. x ¾ in.)

Hardware

Two Fully-Threaded Bolts (¼ in. diameter; ⅜ in. long)

Two Fully-Threaded Bolts (¼ in. diameter; 1 inch long)

Two Standard Flat Washers (¼ in. diameter)

Two Rod Coupling Nuts (¼ in. diameter)

Two Small “L” Brackets (2 in. x ⅝ in.)

Nineteen drywall screws (#6, course threaded, 1¼ inches long)

Other Supplies

Scotch “Extreme” Fasteners

Epoxy or Super Glue

Four Felt or Cork Pads

Hazards

Because hand and power tools are extremely dangerous and the associated risks of injury

are significant, readers should exercise great care when using any tools to build or assemble

this microscope, including wearing proper eye and ear protection as needed. Also, if unfamiliar

with these types of tools, readers should work with an experienced craftsperson for safety

reasons. Alternatively, in some schools, building several of these microscopes could be

assigned as a project for a shop class, which could make them for a science class.

Helpful Hints

Given our experiences in testing and refining the PVC version of the OPN Scope, we include

some helpful hints for its use.

First, because the PVC shell is built around a given filter cube, we suggest making the

internal dimensions of the shell slightly smaller than the cube. We make this suggestion

because it is much easier to sand down the inner sides of the shell slightly to provide more


clearance for the cube than it is to cut a new set of pieces in the event that the original ones

allow for too much “wiggle” in the cube.

Conversely, since one end of each PVC tube can be wrapped with electrical tape, we

recommend making the diameter of each hole slightly larger than the corresponding tube (e.g.,

by ⅛ of an inch). That way, a tube can be held tightly in place without having to perfectly

match the two diameters (an extremely difficult task as many carpenters are aware).

Finally, because some students may find it challenging to bring the PVC version of the OPN

Scope into focus initially, we suggest first using a commercially-prepared slide of a familiar

sample for this task. Then, once that image is in focus, the student can replace the slide with

the fluorescent sample and make whatever fine adjustments are necessary.

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