Insect Chilling Chamber

by Johan J Ingles-Le Nobel
Last updated August 31, 2017

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Killing insects is by far the most common method used by extreme macro studio stackers to get their specimen ready, but there's got to be a better way that doesn't involve killing.

I don't like killing insects so this is a project that's ready on paper and awaiting the right time for me to build it.

The Big Plan

Peltier cooler

A Peltier, a solid-state active heat pump which transfers heat from one side of the device to the other, with consumption of electrical energy, depending on the direction of the current.

These can be purchased directly from suppliers in the Far East and I have bought 3, but I am still not entirely convinced that this will achieve the desired result. Stay tuned...

The insect chilling chamber that I have designed on paper requires various skills to make, none of which I yet have, which is why it is taking so long. But the theory, I think, should be fine. Part of the problem here is that I cannot find any similar device anywhere, so there isn't really anything to base the design off other than trial and error on my part.

We know for a fact that insects will remain still in cold temperatures of 0ºC-5ºC , so in theory a chamber with a low temperature should create those conditions and enable a photographer to take an extreme macro stack of images. Sound easy but there are all sorts of engineering obstacles to overcome.

Observations

A cooled chamber is easy to source but building one for extreme macro requires special modifications. To allow for diffusion, I am using a 5 sides perspex shop display case, with a separate sheet for the bottom to be able to actually put the insect inside.

An opening will need to be cut in the side with some flexible thermal material that extends round the lens, so that I can put the lens inside without having to shoot through perspex, yet also keep the temperature cool. I suspect that I'll need to make this modular in some way to account for different lens and objective sizes.

I can monitor the temperature at various points inside the chamber with temperature sensors, and a nice to have would be the ability to set a target temperature then to have the thing beep when the sensors have reached the target temperature.

Arduino

Arduino microprocessor, the base for the device.

Arduino is an open-source electronic prototyping and programming platform allowing the creation of electronically programmed and controlled devices.

Lenses inside chilled chambers may lead to a possible condensation problem on the glass face, so allowance has been made for a small PC fan to blow the air across the face of the lens. Small, because a fan might lead to vibrations, which we want to avoid.

If there are too many vibrations then I may go back to a previous idea, which would be to use an aquarium air pump blowing air through a desiccant to remove and absorb the temperature released moisture.

With an insect inside a chilled chamber and a lens in a relatively inflexible position except for the Z-plane, some means needs to be available to move the insect in its own XYZ planes to make a nice angle to shoot the insect at. Various interesting materials like 3D printing or shapelock can be used to create the arms for a lightweight universal stage, ideally I'd like those arms to be controlled from outside the chamber, which requires motors controlled through Arduino. Stepper motors might seem to be an ideal solution but they require a current to keep them stationary. I have purchased various steppers and DC motors to test, but finding the worm drive mechanism to translate the motor rotation into efficient arm rotation (in which the motor doesn't bear the weight but the arms do) has been trickier. But I believe that I have found some, but small 4mm worm screws are expensive.

Electronic means need to be used to control the various parts of the device; the Arduino microprocessor platform looks to be ideal as it is relatively affordable and the programming is well documented. Arduino is already used to make all sorts of creations including stackshot-like stacking controllers.

The mechanism used to cool down a chamber must be out of the way and relatively easy to control. For the time being I have settled on some Peltier coolers which are relatively straightforward to program using Arduino although the power requirements are high. Although I was initially looking at using 3 Peltiers or even a peltier sandwich with fans inside to distribute the cooling effect through some large old Dell server heatsinks, I'm not entirely convinced that this is the best way to do the cooling as the convection effect of a very cool object may suffice.

Peltier cooling operates on a sandwich principle with -20ºC on the cool side and +40ºC on the hot side. To operate, Peltiers require a heat sink mechanism to absorb the heat on the hot side otherwise they burn out within seconds. I have purchased a Corsair Hydro water-cooling mechanism for a PC to do this for me, which is all also controllable through Arduino (ie the speed of the fans, speed of the pump). Copper is a good temperature transfer medium so I have some sheets of copper, which will be stuck onto the hot side of the Peltiers using silver oxide semiconducter glue with efficient temperature transfer properties.

It may prove neccessary to add other means to dissuade the insect from moving away from the spot that I need it to be to take the photo. For example, Insect-a-slip prevents arthropods from climbing out of traps, cages, or other containers and forms a slick barrier that prevents arthropods from obtaining a foothold on the treated area. It maybe useful to make an Insect-a-slip barrier.

Also, at the same time, a sugar coating on the target area might give a positive inducement for the insect to stay put. Or a jet of warmth, to make the 'stay here' area more attractive than other parts of the stems.

CO² can also be pumped into the chamber through an Arduino air flow sensor. CO² in high concentrations is an agent that reduces insect movement although insects assume somewhat unnatural poses if exposed to high levels. CO² can be purchased relatively cheaply through aquarium suppliers, it is sold precanned for underwater plant promotion.

Progress Report

At the time of writing, I have completed two Arduino courses, built 15 gadgets using Arduino, and sourced the base materials to be able to start construction. I'll resume working on this as the one of the next projects on the list, scheduled for Q4 2014.

Comments (24)

Article: Chilling Chamber
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Gene says...
To allow the objective to pass into the chamber without losing the specimen(s), we talked about using a modified objective adapter to serve as a pusher against a bellows. The bellows will be permanently attached to the chamber using a flange and the chamber will be secured to the breadboard. This idea may change.
10th March 2019 3:01pm
Gene says...
My daughter and her daughter have been exchanging science fair ideas, so this may be it.
10th March 2019 2:50pm
Gene says...
Regarding CO2 experiments, we discussed using a simple plumbing solution to pass a mix of air and CO2 into the specimen chamber. This is based on a computer fan mounted to a PVC tube. The tube also serves as a mixing chamber for the CO2. We discussed modifying a CO2 bicycle inflator to route CO2 into the mixing chamber. We need to develop a low cost solution for metering the CO2. Any ideas would be appreciated.
10th March 2019 2:47pm
Gene says...
Swagelock has small vacuum fittings (e.g., Swagelock SS-2-UT-1-2) and it may be possible to modify these to create a simple joystick like mechanism for the specimen holder (i.e., a clip attached to a small rod passing through the fitting. These fittings use the tension of a buna o-ring to seal against the tubing passing through the fitting in a fashion similar to a thermocouple feedthru. We discussed slipping a globe shaped metal bead to the rod passing through the fitting and remachining the fitting to act as a joystick-like pivot point for moving the specimen holder around. We are hoping the o-ring tension will hold the rod in place and will experiment to see if this is feasible. It may be possible to move the specimen up and down, rotate it and move it in angular directions bound by the internal shape of the fitting.
10th March 2019 2:38pm
Gene says...
My daughter and I have been brainstorming chamber ideas. We have been discussing a single chamber designed to perform numerous experiments (CO2, LED, simulated mating, etc.). We found short lengths of 6-inch diameter clear polycarbonate with clear end caps on Ebay. The exterior and interior of the tubes are glossy so we are considering sandblasting the exterior with a walnut shell material to create a matte finish. Since the interior of the tube is round, a length of vellum could be inserted into the interior of the tube. This should help with light diffusion.
10th March 2019 2:31pm
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