Shedding Light on a Luminescent Fungus

Editor,

Perhaps Garth Fletcher will find that his fungus is Piptoporus betulinus (Garth Fletcher, A Bioluminescent Fungus, Gallery, 7 October 2005; see Fig. 1).

Figure 1. Reader P. F. Jennings has identified this luminescent fungus as Piptoporus betulinus. This photograph by Garth Fletcher first appeared in A Bioluminescent Fungus, Gallery, The Citizen Scientist, 7 October 2005.

It's common enough in certain woods, apparently. And the luminescent quality is not unusual in fungi. Can it have something to do with the dim and dark environment of woods along the lines of deep-sea creatures that fluoresce and scorpions and other desert night dwellers that also do?

There are some pictures of Piptoporus betulinus here and here.

Best regards.

P. F. Jennings

Thanks very much for this identification. Garth Fletcher's photograph may be unique, for a search of some 300 images of Piptoporus betulinus on the web revealed none glowing in the dark. Readers, a nicely written feature about the phenomena of biological luminescence and fluorescence would be a welcome addition to The Citizen Scientist. If you are interested in contributing such a feature, please send a note here. Editor.

The Lead Ban

Editor,

The lead ban is having a major effect on the electronics industry (Are you Ready for Lead-Free Solder? The Citizen Scientist, 7 October 2005). Many electronic components are no longer available with tin/lead coated leads. Here at work we have a big concern about this ban as we make high reliability military and commercial avionics. You really don't want your autopilot failing because of a tin whisker or cracked solder joint. Much of the consumer electronics turns into junk in a year or so for other reasons so the problem is not as severe with consumer electronics. On the other hand, I am not sure how much effect this will have on amateur electronics builders. You can still use tin/lead solder with the lead free parts and the lead free solders work about the same anyway. So the only thing the amateur faces is the reliability issues that everyone else faces.

The way I see it, the big change that affects amateurs has already happened, and that is the change to surface mount parts with tiny close spaced leads and, the worst of all, "ball grid array parts." You can't get away with just a soldering iron when hooking up these new surface mount parts. Gone are the days of wiring up a bunch of DIPs in sockets. You now have to layout circuit boards and solder with a microscope and temperature regulated soldering iron.

Jim Hannon

Jim Hannon's comments are must reading for amateur scientists. Readers are invited to send "Backscatter" additional comments about this important matter. Editor.

Steam Battery Comments

Editor,

I just finished reading Mark Valentine's excellent article in the 7 October 2005 issue of The Citizen Scientist entitled "The Steam Battery: A Low-Cost Science Experiment Performed with Ordinary Materials": http://www.sas.org/tcs/weeklyIssues_2005/2005-10-07/feature1/index.html, and I'd like to make a few comments.

One problem I can see with the design of the experiment is that a variety of differing metals are being used at each electrode. This could lead to a problem with forming an electrochemical battery.

Mr. Valentine states that, "For example, the condensed water from breath should be relatively distilled, preventing it from acting as an electrolyte for an electrochemical reaction." I'm not completely convinced that such is the case. For example, some chemicals, such as hydrogen chloride and ammonia, go into and out of solution relatively easily, and cannot be completely eliminated by a simple distillation operation. While the amount of both of these particular chemicals should be somewhat limited in the human body, they may be present in minuscule amounts. Perhaps of more concern, though, is that human breath is composed of a rather significant amount of carbon dioxide, which can dissolve in water forming carbonic acid. While this is a relatively weak acid, it may participate in some electrolytic reactions. {This gives rise to a couple of additional experiments which may be conducted concerning the electrical conductivity of carbonated beverages, and whether such beverages would be useful as the electrolyte in an impromptu electrochemical battery.) One way to rule these effects out would be to use humid air from a non-biological source.

Also, note that the presence of solid electrolytes on the ESD foam hasn't been ruled out. The presence of such electrolytes could be activated by water condensed from the humidity. Thus, it may be informational to try washing some of the ESD foam in a distilled water bath to remove any residual solid electrolytes to see if this may offer an explanation of the potential being developed.

Another approach would be to eliminate as many of the differing metals as possible. The metal (plated steel? bronze?) paper-clip could be replaced by a plastic clip, or at least insulated from the electrodes by a layer of plastic. The aluminum foil could be replaced by a graphite electrode, which should be compatible with the ESD foam, since most ESD foams appear to be composed of a graphite loaded plastic material.

Elimination of the differing metal junctions should also minimize the chance that the potential developed is due to a thermoelectric effect (although the magnitude of the potential developed pretty well discounts that as the source of the potential, since most thermoelectric sources are of MUCH smaller magnitudes).

A control test, where warm, dry air is blown over the electrodes would be interesting to include in the data. This would confirm or disprove the presence of the humidity/moisture as the reason for the voltage being developed. It may also be interesting to conduct the experiment at varying temperatures (condensing and non-condensing) to assist in determining if condensed moisture is responsible for the potential being developed, or if the effect also occurs without condensation.

I think we can exclude effects such as MHD (MagnetoHydroDynamics), although this would be relatively easy to disprove by varying/reversing the magnetic field surrounding the device.

Just to cover all of the bases, it may also be useful to conduct the experiment in a darkened area to see if there may be a photoelectric effect contributing to the developed potential.

I'm sure that there are more variables to be considered. Often, one of the most difficult aspects of experiment design is in identifying all of the possible (and unintended) variables.

In any case, this is a good illustration of how amateur science may be conducted at low cost with everyday materials.

David W. Glass

More Steam Battery Comments

To the Editor:

Re: The Steam Battery: A Low-Cost Science Experiment Performed with Ordinary Materials

I would not have expected this result because of the conductivity of the ESD foam. The measured resistances suggest that my hypothesis is quite incorrect because the resistances are fairly high.

The fluctuation in data is expected (even if the electrical output is not), because a person cannot deliver consistent breathing either in flow rate or in content.

Seeing the highest voltage develop on the middle resistance material was surprising, too, because I would have expected more output from higher resistance material. The output voltage must drop as the resistance approaches zero, which makes sample 5 logical.

Mr. Valentine suggests that human breath produces distilled water. Yet, that is not entirely true. It contains carbon dioxide and heat plus other very small amounts of chemicals. This experiment should be repeated with a damp piece of foam heated at one end to eliminate heat as a cause of voltage. Radiant heat should suffice.

Another test would require generating water vapor from a non-biological source (e.g., a tea kettle) to eliminate CO₂ or other chemical contaminant as the cause.

It's highly unlikely that a water gradient, by itself, has generated the voltage. If it had without involving chemical reactions of the foam, then it could not sustain any voltage (and current) for long, if at all. According to the laws of thermodynamics, you can't get something for nothing.

I would have liked to seen the impedance of the DMM listed, which would provide an estimate of the current being generated and might have provided some hypotheses regarding the low voltages of the high-resistance foam. Perhaps, a DMM with a higher input impedance would have measured these voltages differently.

It's a really neat experiment that can be done quickly and inexpensively for those with appropriate materials at hand. I hope that Mr. Valentine will take on the challenge of some further testing.

Harry E. Keller, Ph.D.
President
ParaComp, Inc.
310-773-4293
www.smartscience.net

Mark Valentine Replies

Something common to both emails from Harry and Dave is a suggestion to use moisture from a non-biological source. Early on in the first crude experiments with ESD foam, I heated a cup of distilled water in a microwave, and the resulting steam produced a voltage across the foam. In fact, as a demo circuit, a "steam oscillator" was made in which the voltage from the ESD foam was connected to an operational amplifier that turned on a fan that blew steam away from the sensor. As the voltage in the sensor decayed, the fan was switched off, allowing steam to reach the sensor once again and starting a new cycle. As a side note this circuit used tricks learned from your engineering notebooks, Forrest.

To address some other remarks from Harry, I believe the mechanism responsible for the voltage is somehow related to condensation of water vapor. This is probably a psychological artifact of personal training and experiences with the "hot-point probe" used to tell whether a semiconductor wafer is "p-type" or"n-type." Those devices operate by generating a weak current from a thermal gradient. It's tempting to visualize that energy from condensing water vapor in the ESD foam is somehow creating a gradient of excitation in the foam in a fashion similar to the hot point probe. However, this is merely a starting point for further experiments. The purpose of presenting the effect in the first place is the deep desire to know what is actually going on, and it seems from the thoughtful responses so far the answer may come soon from a talented and curious community. I hope you'll continue to keep me in the loop!

To address some of the other questions, the DMM input impedance is 10 megohms, typically, and over 100 megohms in the 200 mV range. The meter is autoranging, so only the foam sample that read above 0.2 volts had the strength to break into the 10-megohm range. For this reason, the foam is likely to remain a sensor only, but certain samples may be sufficiently strong to rig in parallel or series and provide enough power to run a low-cost calculator, which will run on a few microwatts given the weak current consumption of some of the "$1.00" solar-powered models. Such a contraption might make
another interesting demo.

The observations about human breath not being totally distilled is definitely something to be considered. If there is chemistry going on within the sample, it's literally possible that time will tell, since the
reactions would eventually consume the material (unless the reactions are catalytic in nature). This should also make a good experiment. Certainly part of this process would involve contacting foam makers and getting their secret recipes.

There's a story behind how this effect was discovered. It is partly based on an accident, and mostly based on a friendship with a professor at Kansas State University who loves to teach and share his latest
research efforts. It also involves a loving wife who allows her husband to blow air through soda straws while she tries to watch TV.

Mark Valentine

Thanks very much to David Glass and Harry Keller for their letters and to Mark Valentine for his response. Readers who can find an explanation for the voltage produced in Mark's experiment are invited to send their reports to "Backscatter." Editor.

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