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Geranium Grown Graphene Thermal Transistors

Make plants grow a thin layer of graphene on their leaves. Graphene thermal conductivity could be influenced by shape or form or pattern. The pattern could compose semiconductance - thermal semiconductance.
  [vote for,

Teach a specific and prolific species of plant to grow graphene layers on their leaves, in such a form as to form transistors or semiconductors, except that these biological graphene semiconductor circuits do not rely on conductance of electricity, but heat. They constitute thermal semiconductors. The plants grow a thin layer of graphene on the leaf surface. The pattern is influenced to grow into a transistor arrangement. The energy is a thermal gradient and not an electronic potential difference.
Ian Tindale, Mar 09 2017

An Interview with Carl David Todd http://www.semicond...Todd/Todd_Index.htm
Recollections from the First Days of Transistor Technology [Ian Tindale, Mar 12 2017]

Variable Thermal Conductivity Building Material variable_20thermal_...building_20material
A previous design for a 'thermal transistor' of sorts. [Wrongfellow, Mar 14 2017]


       This is very beanangelic, [Ian].   

       One question (out of a very large number of questions that suggest themselves): what exactly is the thermal analogue of a transistor?
MaxwellBuchanan, Mar 09 2017

       I should not have to point out that the help file is over there on the left.
normzone, Mar 10 2017

       //thermal analogue of a transistor?   

       "A semiconductor is a substance...Its conductance varies depending on the current or voltage applied to a control electrode, or on the intensity of irradiation by infrared (IR), visible light, ultraviolet (UV), or X rays."   

       So looks like the semiconductor conductance can be controlled by varying the heat. Don't ask me if that's the answer to your question.   

       And just one random thought, use mercury in tubes, kind of going back to the roots of early computing, using standing waves in mercury to hold data.
not_morrison_rm, Mar 10 2017

       Don't ants and termites have the down low on heat diode layers. Leaves are a bit ablative when over stressed.
wjt, Mar 11 2017

       //Don't ask me if that's the answer to your question. // It isn't, really, because that's talking about using heat to control the flow of electrons, rather than heat to control the flow of heat.   

       I suppose a thermic transistor (which, annoyingly, can't be called a thermistor because they already exist) could involve a heat pipe, with a central constriction enabling a low-temperature control to freeze the working fluid and prevent the larger flow of heat.
MaxwellBuchanan, Mar 11 2017

       Hasn't someone already made the optical analogue of the transistor? (using lasers and stuff). And aren't light and heat basically the same thing, making this also the heat analogue of the transistor?
hippo, Mar 11 2017

       //aren't light and heat basically the same thing// Sort of, only not.
MaxwellBuchanan, Mar 11 2017

       // a low-temperature control to freeze the working fluid and prevent the larger flow of heat. //   

       You'd want a material with a very low specific heat, and a similarly low enthalpy of crystallization.   

       There are considerable practical difficulties...   

       <placeholder for more considered analysis>
8th of 7, Mar 11 2017

       If you build a circuit that works on the thermal analogue of charge, rather than thermal analogue of voltage or current, then this could be done. For instance, have a large hot end and a large cold end connected by a very narrow heatpipe. Now coil, around the heatpipe, a coiled coil which will act as the controller (ie, base). If the base is below the freezing point of the heatpipe fluid, then very little heat will be transferred from the large hot end to the large cold end.
MaxwellBuchanan, Mar 11 2017

       What you want is a material which varies its thermal conductivity depending on how hot it is.
hippo, Mar 11 2017

       Given that hot and cold water already exist in a domestic house's plumbing, is in not possible that weird gurgling noise at 2am is a sign of emergent AI?
not_morrison_rm, Mar 11 2017

       I'm tempted to ask why.   

       Plants already have an electrolyte system of roots and leaves. I'm mean this idea is all a bit la di da, photo-chemical based sentient plants not good enough for you eh ? They have to be all two dimensional trendy stuff.
bigsleep, Mar 11 2017

       Heat will still transfer through a solid, admittedly at a lower rate. What is needed is separation. If the base changes shape under temperature then a touching or non touching connection between hot and cold ends can be made.
wjt, Mar 11 2017

       I don't think there's really a thermal analogy of a transistor, because heat is not conserved. And without kirchhoff's laws, nothing would make any sense.   

       // a material which varies its thermal conductivity depending on how hot it is //   

       I believe that's one of the properties of vanadium dioxide.
mitxela, Mar 12 2017

       Are we treating graphene as if it has the same properties as a 'solid', though? The thermal gradients across (in both dimensions) a section of graphene, conductance controlled by a further application or reduction of thermal energy could result in transfer control. In other words, transconductance. Remember that the word 'transistor' is a portmanteau of 'transfer resistor', because of the effect of a controllable resistor. Remember that the use of the terminology of current and voltage in electronics denotes the flow of electrons, and the potential difference of electron energy, respectively (so, if there's a voltage, and you apply a load e.g a resistor, it allows a current of electrons to flow).   

       All of this is simply managing energy, nothing more. The same could apply to thermal gradients, tiny molecular level gradients. Look up acoustic phonon modes for graphene (acoustic so named only because it resembles in-phase air transmission of energy packets, to distinguish it from the other, optical phonon modes). Transconductance of energy in electronics is established, but a similar thing in thermal differences and thermal currents is likely entirely feasible in a graphene plane.   

       The idea of growing graphene 'transistors' is likely possible by formation biases at the molecular level. The way we make electronic transistors today is quite crude. The way they were originally made was even cruder, and quite heroic. I'll link to an oral history of Carl David Todd and his involvement in making transistors in the early days. I'm fairly sure any of us here in the halfbakery will find it a good read, so have a go at it (over several pages, but fascinating). And remember, this isn't so long ago - we haven't been doing transistors for very long at all, so don't allow their established present-day industry ways seem mysterious.   

       Finally, if we're going to grow intentionally deformed graphene forms, well, there are many precedents in nature that follow a 'planar' topology of growing cells in a sheet, and having a specific surface to those cells on one side. I thought of plants, leaves, because that's fairly obvious, although my first thought was a butterfly wing, but the scales on that are highly complex in themselves and deviate from what I was trying to get at by having a 'growable' graphene plane. Maybe an algal growth on agar or something would work better than geranium leaves, I don't know.
Ian Tindale, Mar 12 2017

       Another thing. The future, as time goes by, forwards, we'll be requiring more electricity generation. As robots and AGI take over and displace people and their jobs, as production and the general availability of goodies increases, and as life transitions into a post Industrial Age of meaningless pointless waiting to hurry up and die because everything is too expensive and there's no money and nobody wants anything you could possibly do, we'll find the requirement to generate electricity increasing. This means that electricity could become the prime currency (no pun intended) and the makers and gatekeepers of electricity could and are already hiking up the cost of electricity to painfully unaffordable levels.   

       One thing we'll have to do is to diversify technology away from being electrical-only. What we do with electricity is to treat it as energy, but a manageable energy, that can be made to do things we want it to do, and gain value from the results. Well, it doesn't necessarily have to be electrical potential difference.   

       Using water and water wheels and waterfalls etc to make an amplifier or a switch (or many switch-controlled- switches, i.e a computer), while maybe possible, is a bit silly. Heat, however, is the perennial enemy of the electronic circuit - transistors in particular are only at their specification at a specific temperature, and the act of doing their work creates (unwanted) heat. We could concentrate on just using the heat. Kirchhoff Slaw still applies (come to think of it, as would Thevenins and Nortons), as long as there are instantaneous distributed differences (those being controlled and manipulated).
Ian Tindale, Mar 12 2017

       Isn't heat that abstracted indescribable pattern. As soon as you transistorize the pattern it is not heat any more just another turtle and the next turtle down becomes heat heading into the dark matter of things.   

       The infinite patterns of energy mean boxing them perfectly means the last turtle is very very slippery.
wjt, Mar 13 2017

       It depends. On a large scale - that of domestic objects all around us, the thermal gradient behaviour is perceived as having certain properties that we're fairly used to. The room is cold, turn it up. The elecricity bill arrives. Turn the heat down again, the room is freezing again. That sort of dynamic. The bigger scale - thermal gradients resulting in weather - is not intuitive enough to predict accurately without the immense investment in supercomputing that we have now, and even then, well, you've seen weather reports. The astronomical scale of thermal energy is interesting, and possibly one of the most important fundamental energies to keep track of beside gravity. However, at the molecular level, and particularly on an unusual planar surface such as graphene, thermal difference acts more like a fundamental energy and not in the way that we think of 'heat'. This idea is all about doing transistor action, using graphene, knocking energy about that whilst atomic doesn't have to be electronic.
Ian Tindale, Mar 13 2017

       A multi-layered logic layer. Heat is a bit flighty, being pushed around by all the other energy patterns, I imagine the graphene heat wires would be be quite wide to stabilise the heat flow.
wjt, Mar 14 2017

       Or, it could be that flighty heat is a desirable property in doing this sort of thing. (Also, single layer, and analogue, so not necessarily multi layer, or binary states).
Ian Tindale, Mar 14 2017

       I was thinking more of having both electron logic ( or another logic mechanism) and heat logic in/on the one layer. Doesn't the brain have the neural network and a slow tidal chemical flood logic.
wjt, Mar 15 2017

       And the brain is actually a single sheet - one plane - but screwed up in a ball, like scrunching up a sheet of paper.
Ian Tindale, Mar 15 2017


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