Comment on: Trabecular bone organoids, synthesizing earth-like gravity equivalents
Trabecular bone organoids – A micron scale prototype designed to study the effects of microgravity and degeneration – https://www.nature.com/articles/s41526-021-00146-8
Alexandra,
I received this note today about your work. I have been tracking most all the levitation technologies on the Internet for some time.
Then I realized that you probably know all this already, except maybe acoustic and electromagnetic levitation mathematics, sensors and field generators.
Let me just say, I like your work and think it has great promise to replace animal use for meat and fish production with industrial scale production methods. If you want to read my notes below you are welcome. I don’t want to bore you.
I think your work shows that stable random velocity gradients have been embedded in the genetics of cells. I wonder if those particular genetic biochemical processes can be found and changed. Interesting problems. I expect that a well maintained temperature or pressure gradient can substitute for a velocity gradient, since the molecules only see their local environment as movements and vibrations and rotations. I will look at all the necessary models; but, I have no way to actually test. I track these things because they shape the future of the human species, and everything ends up on the Internet.
Richard Collins, Director, The Internet Foundation
If you can tell me the molecular composition of the material, I can probably find a method that uses body forces, rather than surface forces. The simplest would be ultrasonic, but if I can get a better idea of the composition it will save me time learning what you might have in your preparations.
As I am thinking about this (looking at the fields needed), it occurs to me that it would be easy to add fluctuations that average to zero net velocity, but would be comparable to the environment on earth, where there is constant field noise – acoustic, electric, magnetic, electromagnetic and gravitational. Since the gravitational forces are supposed to be equivalent to acceleration fields, any of the other fields can be used for that. if the materials you are using can be scanned to get their impulse response. Low cost software defined radio (SDR) methods are the least expensive and most applicable. I don’t think you need to go below nanometer scale. It just depends on the acoustic and electromagnetic response of your material. If you use both, it is faster and easier to find small approximate response functions that are less expensive to compute in real time for driving whatever sources you might have. I say that (choosing acoustic and electomagnetic sources) because I don’t know what limitations there are for orbiting experiments. A small shielded container is probably what you are using, and there should be good people who can build it. It just takes a tiny bit of mathematics and some low latency detectors and a lot of data.
It is impossible to generate supporting fields with infinite fineness. But to replicate earth like fields with their usual mix of fluctuations would be not that hard. I am not sure if all the sensors and processors are available in low weight versions for testing in microgravity. Like I said, I think the easiest are the SDR methods, but there are many available approaches. There is an avalanche of these new techniques, all converging on the Internet. I try to keep track of all of them, and to be able to model and test the assumptions and performance and global impacts.
Some time ago, I reviewed quite a series of bone growth stimulation methods mainly acoustic, magnetic, electromagnetic. “Use it or lose it” comes to mind. Yes, when I just looked at – weightlessness bone growth electromagnetic – there are pulsed electromagnetic and other methods people have tried. So on earth you can use the body forces to create weightlessness and cancel the noise to simulate weightlessness, and in orbit you can use the body forces to create weight and generate earth-type noise environments at a molecular level. The energies of the fluctuations are less than the bond energies (you don’t want fields that also break bonds).
The earth’s gravity can be written as 9.8 (Joules/kg)/meter and that can be converted into electron volts per atomic mass unit by using the Faraday constant (times 1000 because of converting from grams to kilograms) which is 96,385,332.12 (Joules/kg) per (ElectronVolt/amu). So 9.8 (Joules/kg)/meter divided by 96,385,332.12 (J/kg)/(eV/amu) is 101.675 (nanoeV/amu) per meter. This is an average. Your individual molecules are each going to respond differently, and not all of them have something to grab onto electromagnetically. Most will respond to a magnetic gradient, just not so strong they tear apart molecules. You just multiply the atomic weight by roughly 100 nanoElectron Volts per amu to get the strain energy gradient that needs to be maintained inside the material at the molecules location. I can simplify that if you want to use acoustics. Nice problems you have.
The acoustics can solved to have a gradient comparable to what they would have on earth (or any other place) reasonably close. And since the generators are supporting the material, the feedback signals depend on reporting position and orientation. Positions differentiated twice give the accelerations. Somewhere you have to set a standard mass for what you have. I will have to think about that.
I worked in my 20s and 30s on satellite orbit determination and modeling the earth gravitational potential field (the old NASA GEM models in the late 1970s). I just have a lot to track now. I will see if I can scan a few hundred paper titles and abstracts of weightless research to see what people are doing. with Elon Musk throwing so much into orbit now and people talking about space tourism now, I expect the clients would be happier if they had a synthetic body force to make it feel close to earth. Like I say, it is hard to get very fine grain and have low cost and low weight for the sensors, field generators and computers needed. it does not have to be elaborate.
For the billions of people on the earth who do not have a lot of money, I try to make sure every new technology that comes up on the Internet is low cost, accessible, teachable, and open to all.
I was only going to ask you about the material chemical composition. But my description of the problem above is pretty close. Enough that I can write the programs or symbolic math to solve and test. I never quite know what is happening next. Did you also consider that if you use weightless methods on earth, it is probably easier to manufactures your meat and bone mixtures cost effectively? I think part of the problem of artificial meats and bioreactors is the gravitational settling. You can overcome that with bulk mixing, but the method I just described of mapping the impulse response of the whole, and then generating an appropriate 3D acoustic field to mix or stimulate growth at every location, would allow for volume methods. I have a picture of a large vat (20 meters diameter) where there are suspended clusters of cells. The 3D haptic methods for simulating touch, and the acoustic levitation methods can move small clusters and object in prescribed paths and trajectories. And apply forces to mix and form things like organic solids and soft tissues. Adding it all up, it is much further along than I had imagined.
It still depends on a lot of things coming together. And groups are so slow. That is a global problem on the Internet – all the groups are currently using PDF and other paper methods to share. I am trying to convince publishers and authors and collaborative groups to share their working computer models, datasets, calibration method and tools so that everyone on earth can be involved, helping and learning. I tell them all – don’t use it to create yet another monopoly to extort from people who cannot protect themselves.
I wrote the long note above and was going to file it. I re-read your title and saw “micron” and readjusted. I described creating fields for things like plants, people, food, objects of various sorts. Fields to simulate earth-like gravity in orbit, or weightlessness on earth, by creating the appropriate body forces with real time 3D measurement of the acoustical response of the object, solving for the appropriate adjustments with some criteria for the nominal shape and pressures. But your small tissue colonies would be much more appropriate to industrial meat production and tissue cultures and bio-organic processing. I just went over artificial meats again last week, since it keeps popping up on the Internet.
Since maintaining weightlessness on earth is expensive, and Elon Musk can move things from earth to orbit. I wonder if weightless manufacture of biochemicals might be economic. Ship the raw materials to orbit, and then drop them back to earth on the return trips. Elon Musk can move metric tons of carbon based materials, water and chemical to orbit. There might be a few things that would be better synthesized in weightless conditions. So much to check on. Your colonies should do better with 3D acoustic processing to hold things in place and move them around, and keep them compressed in in colonies of sizes best appropriate to growth. Interesting problems.
I just looked at the simulated microgravity groups. I put that on my todo list. It is not hard to map what groups are doing and what is also possible, But tedious.
(“simulated” OR “simulator” OR “simulate” OR “simulating”) (“microgravity”) “bioreactor” has 68,400 entry points now. Fairly mature.
Richard K Collins, Director, The Internet Foundation
