Parallel Capacitor safety at 10 micron plate spacing

[Saint Elmo]

TL;DR Summary

To assess the viability of a parallel capacitor at a 10 micron sheet distance.

Hi all. This might be a complex thread or line of questioning if the first question passes the human safety test. I was advised to post at undergrad level. I myself am a layperson without an education in physics/maths so if anyone would find the patience to explain answers in terms a layperson could understand it would be greatly appreciated.

A parallel capacitor with sheets approx 100mm sq. is applied a 5v charge. Is it a real world expectation that if these sheets are separated by a distance of just 10 microns that the capacitor can achieve an electric field of 500kv/m? Is a capacitor at this v/m and size lethal?

Many thanks

Elmo

 

[berkeman]

Welcome to PF, Elmo.

5V is not a lethal voltage for humans, unless you have direct access to things like heart muscle or brain tissue. So for direct skin contact, no. The strength of the electric field is not the determining factor, the voltage and available current at the voltage are.

The main question here is whether the dielectric between those plates can withstand that electric field without arcing through. To answer that, search on dielectric breakdown. For a vacuum or gas as the dielectric, search on Paschen Curve

 

[Baluncore]

A parallel capacitor with sheets approx 100mm sq. is applied a 5v charge. Is it a real world expectation that if these sheets are separated by a distance of just 10 microns that the capacitor can achieve an electric field of 500kv/m? Is a capacitor at this v/m and size lethal?

There will need to be a dielectric between the plates to maintain the separation and prevent breakdown due to dust getting between the plates. What dielectric is between the plates?

If the capacitor was charged to 5V, then the plates separated from 10um to 100um, or one plate slid sideways 90mm, the voltage could rise by the same factor, to 50V. At that point it is no longer a low voltage circuit and the regulations change.

 

[Saint Elmo]

Thanks guys,

So I'm looking at the breakdown of air which seems to be 3million v/m? Which was to conveniently bring me to a follow up of how this electric field might be maintained under airflow of maybe 30-60 cfm. If air is the dielectric does it have to be still? (and sterile)

If one needed to pump air through this electric field could mesh capacitors be used (as shown here to provide 75%-88% of the capacitance of solid sheets?)
https://www.quora.com/If-a-capacito...re-mesh-how-would-its-effective-area-be-found

If the dielectric is a solid (as opposed to gas) but in a mesh configuration between two mesh charged plates does that negate the electric field in the mesh gaps for air to pass through? Does contamination risk make it impossible to direct airflow through an electric field using capacitance @Baluncore?

And the increased distance of 10um to 100um as an example... does this change or maintain the v/m? If it was performed mechanically from lower viltage could it be exploited to extend a field or does the v/m drop in proportion to distance? (i'm guessing it does but...)

Elmo

 

[Baluncore]

I think you would do better here if you explained what you are trying to do, and why you are doing it.

 

[Saint Elmo]

I think you would do better here if you explained what you are trying to do, and why you are doing it.

OK,

was going to get round to it eventually but did want to avoid egg on face if a non runner from the get go or if a health hazard.

I am trying to see if it is physically viable to blow a certain airborne virus through a 500k+ v/m electric field before it gets inhaled while maintaining optimum airflow and use capacitance to generate that field (and importantly without electrocuting anyone).

Six to eight figure EFs were shown to damage the physical structure of Sars2 and can do it in sub microsecond times which might be conducive to fast airflow. If it was possible to use electricity as the "filter" instead of or in conjunction with regular filters it might work in a single pass (of air) and clear a space more efficiently of viable virus. Have read extensively on the Sars2 subject but physics is relatively new to me (and mostly through studying same).

The why is because despite popular belief, it still exists. Also very unlikely the last airborne virus to affect humans.

 

[DaveE]

Your air will have to be super clean. The electrostatic field will cause lots of stuff to accumulate on the plates (or as close as it can get), maybe even your viruses. Sometime later you will have an arc which will probably also inactivate some of the virus particles. I would guess most of the virus particles will be stopped by the dust filter upstream.

 

[sophiecentaur]

was going to get round to it eventually but did want to avoid egg on face if a non runner from the get go or if a health hazard.

I can't see where there could be any "health hazard" if the total PD is only a few volts. The problem would be to get the area and spacing of the plates good enough with air spacing.

This link is an ebay page with working air spaced variable tuning capacitors for radio sets. Look at some examples and their prices; it's non trivial to build one, I think. But you could buy one ready made and use it (in an enclosed system)with a few KV across it. Hi volts would allow wider spacing and there would be much less chance of clogging

Funnily enough, we just bought one of those electrical insect killers and have been listening to rifle cracks as flies go into it. The dangerous voltages inside it don't get out to us users!

Another thought: the field wouldn't need to be static. A high AC voltage would do the same damage to viruses passing through and wouldn't build up dust in the same way as a DC supply would. You'd probably still need a coarse pre-filter though.

 

[Saint Elmo]

Thanks @DaveE

So on that note could one negatively charge another plate (MESH) further upstream again to trap as much gunk and virus as possible before even hitting the dust filters. I'm basing this on the premise that particles in the air are mostly positively charged, (the reason negative ionizers work to force precipitation of airborne particles) and also that respiratory aerosols are polar and will assume a negative charge in the presence of a negative field?

OR

Could a positively charged plate (MESH) reject positively charged dust aerosols and particulates further upstream and trap virus in polar respiratory aerosols saving even the pre-filter?

And since neither of these theoretical mesh plates are part of a capacitor what safe voltage would they require to affect aerosols?

 

[Saint Elmo]

I can't see where there could be any "health hazard" if the total PD is only a few volts. The problem would be to get the area and spacing of the plates good enough with air spacing.

So only looking at the workings of capacitors for a few days and witnessed some threads (not here) saying they could be harmful even despite low voltage input as they still could store v high amounts of electricity??

And the electric field requirements to kill viruses of hundreds of thousands or millions of volts per meter didn't sit well but I'm told that's a non issue :)

Another thought: the field wouldn't need to be static. A high AC voltage would do the same damage to viruses passing through and wouldn't build up dust in the same way as a DC supply would. You'd probably still need a coarse pre-filter though.

Thanks for the tuning capacitors lead, will chase. That's interesting.

I have on my notes that 120v/240v would give me 1.2/2.4 million v/m at 100um spacing for a room cleaner. But also looking at a very portable and wearable design, hence the 5v at only 10um spacing to achieve a 500kv/m EF and the safety concern. But any design would be an enclosed unit.

The flipside here is decreased airflow and/or unacceptable fan noise due to the pressure drop from the dust filters. Efficient treatment with electricity, if the plate spacing would permit, might allow for a lower efficiency pre filter and thus better airflow and lower fan noise.

 

[sophiecentaur]

to trap as much gunk and virus as possible before even hitting the dust filters.

That gunk could be crawling with virus. You'd need to deal with that later.

 

[Saint Elmo]

That gunk could be crawling with virus. You'd need to deal with that later.

That's true but that filter could be a virucidal like copper.

The type of transmission (fomite) results in less severe acute stage disease than respiratory transmission. So ultimately better collect it and deal with it than breathe it.

But you're right it might need periodic uv treatment or something.

That's why i wondered if electrostatics could be used somehow to reject dust/gunk but trap 'polar' respiratory aerosols and how would it interact or compete with airflow. Airflow in versus charge?

 

[sophiecentaur]

@Saint Elmo But the air from this device wouldn't need to be any less dusty than normal so, if you avoid DC voltages, the clogging problem would be less. Do the sources you have read actually insist on high DC fields? Do they have evidence / opinions about AC / RF vs DC?

Also, if you are thinking in terms of high E fields, why not consider spikes which have high enough fields around the tip to cause ionisation of air

And UV is a well known technique for sterilisation (UV cabinets have been in use for Hairdressers' equipment for some while now.

There is a wealth of information about all this stuff.

 

[Saint Elmo]

But the air from this device wouldn't need to be any less dusty than normal so, if you avoid DC voltages, the clogging problem would be less. Do the sources you have read actually insist on high DC fields? Do they have evidence / opinions about AC / RF vs DC?

Also, if you are thinking in terms of high E fields, why not consider spikes which have high enough fields around the tip to cause ionisation of air

And UV is a well known technique for sterilisation (UV cabinets have been in use for Hairdressers' equipment for some while now.

There is a wealth of information about all this stuff.

@sophiecentaur I read the paper again (link below) having skimmed some of it previously. Results were generated using atomistic simulations of protein structure. Standard procedure apparently. There is no call for how field is generated, just that it generates a 100kv/m - 10million v/m. (max 3 million i assume for dielectric of air). The virus only needs ~1 microsecond or less in such fields to suffer severe and irreversible structural damage to the spike protein. The time scale is critical due to fast moving air and that's why I think "electricity" would be more favourable than UV. For UV the best info I had found was destruction in I think 10sec at 6cm.

AC would as you say make much more sense for a room air cleaner. The paper actually concludes with a call for use of E fields within filters.

The whole DC thing is coming from a separate portable design but battery powered. With a capacitor, a moderate electric field can be achieved with 5v. It might not be a runner as the filtering efficiency gained in disabling the virus with an EF might come with a cost of impeding airflow, more so than just using a very efficient HEPA filter. It all hinges on spacing as discussed. 9v battery may make more sense.

But finally learned today that capacitor spacing can be increased and still maintain EF between the sheets provided that the battery is disconnected first. Was hoping this was the case. This potentially could allow for mechanical separation of the plates once a desired EF is reached. Capacitance drops but field holds strong in spite of increased distance. So, does that raise options of a very small array of caps parallel to airflow which are charged to create required EF, disconnected, and then mechanically separated (different power source/battery) to allow max airflow? The pre filter then could be reduced from HEPA to a lower efficiency filter with higher flow rate as the EF handles the virus. The combination maximises efficiency. The rate of field dissipation and leakage etc. would need to be worked out for how long the capacitor lasts.

I love the idea of harnessing spike voltage to damage the virus spike. But I don't know would it all be as measurable or containable as capacitors? It would have to reach same EF strength range. I don't know how one would approach a design. Ionization of particulate matter might be one of the reasons the virus is getting into the air in the first place so spikes would have to crete very specific E fields to damage the virus spike protein.

PS: RF= over my head, i'll have to get reading.

https://www.nature.com/articles/s41467-021-25478-7

 

[Baluncore]

One fundamental problem is that a 10um gap is not comparable to 1 cubic foot of air per sec. The air velocity needs to remain subsonic. I see no simple way to geometrically arrange the accurate conductor separation and airflow.

A mix of techniques might work. Use UV to ionise particles in air, approaching an electrostatic dust separator. The separator has a hot wire collector grid to burn the dust immediately on contact. HEPA filters might also be used.

 

[DaveE]

But finally learned today that capacitor spacing can be increased and still maintain EF between the sheets provided that the battery is disconnected first. Was hoping this was the case. This potentially could allow for mechanical separation of the plates once a desired EF is reached. Capacitance drops but field holds strong in spite of increased distance.

Nope.

 

[renormalize]

Nope.

Not sure why you say this. The E-field between the parallel-plates of an ideal vacuum-filled capacitor of area $A$ and separation $d$, and which carries a charge $Q$, is $E=\frac{Q}{\varepsilon_{0}A}$ (neglecting fringing). This is independent of the separation $d$ between the plates. With no external connection (or leakage), the charge $Q$ and thus $E$ remain constant even as $d$ changes. Of course, it requires work to increase the separation of the plates. That work increases the voltage difference $\Delta V$ between the plates, which keeps $E=\frac{\Delta V}{d}$ constant.

 

[DaveE]

Not sure why you say this. The E-field between the parallel-plates of an ideal vacuum-filled capacitor of area $A$ and separation $d$, and which carries a charge $Q$, is $E=\frac{Q}{\varepsilon_{0}A}$ (neglecting fringing). This is independent of the separation $d$ between the plates. With no external connection (or leakage), the charge $Q$ and thus $E$ remain constant even as $d$ changes. Of course, it requires work to increase the separation of the plates. That work increases the voltage difference $\Delta V$ between the plates, which keeps $E=\frac{\Delta V}{d}$ constant.

Yes, you're right. That was because I was typing faster than I think. I was thinking the voltage didn't change. Which is absolutely not what the OP said. Oops!

 

[Baluncore]

But finally learned today that capacitor spacing can be increased and still maintain EF between the sheets provided that the battery is disconnected first. Was hoping this was the case.

That would make it a physical "parametric amplifier".
Charge a capacitor; C = Q / V, to a set voltage.
Then disconnect the capacitor. The charge will be fixed at; Q = C⋅V.
Separate the plates of the capacitor to reduce the capacitance.
The voltage will rise. V = Q / C.
The possible voltage change is not really significant when you consider the capacitance can only fall by a factor of about 10. It would be easier to have fixed capacitors, then raise the supply voltage by a factor of 10.

 

[sophiecentaur]

One fundamental problem is that a 10um gap is not comparable to 1 cubic foot of air per sec. The air velocity needs to remain subsonic. I see no simple way to geometrically arrange the accurate conductor separation and airflow.

This is very relevant to the realisation of a practical system. Fact is that there is no new technology in the OP's idea and I'd suggest that dealing with viruses in this way would be standard practice (by now) if it were feasible. I know that argument may be questionable and " it hasn't been done yet" can appear to be lazy reasoning. This is essentially a practical problem and the urgency for finding methods for control of airborne viruses must have stimulated loads of attempts up-scaling from a small lab experiment to a system for treating many litres per minute.

Afaics, the paper that the OP quotes is based on a theoretical molecular model and I could find no mention of how to achieve the sort of fields involved. No engineering at all??? Perhaps the title of the thread should have been "How to obtain a field of tens of kV/m across a parallel plate air filter" Also there seems to be a suggestion in the paper that the exposure time to damage the virus would only need to be 1 microsecond so low frequency RF would be very suitable (and handleable).


The thread has had to morph into a teaching / learning exercise for the OP and caused distractions from the main Engineering Considerations . Many of the above posts seem not to have appreciated the OP's naive view of the subject. The mentions of vacuum capacitors and dielectrics may have produced more confusion than clarification, I'm afraid. Great for a chat and perfectly correct but not what the OP needed. (The 'I' grade of the question was a bit misleading, perhaps.)

There are some initial assumptions about the basic idea that instantly knock it on the head (see the above para). Why is 5V somehow a necessary working voltage?; spacing would need to be microscopic which is just not practical. Plenty of safe, portable equipment has many kV circuitry inside it so why the 5V restriction? (Easy to obtain 5V power source and to work with, perhaps.) We can conclude that there has to be much more than 5V involved - but so what? The construction of the old air spaced variable tuning capacitors is the way it is for good reasons but those are not subjected to a high through-flow of air.

 

[Baluncore]

Also there seems to be a suggestion in the paper that the exposure time to damage the virus would only need to be 1 microsecond so low frequency RF would be very suitable (and handleable).

I can usually quickly collapse the requirements to a geometry that might work, but this one is taking a little more thinking outside the box. I am thinking maybe an inductor rather than a capacitor.

Imagine a single layer coil, wound as a two start helix, with spaced bare wire. Supported by longitudinal insulators. Air flows along the air core and must escape through the surface of the helix, between adjacent turns of wire. The voltage between alternate wires provides the gradient required. That could be excited by AC, like an RF transformer, made resonant with a capacitor.

A similar, single start coil, could be operated as a self-referenced transmission line. The microwave frequency would be adjusted to make the circumference half of a wavelength. That has maximum differential voltage between adjacent turns. We do NOT want to make a Tesla coil.

 

[sophiecentaur]

Imagine a single layer coil, wound as a two start helix, with spaced bare wire. Supported by longitudinal insulators.

If this is resonant then would the E field be uniform (or high enough) over your helix length? I can't actually picture what you are trying to describe. What sort of frequency would you be using.

But, before we get carried away with designs, it's worth while looking at what that paper has to say. Ifaics, it's a theoretical molecular model which they claim can be changed / neutralised by an external E field. I couldn't find any experimental results. Perhaps, when there's more evidence of the general principle, some useful designs could emerge but is there any point in following this any more until their system is actually shown to work. [ Edit: if the general principle is true then there should be many chemical process that use it. I'm no Chemist and I could be wrong.]

BTW I had a notification about a post which seems to have been withdrawn. I didn't know what to make of it as the EM basis didn't make much sense to me.

 

[TonyStewart]

I agree with all the expert advice so far and would like to add that I see very little use in using micro-ESD to eradicate CV2. when UV-C is so much more effective if tolerate. Both reply on the fact that energy increases both with decreasing wavelengths, shorter ESD times, faster rep-rates and lower breakdown voltages (BDV) with dust measured by particles per million. It also varies with pressure, the curvature of plate edges, medium, air flow, %RH etc.

For example, the EF gradient on two pins may discharge with high resistance at 1kV/mm or 3kV/mm in parallel plates, yet one-tenth of these levels in dusty high PPM environment or slight vacuum at Pachen minima.

I know many of the correlations with electro-static-discharge (ESD) or Partial Discharge measured in pico-coulombs (pC) and energy level and the detonation of the medium, ionization time and respective spectral energy bandwidths that are used in industry from deionizing clean rooms to creating dental X-Rays which can have biological effects. Even sustained sub-ionization levels have been documented in trade journals.

CV2 breakdown can best be done from the inside from your own innate immunity.
If you research medical journal reports and those related to CV2 prevention, you will find many both in TCM eastern culture, Ayervedic and global herbal and pharmaceutical supplements such as the University that created the MATH+ protocol and there site which has summarized all site research authenticated reports including NIH.

In short; ESD can create broadband RF and UV just like welding but at macroscopic lower energy levels. So I would use your enthusiasm to learn Physics with internal treatments like , sleep exercise, and supplements. I stay with a friend who had CV2 last year but never had any symptoms or +ve PCR results. I use many supplements at age 70, daily 4k brisk walks to 12k reg. walks if golfing and use 3 mg of Nigella Sativa oil produced by 31 countries and sold on Ebay, Amazon etc. and never had a bad cold or CV2 for I don't know how long.

I also am familiar with Dr. Been's CV2 weekly podcasts and many others.

But I believe ESD in micro-capacitor possibilities are slim to none as stated so far.

 

[Baluncore]

But, before we get carried away with designs, it's worth while looking at what that paper has to say. Ifaics, it's a theoretical molecular model which they claim can be changed / neutralised by an external E field.

I understand the concept of tearing molecules apart with electric fields. If that is possible, then how might it be done?

I can't actually picture what you are trying to describe.

I remain deliberately open and vague while contemplating possibilities.

Two ports, one is the inner core volume of the helix, the other is the outer volume. To pass from inlet to outlet, air must flow between adjacent turns where the E field has been maximised.
https://www.arrl.org/files/file/Technology/tis/info/pdf/9708033.pdf

 

[TonyStewart]

TL-DR; 500 kV/m = 500 V/mm = 5V/um

This may be the breakdown of dirty air ( > 1 million particles /cu.ft. particles in air) or about 15% of clean dry air in a parallel plate breakdown voltage BDV. But it is the repetition rate of xx nanosecond discharge rates that control avg. energy levels. It could be sharp edge or point breakdown levels with less dust.

This is something I wrote a few years ago related to microscopic discharges for publication in "Transmission" a power line industry magazine where I knew the editor as a former UHV manager of R&D at ABB (where he conducted tests at >= +/- 0.5GV)

We have come a long way since John Sealy
Townsend in 1890 with his discovery of
"Avalanche Discharge", Negative Resistance,
Oscillation modes, EMI and formula for computing
Corona Inception Voltage in a charged gap.
Later F.W. Peek improved on this to create
Peek's Law. Now we just call it PD if inside or
Corona if outside because it is more rapid, easy
to hear/see, but it can also be inside. But all
Corona starts from PD and all PD starts from
a little contamination in a pure dielectric{insulation}.
================
Technical stuff
The E-field and its derivative are the prime forces that accelerate charged particles. When many capacitors are in series with HV, the voltage is largest across the smallest capacitance such that each pair of particles has the same Q=CV flowing through them. Moisture lowers the impedance 1/80 because its dielectric constant is 80 times dry air. It may be hard to predict when lightning strikes of an unknown microparallel plate will discharge, but it will certain never reach levels that you stated and are unlikely to exceed 3kV/mm or 3V/um by any significant amount unlike hard vacuum or something is added to raised the BDV threshold.

This will result in an avalanche effect ( negative resistance) just like a gas tube, lightning, and somewhat like other negative resistance semiconductors.The difference bein in air with H2 and O2 the air combusts usually with a visible spectrum and higher by breaking down the molecular chain into discrete molecules then with >4% Lower explosive level (LEL) for H2, it detonates. This ionization process can create UV which I believe the researcher you are reading (link pls) believes that with a high enough repetition rate , it can kill CV2 using Friis inverse square loss for distance from the e-Field. I believe this is a pipe dream. Just like RF can cause cataracts in eyes from conversion to InfraRed so too can arc welding and microarcs from this potential invention next to the skin.

Again if disinfecting food and other products, UV-C is a far better approach.

p.s. I wish I could cite all the research I did on this subject, but it is too lengthy and not useful for this thread.

 

[TonyStewart]

Around the same time, Physicist, Maximilien Toepler derived Toepler's Law (1906) and an the extended version where the Arc Resistance, R[Ω] is inverse to the total discharge, Q, measured in Coulombs [C] = [Amp-seconds]. This RC also limits the rise time in a complex way then ionization turns into negative resistance by the chain reaction of molecular breakdown. There is also correlation between spectral BW & risetime. Trise= 0.35 /f -3dB. But also energy levels as he showed the negative resistance is inverse to the current flow of the discharge.

I have seen photographs of ESD pulses around 5~8 picoseconds but just related to electronic damage protection from OverStress a.k.a. EOS/ESD)

Scientists have contributed over 10,000 publications on PD characteristics and measurement methods. (MS Scholar & popular MS or PhD thesis topic)

Although Toepler being German discovered it independently of Townsend, English, the naming of Laws of Physics is a bit murky here in my mind. He is certainly credited by those who produce the best PD detection equipment. But his contribution is worthy from his extensions.

 

[DaveE]

p.s. I wish I could cite all the research I did on this subject, but it is too lengthy and not useful for this thread.

Thank you.

 

[sophiecentaur]

To pass from inlet to outlet, air must flow between adjacent turns where the E field has been maximised.

Would that be any better than tuning a parallel plate capacitor (obvs many interleaved layers) with an inductive drive circuit? Wouldn't the high impedance of a parallel resonator achieve what's needed? Not a lot of power would be needed with a high Q circuit.

But we really need to ask why this isn't already an established process. Airborne viruses have been around for a long time and they've been identified as a serious problem problem for years. UV seems an ideal (ready made - boil in the bag) solution.

[Edit: would we be wanting a discharge in the unit? I don't think so. That would reduce the field which is hardly what's needed. Wouldn't a suitable design keep the voltage below breakdown?]

 

[Saint Elmo]

One fundamental problem is that a 10um gap is not comparable to 1 cubic foot of air per sec. The air velocity needs to remain subsonic. I see no simple way to geometrically arrange the accurate conductor separation and airflow.

Thanks @Baluncore for all the input. I imagined two possible configurations. The fan sizes I was looking at were between 80mm and 120mm, so say 100mm avg and it's in a square housing. So that's sending air down a square pipe (a very short one but same dimensions). I had pictured the fan as being outside a square window blowing virus indoors.

Config 1 was a mesh positive plate covering the whole "window". Directly behind that, a mesh negative plate. They start 10um apart just to achieve desired voltage then get pulled apart mechanically (after disconnection from battery). The distance has to be enough for incoming virus to be affected for 1 microsecond and if the electric field can't maintain constant at that distance another mesh plate is added etc.

I only know that mesh capacitors are possible. I have no idea how large those mesh gaps could be (um or mm?) and if those gaps maintain the field, affect leakage, arcing etc?? But it's not necessarily a 10um bottleneck.

Config 2 The capacitors are more like venetian blinds (open) and solid. Imagine 5 pairs 10um separation per pair to achieve voltage. Then pulled apart until they are all eqidistant, but the top and bottom capacitors are flush with the base and ceiling of the "window" so virus has to pass through the EF. The depth of these capacitors are such that the virus spends minimum one microsecond in the EF depending on velocity.

Importantly, I had read in the last few days that the volts per meter does not dissipate until the plates are moved farther apart than their actual size?? They didn't specify length or width but for the venetian blinds (x10) that's 1cm ea "depth" (worst case) would allow around a centimeter distance between caps (or 11mm) and I think that config covers our 1 cubic foot per second of airflow... thinking microseconds brings that to under 3 cubic cm?

If that is incorrect about the v/m being a constant until they reach a distance matching the plate size or greater then those assumptions are obviously misguided.

Another thing, the 500kv was to cover bases but is kind if arbitrary. The study predicted destruction of the spike at 100kv - 10million. The 5v was simply to work in a wearable with a rechargeable battery. If that was 9v and the target EF was 100kv/m then the starting distance before separation could have been 90um. Not as microscopic.

 

[Baluncore]

Would that be any better than tuning a parallel plate capacitor (obvs many interleaved layers) with an inductive drive circuit? Wouldn't the high impedance of a parallel resonator achieve what's needed? Not a lot of power would be needed with a high Q circuit.

The capacitor has large plate area, so the length of airflow is increased. I prefer to have that capacitance and voltage gradient between two adjacent turns of an air-spaced coil. That has much greater airflow than long flat slots. A two-start wound coil would work with DC, or with AC. A single-start coil would need to be a parallel wire transmission line, or a slow-wave structure.

But we really need to ask why this isn't already an established process.

Those who say it cannot be done, should not interrupt those who are doing it. I look for novel solutions, not other people's problems.

[Edit: would we be wanting a discharge in the unit? I don't think so. That would reduce the field which is hardly what's needed. Wouldn't a suitable design keep the voltage below breakdown?]

Continuous breakdown is not wanted. There would be a breakdown discharge when something big entered the space between two turns, but the supply should recover quickly, and blow out the ash, or fail-safe, by shutting down the airflow. Maybe design the coil separation to operate at 100 volts, so air discharge does not prevent continued operation.

 

[TonyStewart]

The characteristics on an arc are similar to an SCR. Trigger voltage, conduction resistance(on), insulation resistance (off) holding current (DC) and zero-crossing extinguish current.

With a steady voltage above the holding current, you have a tiny plasma corona generator.
With a steady voltage and current limited below holding current, you have a tiny random relaxation oscillator or a flea zapper.
A resonant oscillator is slow to start depending 0.35/BW which depends on Q=fo/BW.
Without a theory of operation or a design spec, you have little to go on.

 

[Saint Elmo]

This is very relevant to the realisation of a practical system. Fact is that there is no new technology in the OP's idea and I'd suggest that dealing with viruses in this way would be standard practice (by now) if it were feasible. I know that argument may be questionable and " it hasn't been done yet" can appear to be lazy reasoning. This is essentially a practical problem and the urgency for finding methods for control of airborne viruses must have stimulated loads of attempts up-scaling from a small lab experiment to a system for treating many litres per minute.

Afaics, the paper that the OP quotes is based on a theoretical molecular model and I could find no mention of how to achieve the sort of fields involved. No engineering at all??? Perhaps the title of the thread should have been "How to obtain a field of tens of kV/m across a parallel plate air filter" Also there seems to be a suggestion in the paper that the exposure time to damage the virus would only need to be 1 microsecond so low frequency RF would be very suitable (and handleable).


The thread has had to morph into a teaching / learning exercise for the OP and caused distractions from the main Engineering Considerations . Many of the above posts seem not to have appreciated the OP's naive view of the subject. The mentions of vacuum capacitors and dielectrics may have produced more confusion than clarification, I'm afraid. Great for a chat and perfectly correct but not what the OP needed. (The 'I' grade of the question was a bit misleading, perhaps.)

There are some initial assumptions about the basic idea that instantly knock it on the head (see the above para). Why is 5V somehow a necessary working voltage?; spacing would need to be microscopic which is just not practical. Plenty of safe, portable equipment has many kV circuitry inside it so why the 5V restriction? (Easy to obtain 5V power source and to work with, perhaps.) We can conclude that there has to be much more than 5V involved - but so what? The construction of the old air spaced variable tuning capacitors is the way it is for good reasons but those are not subjected to a high through-flow of air.

@sophiecentaur thank you for your comments. 5v / 9v is admittedly based on assumed limitations for powering lightweight wearable devices. And being able to run this with a disconnected battery using plate separation sounded like a very attractive effect to power ratio. I'm unaware of multi kV battery powered equipment (wearable) .... what size equipment/battery packs are we talking?

Also, can't deny the point that the paper is simulated, (therefore not yet proven real world)

And as importantly, the premise here is that an EF takes over much of the the anti viral work of HEPA thus allowing a downgrade to lower filtration efficiency like MERV13 or MERV8 and thus an upgrade in flow rate. (Assuming that capacitors could be spaced much better than HEPA fibres). This improves overall efficiency and may handle the virus in one air pass. 100% efficiency with fast flow rate. There's an oversight here on my part. All of this would assume the next pandemic is caused by a virus. The previously quoted paper notes that virus spike proteins are unusually susceptible to moderate EFs. If the next pandemic was caused by airborne bacteria, the filters that remove bacteria have been downgraded and replaced by an EF which is probably ineffective against bacteria.

 

[sophiecentaur]

I'm unaware of multi kV battery powered equipment (wearable) .... what size equipment/battery packs are we talking?

You don't need a 100kV battery; that would not be convenient or cheap.12V batteries are good for starters and the circuitry would be low voltage until the output. A resonant transformer would give you kV only where needed.

This improves overall efficiency and may handle the virus in one air pass. 100% efficiency with fast flow rate.

At this point in the (maybe) development of an idea like this, what's needed is small scale attempts to realise in practical terms what that theory suggests. What you're suggesting is that we could bypass the normal chain of development of an idea and arrive at some personal protection device. Any such development needs to be done by people with detailed EM knowledge. I think you have to take that on board.

was going to get round to it eventually but did want to avoid egg on face if a non runner from the get go or if a health hazard.

you said it. (Not a health hazard if done properly, though).

There's also the point that you would need a virus-safe working environment to test this stuff. (££££)