electrospinning +15kV and -4kV = 19kV

Fun. I helped Tom Kelly start Imago, the tomographic atom probe outfit which was eventually acquired by Cameca. It was fun, I got named on a patent, and spent a lot of money on airline tickets.

As an engineer, it's fun to get involved with atomic- molecular-nano stuff. And, if it also requires high voltages, so much the better!

How are you generating them? C-W (or variant) style multipliers?

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Standard high-voltage dc-dc converter modules. Most are proportional types, which means you add a control system for their supply voltages.

Win, If you need any tips or tricks for Espin diagnotics let me know. I spent 8.5 years in a pioneering Electrospinning lab. One of the first things to do is ditch the syringe pump.

Steve.

On a sunny day (15 Sep 2019 11:49:20 -0700) it happened Winfield Hill wrote in :

Circuit diagram? That sort of voltages reminds me of teefee HV. Would grab old monitor or TV ?

How much output current or power is required?

Depends on the carrier solvent, polymer concentration, forced or gravity flow, type of polymer, a ton of things. However a typical single jet in the lab is a few hundred nanoamps.

Steve

Are there any good publications from your lab? What did you replace the syringe pump with?

Winfield Hill wrote in news: snipped-for-privacy@drn.newsguy.com:

Is the ripple any issue?

With x-ray I know that the cleaner the HVDC supply, the cleaner the flux, and thus the better the contrast ratio of the imagery.

If the supply is overtly noisey, the flux carries so much of it that the image is very grainy and 'snow-filtrated'.

Seems all you need though are the 'degrees of separation' that 19kV provides and noise is not an issue as the stream 'spins' out based on the attraction, not something directly related to the HV excitation as far as time goes.

Search for Darrell Reneker for the publications. The Thesis of Tao Han and Han Xu are really interesting.

Air source can be replaced with a dual solenoid valve assembly with a small chamber between the valves, which dump into a reservoir. Open A, fill cham ber, close A, Open B, dump into reservoir, close B. This is my favorite way , short of a MFC, basically Delta Sigma with air. It was not patentable.

Or US patent 8,500,431, my former supervisors way, a Slip Round the Ring, W hetstone bridge for Air...

One of the better discoveries for quality control was that a carefully desi gned, linear white light source oriented along the straight segment of the jet liberated diffracted light, very much the classical "soap film colors" and you could infer the diameter of the jet from the pattern of the colors with a camera.

My job was imaging and measurement , using a variety of techniques, as well as design and build of apparatus.

A recent pub, my very simple hardware design, , is:

" A Customized Instrument with Laser Interferometry for measuring Electrosp un Mat Thickness" Review of Scientific Instruments 90, 075110 (2019); http s://doi.org/10.1063/1.5100137

Problem being since fiber mats are rough on the nanoscale, and are often e lastic, you need a way to define what the surface is, and what the test con ditions are. The instrument in the above paper is a start, it needs other n on-contact probes for the contact to get even better data, and I'm looking at how to do that. But for a quickly designed, sort of hastily designed, i nstrument, it works well.

Steve

Air pressurization is often superior to the syringe pump, as you remove the sneak conductance path back through the pump body. Air gives you finer con trol, and if were to look at the fluid pressure over time you'd fine air is smoother.

You can also get a lot of data with laser doppler, the velocities are in th e right range that a sound card or simple LabVIEW system sampling at 10 or

Other tricks involve dual cameras for 3D, I used to multiplex two NTSC came ras on alternating fields or alternating lines, to get stereo images with a frame grabber.

Dual wedge prisms in front of the camera lens, and a high end camera or a high speed camera also get you 3D.

A green DPSS laser aimed at the straight segment will get you diffraction p atterns that correlate well with single slit diffraction math.

Lasers work great for measuring individual fibers as well, and if the diame ter gets real small, the fiber's scattering pattern (at right angles to th e axis) corresponds to an isotropic radiator, and then the amplitude of th e scattering corresponds to the fiber diameter. Ended up reading a lot of Lord Rayleigh's work to calibrate that. Saves a lot of time compared to lo ading fibers in a SEM.

The shape of the jet "cone" contains a ton of information, but the trick is using a Fresnel lens light source with a mask to keep the direct light ou t of the camera, and only detect the diffracted light. As the fibers are s o tiny, light sources must be immensely bright for filming at high speeds. I ended up using CERMAX lamps and metal halide.

All of this was between ten and twenty years ago, and I'd love to go back to it with today's technology. Especially with modern LED.

I have a few newer methods for measuring jet current that I'm not ready to publish yet, I'll send you an email.

Ballast resistors on the order of 1 Gig work great for creating parallel je ts.

The methods for mass production are what I more or less can't discuss..

Steve

And one more easy one. While electrostatic deflection of the jet works well , stabilizing its wander can be interesting. One way is to put a say 5 cm d iameter #14 wire ring at the top, and shoot through it. Tie it to the nozzl e potential.

This works great, especially for imaging or if your using a drum for collec tion.

We ended up with various means for winding even layers, typically sliding t he nozzle assembly back and forth with steppers gets you amazingly uniform sheets. With the caveat that the spinning collection drum is very large com pared to the landing circle diameter.

Steve

We get to play with a lot of fun stuff, without spending a decade or so doing the undergrad/grad/PhD/post-doc thing, working on one thing.

So do I, first as a Research Associate and then as a Departmental Senior Te chnician. Toss in a few years of Field Service and Factory Training Engine er work away from the University. There are weeks that I am totally shock ed by the cool gear I get to work on, or design, or modify.

My outside client base was USAF, DOE, Medical, Entertainment, Research whe n I worked in private industry.

STEVE

I worked a couple summers in the electronics shop of a university physics department. Got to help the scientists do all sorts of stuff. Lot of variety, learned a lot.

That's apparently what Win does, helps science types with the electronics. Some physicists aren't too good with electronics.

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John Larkin does enjoy being Mr. Superficial. His business model seems to i nvolve him being asked to solve little bitty well-defined problems that hav e been defined for him by other people. He seems to have built up a stock o f potential solutions which he can tweak to fit in a week or two.

Technician. Toss in a few years of Field Service and Factory Training Eng ineer work away from the University. There are weeks that I am totally sh ocked by the cool gear I get to work on, or design, or modify.

when I worked in private industry.

Review of Scientific Instruments makes this obvious from time to time. I've published five comments there making just this point - not only were the p apers I was commenting on poor, but the people who had reviewed them for pu blication hadn't noticed.

The British equivalent - Measurement Science and Technology (which started off as the Journal of Scientific Instruments in 1924, a bit before the Amer ican equivalent) isn't anything like as bad, so it may just be American phy sicists.

Win started doing a Ph.D. in chemical physics - I finished one in physical chemistry - so it may just be American physicists who aren't too good with electronics. The delusion that electronics is just applied physics may a cu ltural problem.

No doubt some physicists/chemists/biologists believe some electronic engineers aren't too good with physics/chemistry/biology.