Re: A better electron microscope

Aug 07, 2024 Last reply: 1 year ago 2 Replies


Scientists revolutionize microscopy by reimagining the logic of imaging


>
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> New method significantly reduces the time and damaging radiation used to image fragile specimens
> Date:
> August 2, 2024
> Source:
> Trinity College Dublin
> Summary:
> Scientists have devised an innovative imaging method using state-of-the-art microscopes
> that significantly reduces the time and radiation required.
> Their work represents a significant breakthrough that will benefit several disciplines,
> from materials science to medicine, as the method promises to deliver improved
> imaging for sensitive materials such as biological tissues that are especially
> vulnerable to damage.
>
> And chips?

The paper claims "Giving microscopists the ability to 'blank' or 'shutter' the electron beam on and off in a matter of nanoseconds in response to real-time events has never been done before."


It isn't true. The stroboscopic electron microscopes that Cambridge Instruments sold from about 1983 as electron beam testers could deliver a half-nanosecond wide pulse of electrons.


The electron beam microfabrictors we'd been selling for year could turn the beam on and off in less than 10nsec - I worked on the beam-blankers for both.


Scanning transmission microscopes do use higher voltage electrons, but that just means that the electrodes that blank the beam have to be longer. With a half nanosecond wide pulse, you couldn't make the plates too long for 2kV electrons because the transit time got longer than the blanking period and I had to invent a solution to get around that, but "a matter of nanoseconds" give you more wiggle-room.

A bigger problem for biological tissues is that they have to be dried before they can be put in a vacuum chamber and this process can distort them. They also usually need to be stained with a heavy element such as uranium for TEM and coated with gold or other conductive materials for SEM. John

There are "environmental SEMs" that work by differential pumping and can allow enough water vapour around a cold specimen to stop it dehydrating but not enough to scatter too many of the imaging electrons.

Their commercial success came after my time on electron-microscopes, so I don't know much about them. My boss from Cambridge Instruments moved on to FEI so he knew more, and had talked about them, but he died around

2010.

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