Atomic force microscope turns bacteria into maps of reality

Atomic force microscopes don’t “see” with light—they feel surfaces. In a new walkthrough, Ben Krasnow shows how an AFM can track probe motion at nine kilohertz, image bacteria from fermented soybeans, and verify laser-etched metal removal using electrochemical

A regular microscope lets you look through glass and lenses. An atomic force microscope doesn’t. In Ben Krasnow’s hands, the imaging starts at the surface—literally. The probe never sends out an optical beam to form a picture. Instead. it physically detects what’s there. repeating that scan thousands of times to build a height map of the sample. sometimes with resolution below a single nanometer.

Krasnow’s first demonstration is almost a test of nerves. The probe oscillates at nine kilohertz, which sounds precise and simple until you try to film it. He uses a stroboscopic welding camera filming near that frequency to visualize the probe head in action. It’s a glimpse of motion you can’t “watch normally. ” because it’s too fast—until the camera timing makes it legible.

Then the AFM turns biological. Krasnow begins with bacteria from nattō, fermented soybeans. He lets the bacteria multiply in a sterile growth medium. then centrifuges and washes them to clean up what’s floating around. To give the microscope a very flat foundation. he spin-coats a thin layer of gelatine onto part of a silicon wafer. Gelatine is electrostatically attracted to the bacteria, so it adheres them to the slide while he washes away other contaminants.

The payoff is clear AFM imaging of the bacteria. More than just seeing them, the scan reveals how the spin-coating step oriented them—showing the direction they ended up aligned in.

After that, the tour widens. Krasnow images silver nanoprisms and track-etched membranes. Track-etched membranes are made by using high-energy radiation and an etchant to cut very consistent. fine holes into a plastic filtration membrane—exactly the kind of small. structured features an AFM can map. He also images his laser-etched diffraction gratings.

With those gratings, the question isn’t only what the pattern looks like, but how the laser made it. Krasnow tries to selectively etch away the laser-exposed metal and then uses the AFM to verify that the metal has been stripped away. An acidic etch doesn’t work, a basic etch doesn’t work either, but electrochemical etching seems promising.

Across these projects. the through-line is physical verification: probe motion that has to be captured at nine kilohertz. biological samples prepared to be clean enough for reliable adhesion. and metal removal checked directly on the surface. The microscope isn’t just producing pretty images—it’s confirming what happened to matter at tiny scales.

If the idea of building your own AFM has been sitting in the back of your mind, there are DIY versions documented elsewhere, including one that can resolve individual atoms.

Krasnow’s video is paired with a note of community influence as well: thanks to H Hack for the tip.

atomic force microscope AFM Ben Krasnow bacteria imaging nattō gelatine silver nanoprisms track-etched membranes laser-etched diffraction gratings electrochemical etching