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Comment by shelkie | Hacker News Reader

Cool how they're using BNC connectors and ICs from the 1980's /s

First standout thing I noticed is the “patern generator” array of DIPs - admittedly without having dived into the paper, any answers from the hive mind what they’re doing?

I was focusing more on the "current to frequency" stage, which looks like an empty IC socket. As is the "pulse width counting" stage just a bunch of header pins?

I mean yeah, I get it, it's a prototype and a finished product will be on a $2 ASIC to drive the correct signals and etc. But I'm not up to speed on affinity sensors vs. traditional ELISA tech so <internet shrug>.

Nothing jumps out at me as being fishy here. There's what appears to be a small device mounted in the middle of that empty socket. It's also possible some of the rest of the pins on the socket are being used as test points. A circuit diagram would have be good to have here.

Yeah; it's a bit strange to label a single MOSFET...

Breast cancer is a terrible disease, and I don't mean to be a downer but my BS detector is screaming on this one. I'd give the device image a pass if were just a journalist grabbing a stock PCB image, but that doesn't seem to be the case here. Anyone with even a trivial knowledge of electronics would be amused by the callouts. And all for just $5? After Theranos I guess I'm a bit sceptical of claims such as this.

Yeah, this looks like an Apple IIe logic board to me.

Commodity logic ICs ubiquitous and totally capable if needs are well-matched; it’s perhaps a deliberate prototype engineering/development choice.

Any FPGA could do the work smaller, faster, cheaper. So, I’m still skeptical.

From the paper:

> Synchronous voltage pulses are sent to both the electrode of the strip connecting to the gate and drain electrodes of the MOSFET. The drain pulse is applied for around 1.1 ms at a constant voltage. The gate pulse starts at 40 μs after the drain pulse and ends at 40 μs before the end of the drain pulse.

> the antigen-antibody complexes undergo stretching and contracting, akin to double springs, in response to a pulsed gate electric field. This motion across the antibody-antigen structure, corresponding to the pulse voltage applied on the test strip, induces an alteration in the protein's conformation, resulting in a time-dependent electric field applied to the MOSFET gate. Consequently, a springlike pattern emerges in the drain voltage waveform due to the external connection between the sensor strip and the MOSFET's gate electrode.

So they shake ‘em just so, and listen to the response…

ICs are perhaps variable timing & pulse-shaping logic?

There are a million people that could do this with a single FPGA in an afternoon. Why were none of them approached?

These are vacuum nerds more than electronics nerds. Most homebrew electronics designed by physicists for basic research are going to have these aesthetic qualities.

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