CDs to flexible biosensors: Researchers discover inexpensive recycling method | Hacker News Reader

CDs to flexible biosensors: Researchers discover inexpensive recycling method

binghamton.edu

Original paper:

https://www.nature.com/articles/s41467-022-31338-9

Figure 2 shows that the CD material is used kind of like electrodes or probes and those are attached to a microcontroller. This makes much more sense to me than the headline and main article.

Thanks, this is fascinating!

Verbatim archival gold CDs and the PI tape were purchased through Amazon for the UCDE fabrication illustrated in Fig. 1a and patterned with a Cricut Maker® fabric cutter.

The ECG MCU was designed with a uBIC-MZ24C20R (MEZOO, Inc, South Korea) chipset, which is a high-performance, low-powered one-chip 1 channel ECG (lead I) biometric sensor module with a 32-bit ARM Cortex-M0 processor. ECG data from two leads (RA and LA) were collected with 24-bit ADC resolution and 1 kHz sampling rate and then transmitted to a smartphone application in real-time via Bluetooth low-energy (BLE) communication.

AFAIK only (some) CD-Rs had a gold reflective layer, factory-pressed CDs use aluminum - so no gold, no silver. It's a bit strange that they started the whole project apparently without having a clue whether it would have actual practical value ("We used gold CDs, and we want to explore silver-based CDs, which I believe are more common.").

There are lots and lots of gold CDs out there. Sony, Verbatim, Kodak, etc all sold these "premium"/"gold"/"archival grade" versions. Even if its not billions like with aluminium, its definitly millions and a vast ressource to recycle. Sounds like a lot of practical value to me.

Most people (myself included) tend to think of a sensor as having some specific active measurement component. So a biologically available dissolved oxygen sensor (BOD) (for instance) has a semi permeable membrane, and an electrode, and measures the change in conductivity in the region due to dissolved oxygen changing the ability to pass volts through purified water. (ok, this was the 70s. I have no idea how they work now) The point is you pump volts across a gap, the membrane changes how they flow. Voila! dissolved oxygen changes the resistivity, you get to read how much dissolved oxygen was in the sample.

But, the word is also applicable to a passive device if it can pick up a signal which can then represent a modulation of some other thing, through RF. The tip of a logic/IC probe, or a portable volt-amp meter in this instance is what they are calling the "sensor" when in fact, the sensor is the increadibly finely balenced coil and spring and magnet: the probe is just how the data comes in. (ok this is the 1890s. I have no idea how this works now)

It's an antenna system. The Electrode gap, in my BOD example, but sans volts. You have to add the volts. Either it injects and reads, or its read-only. its the tip of the probe. Its got no active elements. How it "reads" depends on how you can convert something under measurement into a signal which it can pick up. The actual "sensor" component might be somewhere else. This is the transducer which you attach to something.

I am guessing it can be used to make RFID antenna as well. That would be cool. Does anyone remember the sparkle gaps you got for the back of AMPS cellphones which lit up like a christmas tree when the 'wake up' signal was pumped into the phone?

Actually nowadays, a dissolved oxy meter is probably best known as a fingerclip LED reader, and measures things by shining a red LED at your flesh to pick up on some aspect of the blood flow in a finger. I don't see any selectively permeable membrane there, its using another effect to measure. Passive probe? well.. you do shine an LED. so theres a transducer involved..

The pictures are pretty but surely a bunch of metallic squiggles doesn't make a sensor....... right?

> The flexible circuits then would be removed and stuck onto a person. With the help of a smartphone app, medical professionals or patients could get readings and track progress over time.

1) Draw a circle

2) Draw the rest of the owl

Indeed the pictures are not representative of the real setup. Anyway the idea is clever. The paper provides an overview about most of the missing bits, such as the mcu, power source, and software.

One of the applications is as an alternative electrode for ECG's. You'd attach a line from that sensor to an ECG machine (sorry, not an expert, so apologies for the imprecise terminology) and get similar results to using commercial electrodes.

I dunno if that makes it a sensor, technically, or just one component in a more complex sensor apparatus.

Why not just buy gold leaf? It's about the same price, and you know what you're getting.

Yup, I was looking at the 20-30 minute production time, and thought, per sensor, that just doesn't work.

I bought edible gold sheets to build gold electrodes on a bit of sticky tape. Worked well enough for our experiments in EEG.

Is that $1.50 per device from the conversion process or extra materials? I remember getting stacks of 50 CDs for like $5.

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