A glass plate holds a translucent set of silver electrodes. The plate appears to be suspended across two petri dishes, so the scale must be small.

Hydrogels For Bioelectronic Interfaces

Interfacing biological and electrical systems has traditionally been done with metal electrodes, but something flexible can be more biocompatible. One possible option is 3D-printed bioelectric hydrogels.

Electrically conductive hydrogels based on conducting polymers have mechanical, electrical, and chemical stability properties in a fully organic package that makes them more biocompatible than other systems using metals, ionic salts, or carbon nanomaterials. Researchers have now found a way to formulate bi-continuous conducting polymer hydrogels (BC-CPH) that are a phase-separated system that can be used in a variety of manufacturing techniques including 3D printing.

To make the BC-CPH, a PEDOT:PSS electrical phase and a hydrophilic polyurethane mechanical phase are mixed with an ethanol/water solvent. Since the phase separation occurs in the ink before deposition, when the solvent is evaporated, the two phases remain continuous and interspersed, allowing for high mechanical stability and high electrical conductivity which had previously been properties at odds with each other. This opens up new avenues for printed all-hydrogel bioelectronic interfaces that are more robust and biocompatible than what is currently available.

If you want to try another kind of squishy electrode gel, try growing it.

Ecological System Dynamics For Computing

Some of you may remember that the ship’s computer on Star Trek: Voyager contained bioneural gel packs. Researchers have taken us one step closer to a biocomputing future with a study on the potential of ecological systems for computing.

Neural networks are a big deal in the world of machine learning, and it turns out that ecological dynamics exhibit many of the same properties. Reservoir Computing (RC) is a special type of Recurrent Neural Network (RNN) that feeds inputs into a fixed-dynamics reservoir black box with training only occurring on the outputs, drastically reducing the computational requirements of the system. With some research now embodying these reservoirs into physical objects like robot arms, the researchers wanted to see if biological systems could be used as computing resources.

Using both simulated and real bacterial populations (Tetrahymena thermophila) to respond to temperature stimuli, the researchers showed that ecological system dynamics has the “necessary conditions for computing (e.g. synchronized dynamics in response to the same input sequences) and can make near-future predictions of empirical time series.” Performance is currently lower than other forms of RC, but the researchers believe this will open up an exciting new area of research.

If you’re interested in some other experiments in biocomputing, checkout these RNA-based logic gates, this DNA-based calculator, or this fourteen-legged state machine.

Spaying Cats In One Shot

Feral cats live a rough life, and programs like Trap, Neuter, Release (TNR) attempt to keep their populations from exploding in a humane way. Researchers in Massachusetts have found a non-surgical way to spay cats that will help these efforts.

A single dose of anti-Müllerian hormone (AMH) gene therapy suppresses ovarian follicle formation, essentially turning off the ovulation cycle. After following the test cats for two years, none had kittens, unlike the cats in the control group. Other major hormones like estrogen were unaffected in the cats and they didn’t exhibit any negative side effects. The researchers said it will be some time before the treatment can be widely deployed, but it offers hope for helping our internet overlords and the environs they terrorize inhabit.

For those of you doing TNR work, you might want to try this trap alert system to let you know you’ve caught a cat for spaying or neutering. If you’d rather use a cat treat dispenser to motivate your code monkeys, then check out this hack.

A clear flexible PCB with a number of gold electrodes on one end. It is wrapped over a black cable to demonstrate its flexibility. A set of dashed white lines goes from one end to a zoomed in image of the circuit structure inset in the top right of the image.

Biohybrid Implant Patches Broken Nerves With Stem Cells

Neural interfaces have made great strides in recent years, but still suffer from poor longevity and resolution. Researchers at the University of Cambridge have developed a biohybrid implant to improve the situation.

As we’ve seen before, interfacing electronics and biological systems is no simple feat. Bodies tend to reject foreign objects, and transplanted nerves can have difficulty assuming new roles. By combining flexible electronics and induced pluripotent stem cells into a single device, the researchers were able to develop a high resolution neural interface that can selectively bind to different neuron types which may allow for better separation of sensation and motor signals in future prostheses.

As is typically the case with new research, the only patients to benefit so far are rats and only on the timescale of the study (28 days). That said, this is a promising step forward for regenerative neurology.

We’re no strangers to bioengineering here. Checkout how you can heal faster with electronic bandages or build a DIY vibrotactile stimulator for Coordinated Reset Stimulation (CRS).

(via Interesting Engineering)

A clear droplet sits on a blue PCB with gold traces. A syringe with a drop of clear liquid sits above the droplet.

Grow Your Own Brain Electrodes

Bioelectronics has been making great strides in recent years, but interfacing rigid electrical components with biological systems that are anything but can prove tricky. Researchers at the Laboratory for Organic Electronics (LOE) have found a way to bridge the gap with conductive gels. (via Linköping University)

Outside the body, these gels are non-conductive, but when injected into a living animal, the combination of gel and the body’s metabolites creates a conductive electrode that can move with the tissue. This is accompanied by a nifty change in color which makes it easy for researchers to see if the electrode has formed properly.

Side-by-side images of a zebrafish tail. Both say "Injected gel with LOx:HRP" at the top with an arrow going to the upper part of the tail structure. The left says "t=0 min" and "Injected with gel GOx:HRP" along the bottom with an arrow going to the lower part of the tail structure. The tail shows darkening in the later image due to formation of bioelectrodes.

Applications for the technology include better biological sensors and enhanced capabilities for future brain-controlled interfaces. The study was done on zebrafish and medicinal leeches, so it will be awhile before you can pick up a syringe of this stuff at your local computer store, but it still offers a tantalizing glimpse of the future.

We’ve covered a few different brain electrodes here before including MIT’s 3D printed version and stentrodes.

The Blue Soup Saga Is One Beefy Mystery

Beef soup! You’d normally expect it to be somewhere from reddish-brown to grey, depending on how well it was cooked and prepared. However, strangely, an assistant professor found the beef soup in their fridge had mysteriously turned blue. That spawned an investigation into the cause which is still ongoing.

[Dr. Elinne Becket] has earned her stripes in microbiology, but the blue soup astounded her. Despite her years of experience, she was unable to guess at the process or a source of contamination that could turn the soup blue. Indeed, very few natural foods are blue at all. Even blueberries themselves are more of a purple color. The case sparked enough interest that [Elinne] went back to the trash to collect photos and sample for research at the request of others.

Thus far, metagenomic DNA analysis is ongoing and samples of the soup have been cultivated in petri dishes. Early analysis shows that some of the microbes form iridescent colonies, Another researcher is trying to determine if the bugs from the soup can make blue color appear on soft cheese. There’s some suspicion that a bacteria known as pseudomonas aeruginosa could be the cause of the blue color, but that presents its own problems. P. aeruginosa is classified as a Biosafety Level 2 pathogen which would require some researchers to abandon work on the project for safety reasons.

The jury’s still out on this microbiological mystery. If you’ve got some ideas on what could be going on, let us know in the comments!

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Hackaday Links: December 18, 2022

By now everyone has probably seen the devastation wrought by the structural failure of what was once the world’s largest free-standing cylindrical aquarium. The scale of the tank, which until about 5:50 AM Berlin time on Friday graced the lobby of the Raddison Blu hotel, was amazing — 16 meters tall, 12 meters in diameter, holding a million liters of saltwater and some 1,500 tropical fish. The tank sat atop a bar in the hotel lobby and was so big that it even had an elevator passing up through the middle of it.

But for some reason, the tank failed catastrophically, emptying its contents into the hotel lobby and spilling the hapless fish out into the freezing streets of Berlin. No humans were killed by the flood, which is miraculous when you consider the forces that were unleashed here. Given the level of destruction, the displaced hotel guests, and the fact that a €13 million structure just up and failed, we’re pretty sure there will be a thorough analysis of the incident. We’re pretty interested in why structures fail, so we’ll be looking forward to finding out the story here.

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