Hackaday Prize 2023: Finger Tracking Via Muscle Sensors

Whether you want to build a computer interface device, or control a prosthetic hand, having some idea of a user’s finger movements can be useful. The OpenMuscle finger tracking sensor can offer the data you need, and it’s a device you can readily build in your own workshop.

The device consists of a wrist cuff that mounts twelve pressure sensors, arranged radially about the forearm. The pressure sensors are a custom design, using magnets, hall effect senors, and springs to detect the motion of the muscles in the vicinity of the wrist.

We first looked at this project last year, and since then, it’s advanced in leaps and bounds. The basic data from the pressure sensors now feeds into a trained machine learning model, which then predicts the user’s actual finger movements. The long-term goal is to create a device that can control prosthetic hands based on muscle contractions in the forearm. Ideally, this would be super-intuitive to use, requiring a minimum of practice and training for the end user.

It’s great to see machine learning combined with innovative mechanical design to serve a real need. We can’t wait to see where the OpenMuscle project goes next.

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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 cinematic shot of the resulting prosthetic finger attached to the glove

Missing Finger Gets A Simple Yet Fancy Replacement

The possibility of a table saw accident is low, but never zero — and [Nerdforge] has lost a finger to this ever-useful but dangerous contraption. For a right-handed person, losing the left hand pinky might not sound like much, but the incident involved some nerve damage as well, making inaccessible a range of everyday motions we take for granted. For instance, holding a smartphone or a pile of small objects without dropping them. As a hacker, [Nerdforge] decided to investigate just how much she could do about it.

On Thingiverse, she’s hit a jackpot: a parametric prosthetic finger project by [Nicholas Brookins], and in no time, printed the first version in resin. The mechanics of the project are impressive in their simplicity — when you close your hand, the finger closes too. Meant to be as simple as possible, this project only requires a wrist mount and some fishing line. From there, what could she improve upon? Aside from some test fits, the new finger could use a better mounting system, it could stand looking better, and of course, it could use some lights.

For a start, [Nerdforge] redesigned the mount so that the finger would instead fasten onto a newly-fingerless glove, with a few plastic parts attached into that. Those plastic parts turned out to be a perfect spot for a CR2032 battery holder and a microswitch, wired up to a piece of LED filament inserted into the tip of the finger. As for the looks, some metal-finish paint was found to work wonders – moving the glove’s exterior from the “printed project” territory into the “futuristic movie prop” area.

The finger turned out to be a resounding success, restoring the ability to hold small objects in ways that the accident made cumbersome. It doesn’t provide much in terms of mechanical strength, but it wasn’t meant to do that. Now, [Nerdforge] has hacked back some of her hand’s features, and we have yet another success story for all the finger-deficient hackers among us. Hacker-built prosthetics have been a staple of Hackaday, with the OpenBionics project in particular being a highlight of 2015 Hackaday Prize — an endearing demonstration of hackers’ resilience.

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A man with dark skin in a red shirt and khaki shorts sits in a chair. His left leg has a prosthetic below the knee. The upper half of the prosthethic is an off white plastic socket with flecks of different off white plastic throughout hinting at the recycled nature of the plastic. The lower half is a metal tube attached to an artificial foot in black sandals.

Precious Plastic Prosthetics

Plastic waste is a major problem, but what if you could turn the world’s trash into treasure? [Yayasan Kaki Kita Sukasada (YKKS)] in Indonesia is doing this by using recycled plastic to make prosthetic legs.

Polypropylene source material is shredded and formed into a sheet which is molded into the required shape for the socket. A layer of cloth and foam is used to cushion the interface between the patient and the socket itself. Using waste plastic to make parts for the prosthetics lowers the price for patients as well as helps to keep this material out of the landfill.

What makes this project really exciting is that [YKKS] employs disabled people who develop the prosthetics and also trains patients on how to maintain and repair their prosthetics with easily sourced tools and materials. With some medical device companies abandoning their devices, this is certainly a welcome difference.

We’ve previously covered the Precious Plastic machines used to make the plastic sheets and the organization’s developments at small scale injection molding.

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A prosthetic eye anodized green around the edges with a yellow and blue "iris" surrounding an LED center.

Skull Lamp Illuminates The Cyberpunk Future

Cyberpunk is full of characters with cool body mods, and [bsmachinist] has made a prosthetic eye flashlight (TikTok) that is both useful and looks futuristic. [via Reddit]

[bsmachinist] has been machining titanium prosthetic eyes for over five years now, and this latest iteration, the Skull Lamp, has a high brightness LED that he says is great for reading books at night as well as any other task you might have for a headlamp. Battery life is reported as being 20 hours, and the device is switched by passing a magnet (Instagram) near the prosthetic.

We love seeing how prosthetics have advanced in the last few years with the proliferation of advanced tools for makers. Some other interesting prosthetics we’ve covered are this DIY Socket for Prosthetics with a built-in charger and power supply and several different prosthetic projects for kids including these Heroic Prosthetics by Open Bionics, the E-Nable Alliance, and a Kid Who Designed his Own Prosthetic.

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Hackaday Links: October 23, 2022

There were strange doings this week as Dallas-Forth Worth Airport in Texas experienced two consecutive days of GPS outages. The problem first cropped up on the 17th, as the Federal Aviation Administration sent out an automated notice that GPS reception was “unreliable” within 40 nautical miles of DFW, an area that includes at least ten other airports. One runway at DFW, runway 35R, was actually closed for a while because of the anomaly. According to GPSjam.org — because of course someone built a global mapping app to track GPS coverage — the outage only got worse the next day, both spreading geographically and worsening in some areas. Some have noted that the area of the outage abuts Fort Hood, one of the largest military installations in the country, but there doesn’t appear to be any connection to military operations. The outage ended abruptly at around 11:00 PM local time on the 19th, and there’s still no word about what caused it. Loss of GPS isn’t exactly a “game over” problem for modern aviation, but it certainly is a problem, and at the very least it points out how easy the system is to break, either accidentally or intentionally.

In other air travel news, almost as quickly as Lufthansa appeared to ban the use of Apple AirTags in checked baggage, the airline reversed course on the decision. The original decision was supposed to have been based on “an abundance of caution” regarding the potential for disaster from its low-power transmitters, or should a stowed AirTag’s CR2032 battery explode. But as it turns out, the Luftfahrt-Bundesamt, the German civil aviation authority, agreed with the company’s further assessment that the tags pose little risk, green-lighting their return to the cargo compartment. What luck! The original ban totally didn’t have anything to do with the fact that passengers were shaming Lufthansa online by tracking their bags with AirTags while the company claimed they couldn’t locate them, and the sudden reversal is unrelated to the bad taste this left in passengers’ mouths. Of course, the reversal only opened the door to more adventures in AirTag luggage tracking, so that’s fun.

Energy prices are much on everyone’s mind these days, but the scale of the problem is somewhat a matter of perspective. Take, for instance, the European Organization for Nuclear Research (CERN), which runs a little thing known as the Large Hadron Collider, a 27-kilometer-long machine that smashes atoms together to delve into the mysteries of physics. In an average year, CERN uses 1.3 terawatt-hours of electricity to run the LHC and its associated equipment. Technically, this is what’s known as a hell of a lot of electricity, and given the current energy issues in Europe, CERN has agreed to shut down the LHC a bit early this year, shutting down in late November instead of the usual mid-December halt. What’s more, CERN has agreed to reduce usage by 20% next year, which will increase scientific competition for beamtime on the LHC. There’s only so much CERN can do to reduce the LHC’s usage, though — the cryogenic plant to cool the superconducting magnets draws a whopping 27 megawatts, and has to be kept going to prevent the magnets from quenching.

And finally, as if the COVID-19 pandemic hasn’t been weird enough, the fact that it has left in its wake survivors whose sense of smell is compromised is alarming. Our daily ritual during the height of the pandemic was to open up a jar of peanut butter and take a whiff, figuring that even the slightest attenuation of the smell would serve as an early warning system for symptom onset. Thankfully, the alarm hasn’t been tripped, but we know more than a few people who now suffer from what appears to be permanent anosmia. It’s no joke — losing one’s sense of smell can be downright dangerous; think “gas leak” or “spoiled food.” So it was with interest that we spied an article about a neuroprosthetic nose that might one day let the nasally challenged smell again. The idea is to use an array of chemical sensors to stimulate an array of electrodes implanted near the olfactory bulb. It’s an interesting idea, and the article provides a lot of fascinating details on how the olfactory sense actually works.

Forearm Muscle Contraction Sensor Is Useful Component For Open Source Prosthetics

Being able to actuate parts of a prosthetic limb can make it much more useful. To help in this goal for partial arm or hand amputees, [TURFPTAx] has developed a sensor for detecting forearm muscle contractions. 

The sensor itself is cost-effective and simple to build.

The build is part of the Open Prosthetics project, which aims to offer open designs for various types of prosthetic devices. It apes common commercial designs using a simple electromechanical system.

The build relies on magnets mounted on twelve pistons that move when the muscles contract under the skin. The pistons are sprung to allow them to follow the expansion and contractions of the muscles, and the motion of the magnets is detected by hall effect sensors. The system is bulkier than some other solutions, but has the benefit of clean output and the ability to detect the movement of several distinct muscle groups. The data is all collected by an ESP32 which is then sent wirelessly to a computer for measurement, with [TURFPTAx] using the PyGame library to plot the sensor data.

[TURFPTAx] notes that the output of the sensors would be perfect to input into a machine learning system. Video after the break.

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