Schematic diagram of the touch-sensitive skin. (Credit: Haofeng Chen et al., ArXiv, 2026)
Hypoesthesia, more commonly referred to as numbness, is one of the more distressing ailments that can affect us humans, primarily because it reminds us of just how much we rely on our sensation of touch in daily life. From experiencing the world around us, handling objects, noticing when you just bumped into that side table again and the comforting hug of a fellow human being, touch is perhaps the most important of our senses.
There are quite a few rather unconventional methods of propulsion, but perhaps one of the more curious approaches involved Helmholtz resonance, as demonstrated by [Junsun Hwang] et al. with a paper in Science Advances and associated summary article by EPFL’s School of Engineering.
Although probably better known from something like musical instruments, Helmholtz resonance can be used for more than creating or deadening noise. If stimulated with an external acoustic source that matches the chamber’s resonance frequency the result is a jet of air at the neck of the chamber. This acoustic actuation can thus be used for a number of applications.
In the paper a number of such applications are demonstrated, including a boat with three of these chambers for propulsion and steering, as well as a microflier (see above image) that when placed above an ultrasonic phased area will hover due to the production of this jet of air.
This microflier concept was then adapted with angled resonator chambers so that they could drive a propeller. Naturally, the produced thrust is only a fraction of a Newton so it’s essential to make these structures as light as possible, in the order of micrograms. These microfliers were created using high-resolution 3D printing, with a few iterations attempted to determine the optimal configuration.
In the case of the boat the ultrasonic transducers were directly placed on the bottom of the resonance chamber, but in the case of the microfliers the weight limitations necessitate these transducers to be external. Even if not the most practical kind of flying robot, as a demonstrator of this application of Helmholtz resonance for acoustic propulsion it’s pretty cool.
Unlike biological systems, which can use muscles, robots that try to imitate them don’t have particularly fast, powerful, compact linear actuators available. This puts walking robots at a particular disadvantage, since they can’t spread their actuators along a limb and have to place them right at the joint. [Food for Robots] took on the challenge of building such a joint-mounted actuator, and shared the results in a recent video.
[Food for Robots] is building a walking robot, so he needed a compact, lightweight, and backdrivable actuator capable of producing 20 Newton-meters of torque. He’d previously built a largely 3D-printed actuator, but when he tried to exceed 10 Nm of torque with it, various parts kept breaking. He therefore machined the second iteration out of aluminum; since it didn’t need to be 3D printed, he switched from a Capstan drive to a planetary gearbox. The gearbox sits in the center of the actuator, inside the stator, and uses several stacked layers of gears to increase strength within the limits of a small CNC.
Remember Animusic? They were these incredible animated music videos with original tunes being played by computer-generated robots. Well, the MegCell Pulse might be the coolest robots-playing-music thing we’ve seen since Animusic.
Built by [Bruce] over six years’ time, this futuristic wonder features two robots working in concert to play acoustic guitar, just like a pair of human hands would. You just feed them digital tablature, and off go the fraternal twins, with one doing the fretting, and the other doing the plucking via six individual plectrum. It’s digital music producing analog sound from a physical instrument.
How does MegCell Pulse work? It’s essentially a system of gears, magnetic actuators, and arms, contained in a 3D-printed structure. The only real limitations are that it can’t traverse the entire fretboard, nor can it slide between frets. That said, you can absolutely buy one for your own guitar via [Bruce]’s modestly-goaled Kickstarter.
The kicker here is that you can’t buy an assembled MegCell Pulse; you must print and build it yourself. Back on the upside, the most expensive supporting tier is a mere $100. For that price, you get the complete digital plans. That includes 3D print files, an assembly guide, the control software, and a parts list. Be sure to check out the demo videos embedded after the break.
With the massive steam explosion that shredded the #4 RBMK reactor at the Chernobyl Nuclear Power Plant in 1986 it suddenly made robots that could survive a high ionizing radiation environment into the hottest item on the planet. Over the course of forty years many generations of such robots were developed, tested, improved upon or discarded, all to explore and handle hazardous waste throughout the depths of the #4 reactor’s remains.
Researchers of the ISP NPP next to one of the TR robots. (Credit: ISP NPP)
Even if the entire development and decisions here would easily fit a couple of feature length movies, the recent documentary by the [Chornobyl Family] provides a solid overview of the engineering challenges, the issues encountered along the way and the forced evolution of initially very basic designs into the robotics that today trundle and wriggle around inside reactor #4, as well as their cousins over at the couple of stricken reactors at Japan’s Fukushima Daiichi power station.
Unlike the other robots developed from 1986 onwards to provide general clean-up of scattered core material outside of the core, these robots had to venture deep inside, where radiation levels were the highest and correspondingly the challenges much more severe. This was such a problem that initially it were humans who did the exploration, as robots proved to be too fragile and too prone to getting stuck.
Until the 1990s exploration of the ruined core was quite limited, also because of a lack of urgency. While the outside clean-up and construction of the sarcophagus had to be done as quickly as possible, the core exploration was more slow and methodical, based around trying to establish its condition, what core material remained inside and try to take samples of interesting objects like the well-known ‘elephant’s foot’.
As someone who disassembles and repairs hardware, [Aad] eventually ended up with a huge collection of mixed bolts and screws. This led to creating the automatic bolt and screw sorting system you see here, although in a way it is just a proof of concept. Bolts and screws happen to be a useful application for now, but the system is capable of sorting just about any small objects.
A bit of machine vision detects the size and shape of each object. Weight can also be measured.
Mixed pieces go onto a large conveyor belt, shown on the right. This feeds a few screws at a time down a chute, where they roll onto an illuminated platform.
Above the lit platform is a camera, and machine vision is used to detect the size and shape and orientation of each screw. A robotic gripper on a gantry picks the screws up one by one — separating them first if they happened to clump together — and places each in a drop-off cart. The cart drops the object into a receptacle with its brethren, making sure similar ones are grouped together. Watch it in action in the video, embedded below the page break.
It’s a great build that shows fancy components aren’t necessary for good results. Servos and steppers are controlled with an ESP32-WROOM board, and a piezo sensor detects screws falling off the conveyor. Some of you may have noticed a repurposed Ultimaker 3D printer serving as the bulk of the system, its hot end having been replaced with a gripper that can raise and lower. The overhead camera is an ESP32-CAM adapted to accept M12 lenses so it can focus on the platform.
There’s one more feature worth mentioning — the system also has the ability to measure the weight of a picked object by placing it onto a moveable inspection platform, which can optionally put it under a USB microscope for a closer look. Everything is controlled by a nearby PC, so there’s a lot of flexibility built into the system.
We suppose that once all the screws and bolts in a shop are sorted, it only makes sense to sort all the nuts. Are there other objects besides screws and bolts that would be useful to sort with a system like this? If you have any ideas, don’t keep them to yourself! [Aad] would love to hear your comments and ideas, so share them below.
When the Chernobyl Nuclear Power Plant’s #4 reactor experienced an extreme criticality event on that infamous day in 1986, the resulting steam explosion and lack of any kind of containment building meant that parts of the core were scattered throughout the site. In an extensive update to the original 2023 video, the [Chornobyl Family] covers the mad scramble to design robots to perform on-the-ground measurements, and ultimately remove all this debris for safe disposal.
The TR-1A, an early debris removal robot. (Source: Chornobyl Family, YouTube)
This essentially took the form of a hackathon, involving teams from all over the USSR and allied nations, creating the most diverse range of robots that 1980s Soviet technology and later Western technology could muster.
Many of these robots didn’t perform very well, or at all, mostly due to the bypassing of any kind of testing before deployment. Especially at the beginning of the clean-up the robots were being pushed into the high-radiation zones as soon as they were finished, with not only mechanical issues being a problem, but also with e.g. inaccurate radiation measurements by the RR-1 robot, that overstated measurements by more than a factor of ten. Meanwhile the RR-2 and RR-3 were too top-heavy and after deployment by helicopter simply tipped over. Eventually manual measurements proved to be faster and safer.
Early debris removal robots like the TR-1A were rather simplistic, with successive generations of robots over the next weeks and months improving on it. The use of a combustion engine instead of batteries provided to be a boon, as combustion engines are far less affected by radiation.
The BAER Beloyarets used an airport cart as the basis, with its electronics relying on vacuum tube technology and relays, with an internal combustion engine. This proved to be one of the most reliable designs and it’s been largely preserved on display in the Chornobyl Exclusion Zone, with many others of these robots also being on display around the nuclear plant or in the city of Chornobyl.
Overall an absolutely dizzying number of robotic designs were invented on the spot, adapted from existing designs or repurposed for operation in a high-radiation zone. Eventually bulldozer designs like the STR-1 helped to push radioactive debris off the roofs into containers, massively reducing the radioactive contamination of the area.
The fact that following #4’s RUD the other three RBMK units were able to keep operating safely without risks to its operators, and with the zone now safe for tourists, is a real testament to the success of the worst hackathon imaginable. Many of the lessons learned are relevant today, including during the decommissioning of Fukushima Daiichi’s melted-down cores.
