Noninvasive Sensors For Brain–Machine Interfaces Based On Micropatterned Epitaxial Graphene

April 15, 2023 by Maya Posch 4 Comments

As fun as brain-computer interfaces (BCI) are, for the best results they tend to come with the major asterisk of requiring the cutting and lifting of a section of the skull in order to implant a Utah array or similar electrode system. A non-invasive alternative consists out of electrodes which are placed on the skin, yet at a reduced resolution. These electrodes are the subject of a recent experiment by [Shaikh Nayeem Faisal] and colleagues in ACS Applied NanoMaterials employing graphene-coated electrodes in an attempt to optimize their performance.

Impedance values of eight-channel FEG and eight-channel HPEG sensor systems placed on the occipital area of the head. (Faisal et al., 2023)

Although external electrodes can be acceptable for basic tasks, such as registering a response to a specific (visual) impulse or for EEG recordings, they can be impractical in general use. Much of this is due to the disadvantages of the ‘wet’ and ‘dry’ varieties, which as the name suggests involve an electrically conductive gel with the former.

This gel ensures solid contact and a resistance of no more than 5 – 30 kΩ at 50 Hz, whereas dry sensors perform rather poorly at >200 kΩ at 50 Hz with worse signal-to-noise characteristics, even before adding in issues such as using the sensor on a hairy scalp, as tends to be the case for most human subjects.

In this study, they created electrode arrays in a number of configurations, each of which used graphene as the interface material. The goal was to get a signal even through human hair — such as on the back of the head near the visual cortex — that would be on-par with wet electrodes. The researchers got very promising results with hex-patterned epitaxial graphene (HEPG) sensors, and even in this early prototype stage, the technique could offer an alternative where wet electrodes are not an option.

While the subject is complex, brain-computer interfaces don’t have to be the sole domain of research laboratories. We recently covered an open hardware Raspberry Pi add-on that can let you experiment with detecting and filtering biosignals from the comfort of your own home.

Sufficiently Advanced Tech: Has Bugs

April 15, 2023 by Elliot Williams 74 Comments

Arthur C. Clarke said that “Any sufficiently advanced technology is indistinguishable from magic”. He was a sci-fi writer, though, and not a security guy. Maybe it should read “Any sufficiently advanced tech has security flaws”. Because this is the story of breaking into a car through its headlight.

In a marvelous writeup, half-story, half CAN-bus masterclass, [Ken Tindell] details how car thieves pried off the front headlight of a friend’s Toyota, and managed to steal it just by saying the right things into the network. Since the headlight is on the same network as the door locks, pulling out the bulb and sending the “open the door” message repeatedly, along with a lot of other commands to essentially jam some other security features, can pull it off.

Half of you are asking what this has to do with Arthur C. Clarke, and the other half are probably asking what a lightbulb is doing on a car’s data network. In principle, it’s a great idea to have all of the electronics in a car be smart electronics, reporting their status back to the central computer. It’s how we know when our lights are out, or what our tire pressure is, from the driver’s seat. But adding features adds attack surfaces. What seems like magic to the driver looks like a gold mine to the attacker, or to car thieves.

With automotive CAN, security was kind of a second thought, and I don’t mean this uncharitably. The first goal was making sure that the system worked across all auto manufacturers and parts suppliers, and that’s tricky enough. Security would have to come second. And more modern cars have their CAN networks encrypted now, adding layers of magic on top of magic.

But I’m nearly certain that, when deciding to replace the simple current-sensing test of whether a bulb was burnt out, the engineers probably didn’t have the full cost of moving the bulb onto the CAN bus in mind. They certainly had dreams of simplifying the wiring harness, and of bringing the lowly headlight into the modern age, but I’d bet they had no idea that folks were going to use the headlight port to open the doors. Sufficiently advanced tech.

Better Laser Cuts: Know Your Kerf

April 15, 2023 by Al Williams 19 Comments

The recent crop of laser cutters are nothing short of miraculous. For a few hundred dollars you can get a machine that can easily engrave and — subject to materials — cut well, too. [Nate] has been taking advantage of a laser to make boxes that join together using finger joinery. The problem is, the pieces have to fit exactly to get a good box. While setting dimensions in software is fine, you need to account for how much material the laser removes — something traditional woodworkers and machinists know as kerf.

You can, of course, employ trial and error to get good results. But that’s wasteful and potentially time-consuming. [Nate] built a “tolerance fence” that is quick to cut out and allows accurate measurement of kerf. You can quickly use the tolerance fence to make measurements and increase your chances of nailing your boxes on the first cut.

You have to customize the fence based on the thickness of your material. [Nate] uses Lightburn, which probably has a kerf offset already set by default in your layers. If not, you’ll need to turn it on and set an estimate of your kerf size. Then you are ready to cut the fence pieces and see how they fit together.

If the fit is too loose, you want to raise the kerf setting and try again. If it is too tight, you lower the kerf setting. As [Nate] says, “Lower equals looser.”

The results speak for themselves, as you can see in the treasure chest image [Nate] provided. Well worth the effort to get this parameter right. We do enjoy laser cutting and engraving things. If you are cutting and don’t have air assist, you really need to hack up something.

Uranium-241 Isotope Created And Examined Via Multinucleon Transfer Reactions And Mass Spectrometry

April 15, 2023 by Maya Posch 11 Comments

A recent paper (PDF) in Physical Review Letters by T. Niwase and colleagues covers a fascinating new way to both create and effectively examine isotopes by employing a cyclotron and a mass spectrograph. In the paper, they describe the process of multinucleon transfer (MNT) and analysis at the recently commissioned KEK Isotope Separation System (KISS), located at the RIKEN Nishina Center in Japan.

Sketch of the KISS experimental setup. The blue- and yellow-colored areas are filled with Ar and He gases, respectively. Differential pumping systems are located after the doughnut-shaped gas cell as well as before and after the GCCB. (Credit: Niwase et al., 2023) — Sketch of the KISS experimental setup. The blue- and
yellow-colored areas are filled with Ar and He gases, respectively. Differential pumping systems are located after the doughnut-shaped gas cell as well as before and after the GCCB. (Credit: Niwase et al., 2023)

The basic process which involves the RIKEN Ring Cyclotron, which was loaded for this particular experiment with Uranium-238 isotope. Over the course of four days, ²³⁸U particles impinged on a ¹⁹⁸Pt target, after which the resulting projectile-like fragments (PLF) were led through the separation system (see sketch). This prepared the thus created ions to be injected into the multi-reflection time-of-flight mass spectrograph (MRTOF MS), which is a newly installed and highly refined mass spectrograph which was also recently installed at the facility.

Using this method, the researchers were able to establish that during the MNT process in the cyclotron, the transfer of nucleons from the collisions had resulted in the production of ²⁴¹U as well as ²⁴²U. Although the former had not previously been produced in an experimental setting, the mass of ²⁴²U had not been accurately determined. During this experiment, the two uranium as well as neptunium and other isotopes were led through the MRTOF MS instrument, allowing for the accurate measurement of the characteristics of each isotope.

The relevance of producing new artificial isotopes of uranium lies not so much in the production of these, but rather in how producing these atoms allows us to experimentally confirm theoretical predictions and extrapolations from previous data. This may one day lead us to amazing discoveries such as the famously predicted island of stability, with superheavy, stable elements with as of yet unknown properties.

Even if such astounding discoveries are not in the future for theoretical particle physics, merely having another great tool like MNT to ease the burden of experimental verification would seem to be more than worth it.

Kicad Autorouting Made Easy

April 14, 2023 by Al Williams 23 Comments

One of the most laborious tasks in PCB layout is the routing. Autorouting isn’t always perfect, but it is nice to have the option, even if you only use it to get started and then hand-tune the resulting board. Unfortunately, recent versions of Kicad have dropped support for autorouting. You can, however, still use Freerouting and the video from [Mr. T] below shows you how to get started.

There are three ways to get the autorouting support. You can install Java and a plugin, you can isntall using a ZIP file, or you can simply export a Specctra DSN file and use Freerouting as a standalone program. Then you import the output DSN file, and you are done.

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Need To Pick Objects Out Of Images? Segment Anything Does Exactly That

April 14, 2023 by Donald Papp 7 Comments

Segment Anything, recently released by Facebook Research, does something that most people who have dabbled in computer vision have found daunting: reliably figure out which pixels in an image belong to an object. Making that easier is the goal of the Segment Anything Model (SAM), just released under the Apache 2.0 license.

The online demo has a bank of examples, but also works with uploaded images.

The results look fantastic, and there’s an interactive demo available where you can play with the different ways SAM works. One can pick out objects by pointing and clicking on an image, or images can be automatically segmented. It’s frankly very impressive to see SAM make masking out the different objects in an image look so effortless. What makes this possible is machine learning, and part of that is the fact that the model behind the system has been trained on a huge dataset of high-quality images and masks, making it very effective at what it does.

Continue reading “Need To Pick Objects Out Of Images? Segment Anything Does Exactly That” →

Building An Electron Microscope For Research

April 14, 2023 by Bryan Cockfield 10 Comments

There are a lot of situations where a research group may turn to an electron microscope to get information about whatever system they might be studying. Assessing the structure of a virus or protein, analyzing the morphology of a new nanoparticle, or examining the layout of a semiconductor all might require the use of one of these devices. But if your research involves the electron microscope itself, you might be a little more reluctant to tear down these expensive devices to take a look behind the curtain as the costs to do this for more than a few could quickly get out of hand. That’s why this research group has created their own electron detector.

Specifically, the electron detector is designed for use in a scanning electron microscope, which is typically used for inspecting the surface of a sample and retrieving a high-resolution, 3D image of it compared to transmission microscopes which can probe internal structures. The detector is built on a four-layer PCB which includes the photodiode sensing array, a series of amplifiers, and a power supply. All of the circuit diagrams and schematics are available for inspection as well thanks to the design being licensed under the open Creative Commons license. For any research team looking to build this, a bill of materials is also included, as is a set of build instructions.

While this is only one piece of the puzzle surrounding the setup and operation of an electron microscope, its arguably the most important, and also greatly lowers the barrier of entry for anyone looking to analyze electron microscope design themselves. With an open standard, anyone is free to modify or augment this design as they see fit which is a marked improvement over the closed and expensive proprietary microscopes out there. And, if low-cost microscopes are your thing be sure to check out this fluorescence microscope we featured that uses readily-available parts to dramatically lower the cost compared to commercial offerings.