flex PCB

20 Articles

Supercon 2022: Samy Kamkar’s Glowing Breath

January 10, 2023 by 6 Comments

Sometimes the journey itself is the destination. This one started when [Samy] was 10 and his mom bought a computer. He logged on to IRC to talk with people about the X-Files and was WinNuked. Because of that experience, modulo a life of hacking and poking and playing, the talk ends with a wearable flex-PCB Tesla coil driving essentially a neon sign made from an ampule of [Samy]’s own breath around his neck. Got that? Buckle up, it’s a rollercoaster.

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Sticker Brings The Heat

February 13, 2022 by 17 Comments

[Carl] is always looking at making heater plates for PCB reflow and other applications. In his latest video, he shows how he is using thin flexible PCBs with adhesive backs as stickers that get hot. You can find gerber files and design files on GitHub.

You might think that this is a pretty simple thing to do with a flex PCB, but it turns out while the PCB might be flexible, the traces aren’t and so the typical long traces you see in a heater won’t allow the sticker to bend, which is a problem if you want to wrap it around, say, a coffee mug.

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Dreaming Of A Transparent (PCB) Christmas

January 26, 2021 by 1 Comment

[Carl] wanted to put his force sensors on a transparent PCB and had to ask his board vendor for a special sample. Flexible PCBs are available on transparent substrates made of PET, but they are not as common as polyimide boards. As [Carl] found out, these boards are a bit thicker, a bit less flexible, and don’t hold up to very high heat as well as the standard boards. Undeterred, he designed a 3D Christmas tree using the clear boards. The result that you can see in the video below looks pretty good and would have been hard to duplicate with conventional means.

When you build the board it is as a flat spiral, but lifting it in the center allows it to expand into a conical tree shape. The circuit itself is just an LED blinker, but the flexible board is the interesting part.

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Circuit Boards You Can Stretch: Liquid Metal Nanomaterials Make A Strange Flex

November 19, 2020 by 9 Comments

If you think polyimide-based flexible PCBs are cool, wait until you get a load of what polymerized liquid metal networks can do.

Seems like [CNLohr] has some pretty cool friends, and he recently spent some time with a couple of them who are working with poly LMNs and finding out what they’re good for. Poly LMNs use a liquid metal composed of indium and gallium that can be sprayed onto a substrate through a laser-cut stencil. This results in traces that show the opposite of expected behavior; where most conductors increase in resistance when stretched, pol LMNs stay just as conductive no matter how much they’re stretched.

The video below shows [CNLohr]’s experiments with the stuff. He brought a couple of traditional PCB-based MCU circuits, which interface easily with the poly LMN traces on a thick tape substrate. Once activated by stretching, which forms the networks between the liquid metal globules, the traces act much like copper traces. Attaching SMD components is as simple as sticking them to the tape — no soldering required. The circuits remain impressively stretchy without any apparent effect on their electrical properties — a characteristic that should prove interesting for wearables circuits, biological sensors, and a host of real-world applications.

While poly LMNs aren’t exactly ready for the market yet, they don’t seem terribly difficult to make, requiring little in the way of exotic materials or specialized lab equipment. We’d love to see someone like [Ben Krasnow] pick this up and run with it — it seems right up his alley.

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Slipping Sheets Map Multiple Bends In This Ingenious Flex Sensor

June 26, 2020 by 23 Comments

When thoughts turn to measuring the degree to which something bends, it’s pretty likely that strain gauges or some kind of encoders on a linkage come to mind. Things could be much simpler in the world of flex measurement, though, if [Fereshteh Shahmiri] and [Paul H. Dietz]’s capacitive multi-bend flex sensor catches on.

This is one of those ideas that seems so obvious that you don’t know why it hasn’t been tried before. The basic idea is to leverage the geometry of layered materials that slip past each other when bent. Think of the way the pages of a hardbound book feather out when you open it, and you’ll get the idea. In the case of the ShArc (“Shift Arc”) sensor, the front and back covers of the book are flexible PCBs with a series of overlapping pads. Between these PCBs are a number of plain polyimide spacer strips. All the strips of the sensor are anchored at one end, and everything is held together with an elastic sleeve. As the ShArc is bent, the positions of the electrodes on the top and bottom layers shift relative to each other, changing the capacitance across them. From the capacitance measurements and the known position of each pad, a microcontroller can easily calculate the bend radius at each point and infer the curvature of the whole strip.

The video below shows how the ShArc works, as well as several applications for the technology. The obvious use as a flex sensor for the human hand is most impressive — it could vastly simplify [Will Cogley]’s biomimetic hand controller — but such sensors could be put to work in any system that bends. And as a bonus, it looks pretty simple to build one at home.

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Hinge Brings New Meaning To Flexible PCB

June 26, 2020 by 9 Comments

It is not a secret that flexible PC boards can bend. But despite the substrate’s flexibility, you can’t really fold them completely over. That bothered [Carl] so he developed a hinge design so that he can fold a board completely in half. You can watch a video showing an example, FlexBox, below.

Normal boards can fold over, but the copper traces can’t tolerate a very tight bend radius. [Carl’s] trick is to make the folding part have no traces at all. Only a small bridge carries traces between the two halves and it is allowed to bend almost like an interconnecting cable.

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Flexible PCB Earrings Put The Art In Art Deco

May 24, 2020 by 5 Comments

Earrings have been a hackers’ target for electronic attachment for quite a while, but combining the needed components into a package small enough to wear in that finicky location is quite a challenge. If [Sawaiz Syed]’s Art Deco Earrings are anything to go by, ear computers have a bright future ahead of them!

This is a project unusually well described by its name. It is in fact an earring, with art deco styling. But that sells it way too short. This sliver of a flex circuit board is double sided to host an ATtiny, accelerometer, LDO, and eight 2020 formfactor controller-integrated LEDs. Of course it’s motion sensitive, reacting to the wearer’s movement via LED pattern. [Sawaiz] makes reference to wearing it while dancing, and we can’t help but imagine an entire ballroom all aglow with tiny points of LED light.

The Art Deco Earrings are also set apart by the thoroughness of their documentation (have we mentioned how much we love detailed documentation?). [Sawaiz] not only drops the source in your lap, but the README in the Github repo linked at the top walks the reader through each component of the design in detail. Plus the PCBA render is so complete it includes a model of the wire loop to fit through the wearer’s ear; how cool is that? The single piece that’s still in progress is the battery. The earring itself hosts an LDO, so all that is required is stashing a battery somewhere discrete, perhaps in the user’s hair? We’re looking forward to seeing what [Sawaiz] works out.

For the full effect, check out the gif of an assembled unit in action after the break.

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