Stretchable Traces for Flexible Circuits

Electronic components are getting smaller and smaller, but the printed circuit boards we usually mount them on haven’t changed much. Stiff glass-epoxy boards can be a limiting factor in designing for environments where flexibility is a requirement, but a new elastic substrate with stretchable conductive traces might be a game changer for wearable and even implantable circuits.

qxMo1DResearchers at the Center for Neuroprosthetics at the École Polytechnique Fédérale de Lausanne are in the business of engineering the interface between electronics and the human nervous system, and so have to overcome the mismatch between the hardware and wetware. To that end, [Prof. Dr. Stéphanie P. Lacour]’s lab has developed a way to apply a liquid metal to polymer substrates, with the resulting traces capable of stretching up to four times in length without cracking or breaking. They describe the metal as a partially liquid and partially solid alloy of gallium, with a gold added to prevent the alloy from beading up on the substrate. The applications are endless – wearable circuits, sensors, implantable electrostimulation, even microactuators.

Looks like progress with flexibles is starting to pick up, what with the conductive silicone and flexible phototransistors we’ve covered recently. We’re excited to see where work like this leads.

Continue reading “Stretchable Traces for Flexible Circuits”

Flexible Phototransistor Will Make Everything Subtly Better In The Future

University of Wisconsin-Madison is doing some really cool stuff with phototransistors. This is one of those developments that will subtly improve all our devices. Phototransistors are ubiquitous in our lives. It’s near impossible to walk anywhere without one collecting some of your photons.

The first obvious advantage of a flexible grid of phototransistors is the ability to fit the sensor array to any desired shape. For example, in a digital camera the optics are designed to focus a “round” picture on a flat sensor. If we had a curved surface, we could capture more light without having to choose between discarding light, compensating with software, or suffering the various optical distortions.

Another advantage of the University’s new manufacturing approach is the “flip-transfer” construction method they came up with. They propound that their method produces a vastly more sensitive device. The sensing silicon sits on the front of the assembly without any obstructing material in front; also the metal substrate it was built on before flipping is reflective; also increasing the sensitivity.

All in all very cool, and we can’t wait for phone cameras, with super flat lenses, infinite focus, have no low light capture issues, and all the other cool stuff coming out of the labs these days.

State-Aware Foldable Electronics Enters The Third Dimension

Still working with PCBs in 2D? Not [Yoav]. With some clever twists on the way we fab PCBs, he’s managed to create a state-aware foldable circuit board that responds to different configurations.

From his paper [PDF warning], [Yoav] discusses two techniques for developing foldable circuits that may be used repeatedly. The first method involves printing the circuit onto a flexible circuit board material and then bound front-and-back between two sheets of acrylic. Valid folded edges are distinguished by the edges of individual acrylic pieces. The second method involves laying out circuits manually via conductive copper tape and then exposing pads to determine an open or closed state.

Reconfigurable foldable objects may open the door for many creative avenues; in the video (after the break), [Yoav] demonstrates the project’s state-awareness with a simple onscreen rendering that echoes its physical counterpart.

While these circuits are fabbed from a custom solution, not FR1 or FR4, don’t let that note hold your imagination back. In fact, If you’re interested with using PCB FR4 as a structural element, check out [Voja’s] comprehensive guide on the subject.

Continue reading “State-Aware Foldable Electronics Enters The Third Dimension”

Electric Longboard has a Flexy Battery Pack Design

DIY electric longboards are a ton of fun to build and ride (we’ve featured several builds before). Most boards have batteries strapped to the bottom of a rigid board, or they have battery packs near each truck so the board can still flex. Instead of going with either of these designs, [Ben] created a custom battery pack design that’s able to flex with the board.

[Ben]’s pack is made up of A123 26650 cells nestled in his custom-fabricated enclosure. [Ben] designed his pack in CAD and used a CNC machine to create a foam mold. He used the mold to do a fiberglass layup, vacuum-bagged it, and left it to cure. Since the fiberglass bonded really well to the foam, [Ben] used acetone to dissolve the foam while leaving his fiberglass layup intact.

Bendy battery pack on longboard[Ben]’s pack fits 18 cells which he soldered together with some flexible copper grounding wire. The top side of the enclosure is covered with a layer of insulating rubber, and the rim is covered with a soft foam to form a gasket against the board. As you can see, the pack bends really well with the board, and  it doesn’t look like [Ben] has had any issues with his design so far. Check out [Ben]’s blog for more info and for more details on the overall design of his board.

Hackaday Links: March 3, 2014


If you’re playing along with Twitch Plays Pokemon, you might as well do it the right way: with the smallest Game Boy ever, the Game Boy Micro. [Anton] needed a battery replacement for this awesome, discontinued, and still inexplicably expensive console and found one in a rechargeable 9V Lithium battery. You get two replacement cells out of each 9V battery, and a bit more capacity as well.

Every garden needs garden lights, right? What does every garden light need? A robot, of course. These quadruped “Toro-bots” react to passersby by brightening the light or moving out of the way. It’s supposed to be for a garden that takes care of itself, but we’re struggling to figure out how lights will do that.

Flexiable 3D prints are all the rage and now resin 3D printers are joining the fray. The folks at Maker Juice have introduced SubFlex, a flexible UV-curing resin. The usual resins, while very strong, are rock solid. The new SubFlex flexible resins are very bendable in thin sections and in thicker pieces something like hard rubber. We’re thinking custom tank treads.

Remember this post where car thieves were using a mysterious black box to unlock cars? Looks like those black boxes have moved from LA to Chicago, and there’s still no idea how they work.

Have a Google Glass? Can you get us on the list? [Noé] and [Pedro] made a 3D printed Google Glass adapter for those of us with four eyes.

Laser cutting technique makes plywood bendable

Here’s a laser cutting technique that makes thin plywood bendable. By cutting away elongated diamond shapes from the material, a lattice of strips connected minimally by alternating tabs is left over. The wood is then bendable, and it must be somewhat durable since the idea came from a product that uses the technique as a hinged notebook enclosure.

We don’t have much interest in it as an often used pivot point as surely it must be a problem with long-term use. But we love the look of it as a rounded corner on an enclosure like the Arduino project box seen above. The side walls are one continuous piece, with identical top and bottom sections which receive the alignment tabs. The whole thing is held together with just four bolt/washer/nut combinations.

But if you don’t have access to a laser cutter, we guess you’ll have to stick to altering pre-made enclosures for now.