While our attention is mostly directed towards ever smaller-integrated silicon circuits providing faster and faster computing, there’s another area of integrated electronics that operates at a much lower speed which we should be following. Thin-film flexible circuitry will provide novel ways to place electronics where a bulky or expensive circuit board with traditional components might be too expensive or inappropriate, and Wikichip is here to remind us of a Leuven university team who’ve created what is claimed to be the fastest thin-film flexible microprocessor yet. Some of you might find it familiar, it’s our old friend the 6502.
The choice of an archaic 8-bit processor might seem a strange one, but we can see the publicity advantage — after all, you’re reading about it here because of it being a 6502. Plus there’s the advantage of it being a relatively simple and well-understood architecture. It’s no match for the MHz clock speeds of the original with an upper limit of 71.4 kHz, but performance is not the most significant feature of flexible electronics. The production technology isn’t quite ready for the mainstream so we’re unlikely to be featuring flexible Commodore 64s any time soon, but the achievement is the impressive feat of a working thin-film flexible microprocessor.
If the Cortex family of embedded microprocessors aren’t flexible enough for your designs, an article published this week (click here for the PDF version) in the journal Nature might be of interest. We’re not talking flexibility in terms of features, but real, physical flexibility of the microprocessor itself. A research team from Arm Ltd. has developed the PlasticArm, which is a 32-bit processor derived from the Cortex-M0+ family.
They accomplished this by constructing a CPU from metal-oxide thin-film transistors (TFT) on a polyimide substrate, the resultant chip being called a natively flexible microprocessor. While much of the hype focuses on the flexibility aspect, we think the real innovation here is the low cost. The processes used to deposit transistors onto silicon wafers is much more expensive than those on this flexible substrate.
Don’t get too excited just yet, because there were some compromises made along the way. Modern microprocessor silicon dies are measured in the tens of microns, but the PlasticArm total die size is a comparatively whopping 9 mm square. The researchers were appropriately focused on the core CPU, and the auxiliary building blocks such as ROM and RAM seem almost an afterthought. With only 456 bytes of program store and 128 bytes of RAM, only the tiniest of applications are suited to this chip. Other compromises were made, such as no internal registers — they are mapped to the external RAM — and the CPU runs a lot slower than we’re used to, topping out at 29 kHz (note: k not M).
There are certainly some challenges with this new technology, and we won’t be designing with these chips any time soon. But it has the potential to offer benefits in certain niche applications where low-cost and/or flexibility is more important than processor speed and performance.
In the beginning, there was hot glue. Plus some tape, and a not inconsiderable amount of Bondo. In general, building custom portable game consoles a decade or so in the past was just a bit…messier than it is today. But with all the incredible tools and techniques the individual hardware hacker now has at their disposal, modern examples are pushing the boundaries of DIY.
This Zelda: Ocarina of Time themed portable N64 by [Chris Downing] is a perfect example. While the device is using a legitimate N64 motherboard, nearly every other component has been designed and manufactured specifically for this application. The case has been FDM 3D printed on a Prusa i3, the highly-detailed buttons were printed in resin on a Form 3, and several support PCBs and interface components made the leap from digital designs to physical objects thanks to the services of OSH Park.
Today, those details are becoming increasingly commonplace in the projects we see. But that’s sort of the point. In the video after the break, [Chris] breaks down the evolution of his portable consoles from hacked and glued together monstrosities (we mean that in the nicest way possible) to the sleek and professional examples like his latest N64 commission. But this isn’t a story of one maker’s personal journey through the ranks, it’s about the sort of techniques that have become available to the individual over the last decade.
Case in point, custom flexible flat cables (FFC). As [Chris] explains, when you wanted to relocate the cartridge slot on a portable console in the past, it usually involved tedious point-to-point wiring. Now, with the low-volume production capabilities offered by companies like OSH Park, you can have your own flexible cables made that are neater, faster to install, and far more reliable.
We all have a gaming system in our pocket or purse and some of us are probably reading on it right now. That pocket space is valuable so we have to budget what we keep in there and adding another gaming system is not in the cards, if it takes up too much space. [Kevin Bates] budgeted the smallest bit of pocket real estate for his full-size Arduboy clone, Arduflexboy. It is thin and conforms to his pocket because the custom PCB uses a flexible substrate and he has done away with the traditional tactile buttons.
Won’t a flexible system be hard to play? Yes. [Kevin] said it himself, and while we don’t disagree, a functional Arduboy on a flexible circuit makes up for practicality by being a neat manufacturing demonstration. This falls under the because-I-can category but the thought that went into it is also evident. All the components mount opposite the screen so it looks clean from the front and the components will not be subject to as much flexing and the inputs are in the same place as a traditional Arduboy.
cost = low, practicality = extremely low, customer service problems = high
These flexible circuit boards use a polyimide substrate, the same stuff as Kapton tape, and ordering boards is getting cheaper so we can expect to see more of them popping up. Did we mention that we currently have a contest for flexible circuits? We have prizes that will make you sing, just for publishing your flex PCB concept.
Two researchers of Responsive Environments, MIT Media Lab, have put to together a device that is an amazing array of musical instruments squeezed into one flexible package. Made using seven layers of fabrics with different electrical properties, the result can be played using touch, proximity, pressure, stretch, or with combinations of them. Using a fabric-based keyboard, ribbon-controller, and trackpad, it can be played as a one-octave keyboard, a theremin, and in ways that have no words, such as stretching while pressing keys. It can also be folded up and stuffed into a case along with your laptop, and care has even been taken to make it washable.
Layer one, the top layer, is a conductive fabric for detecting proximity and touch. The twelve keys can work independently with a MPR121 proximity touch controller or the controller can treat them all as one, extending the distance the hand can be and have it still work. Layer two is just a knit fabric but layers three to six detect pressure, consisting to two conductive layers with a mesh fabric and a piezo-resistive fabric in between. The piezo-resistive fabric is LTT-SPLA from eeonyx, a knit fabric coated with the conductive polymer, polypyrrole (PPy). Layer seven consists of two strips of knitted spandex fabric, also coated with PPy, and detects stretching. Two strips of this are sewn on the bottom, one horizontal and one vertical. You can see and hear the amazing sound this all produces in the video below.
You can find flex PCBs in just about every single piece of consumer electronics. These traces of copper laminated in sheets of Kapton are everywhere, and designing these cables, let alone manufacturing them, is a dark art for the garage electronics wizard. Having these flat flex cables and PCBs manufactured still requires some Google-fu or a contact at a fab house, but at least now designing these cables is a solved problem.
[Oli] needed a way to connect two PCBs together over a moving part. Usually this means some sort of connector or cable, but he’s developed an even better solution – flexible PCB connections. To generate these copper traces sandwiched between a few layers of Kapton, [Oli] wrote a Python script to take a set of parameters, and produces an design for Eagle that includes all the relevant bits.
Of course, with a flexible PCB layout, the question of how to get these manufactured comes up. we’ve seen a few creative people make flexible PCBs with a 3D printer and there’s been more than one Hackaday Prize project using these flex PCBs. [Oli] says any manufacturer of flexible circuits should be able to reproduce everything generated from his script without much thinking at all. All we need now is for OSH Park to invent purple Kapton.
As circuits find their way into more and more real-world environments, the old standard circuitry isn’t always up to the task. It wasn’t that long ago that a computer needed special power, cooling, and a large room. Now those computers wouldn’t cut it for the top-of-the-line smartphone. However, most modern circuits don’t bend well and don’t like getting wet.
An international team of researchers is developing chemical-based circuitry that uses gold nanoparticles and electrically charged organic molecules to build circuit elements that behave like semiconductor diode junctions. It’s simple to make flexible circuits that don’t mind being wet using this chemical soup.
In an interview with IEEE Spectrum, the developers mentioned that other circuit elements similar to transistors and light sensors should be possible. The circuits aren’t perfect, however. The switching speed needs improvement. Also, while conventional circuits don’t like to get wet, these chemical circuits have difficulties if things get dry. Still, like all technology, things will probably improve over time.
This technology needs a good bit of engineering refinement before it is practical. If you need flexible photosensitive circuits in the near term, you might try here. Meanwhile, waterproof circuitry just needs the right kind of enclosure.