The ever-shrinking size of electronics and sensors has allowed wearables to help us quantify more and more about ourselves in smaller and smaller packages, but one major constraint is the size of the battery you can fit inside. What if you could remotely power a wearable device instead?

Researchers at Carnegie Mellon University were able to develop a power transmitter that lets power flow over human skin to remote devices over distances as far a head-to-toe. The human body can efficiently transmit 40 MHz RF energy along the skin and keeps this energy confined around the body and through clothing, as the effect is capacitive.

The researchers were able to develop several proof-of-concept devices including “a Bluetooth
ring with a joystick, a stick-and-forget medical patch which logs data, and a sun-exposure patch with a screen — demonstrating user input, displays, sensing, and wireless communication.” As the researchers state in the paper, this could open up some really interesting new wearable applications that weren’t possible previously because of power constraints.

If you’re ready to dive into the world of wearables, how about this hackable smart ring or a wearable that rides rails?

[Sophia Dai] brings us a project you will definitely like if you’re tired of traditional peripherals like a typical keyboard and mouse combo. This is ErgO, a smart ring you can build out of a few commonly available breakouts, and it keeps a large number of features within a finger’s reach. The project has got an IMU, a Pimoroni trackball, and a good few buttons to perform actions or switch modes, and it’s powered by a tiny Bluetooth-enabled devboard so it can seamlessly perform HID device duty.

While the hardware itself appears to be in a relatively early state, there’s no shortage of features, and the whole experience looks quite polished. Want to lay back in your chair yet keep scrolling the web, clicking through links as you go? This ring lets you do that, no need to hold your mouse anymore, and you can even use it while exercising. Want to do some quick text editing on the fly? That’s also available; the ErgO is designed to be used for day to day tasks, and the UX is thought out well. Want to use it with more than just your computer? There is a device switching feature. The build instructions are quite respectable, too – you can absolutely build one like this yourself, just get a few breakouts, a small battery, some 3D printed parts, and find an evening to solder them all together. All code is on GitHub, just like you would expect from a hack well done.

Looking for a different sort of ring? We’ve recently featured a hackable cheap smart ring usable for fitness tracking – this one is a product that’s still being reverse-engineered, but it’s alright if you’re okay with only having an accelerometer and a few optical sensors.

We’ve seen prolific firmware hacker [Aaron Christophel] tackle smart devices of all sorts, and he never fails to deliver. This time, he’s exploring a device that seems like it could have come from the pages of a Cyberpunk RPG manual — a shiny chrome Bluetooth Low Energy (BLE) smart ring that’s packed with sensors, is reasonably hacker friendly, and is currently selling for as little as $20.

The ring’s structure is simple — the outside is polished anodized metal, with the electronics and battery carefully laid out along the inside surface, complete with a magnetic charging port. It has a BLE-enabled MCU, a heartrate sensor, and an accelerometer. It’s not much, but you can do a lot with it, from the usual exercise and sleep tracking, to a tap-sensitive interface for anything you want to control from the palm of your hand. In the video’s comments, someone noted how a custom firmware for the ring could be used to detect seizures; a perfect example of how hacking such gadgets can bring someone a brighter future.

The ring manufacturer’s website provides firmware update images, and it turns out, you can upload your own firmware onto it over-the-air through BLE. There’s no signing, no encryption — this is a dream device for your purposes. Even better, the MCU is somewhat well-known. There’s an SDK, for a start, and a datasheet which describes all you would want to know, save for perhaps the tastiest features. It’s got 200 K of RAM, 512 K of flash, BLE library already in ROM, this ring gives you a lot to wield for how little space it all takes up. You can even get access to the chip’s Serial Wire Debug (SWD) pads, though you’ve got to scrape away some epoxy first.

As we’ve seen in the past, once [Aaron] starts hacking on these sort of devices, their popularity tends to skyrocket. We’d recommend ordering a couple now before sellers get wise and start raising prices. While we’ve seen hackers build their own smart rings before, it’s tricky business, and the end results usually have very limited capability. The potential for creating our own firmware for such an affordable and capable device is very exciting — watch this space!

We thank [linalinn] for sharing this with us!

We like to keep a pulse on the latest biosensor research going on around the world. One class of biosensors that have really caught our attention is the so-called thin-film sensors, pioneered by the Rogers Research Group at Northwestern University.

We’re no strangers to the flexible PCB here at Hackaday. Flexible PCBs have become increasingly accessible to small-scale developers and hobbyists, explaining why we’re seeing them incorporated into many academic research projects. The benefit of these types of sensors lies in the similarity of their mechanical properties to those of human skin. Human skin is flexible, so matching the flexibility of skin allows these thin-film sensors to adhere more comfortably and naturally to a person’s body.

The circuits used in these thin-film sensors are what we’ve grown accustomed to. An instrumentation amplifier to measure heart rate (and oftentimes respiratory rate) from the electrocardiogram, a light-emitting diode, and photosensor pair to measure heart rate, respiration, and blood oxygen from the photoplethysmograph, a thermistor or non-contact infrared sensor to measure temperature, and an accelerometer to measure activity. Really the beauty behind what the Rogers group has done lies in their flexible PCB design. They’re strategically using serpentine interconnects between modular components of the PCB, allowing the circuit to bend and fold in predetermined locations. All that’s left is some good low-modulus silicone to cover the electronics and give the device a nice, soft-to-touch surface, adding to the comfort level of the user.

Really, this strategy is no different than what we’ve explored here at Hackaday, and we’re happy to see others finding utility in flexible PCBs as well, especially for medical applications. We like to think that maybe the Rogers group has been inspired by the many creative projects that have graced the front page of Hackaday and hope that you are inspired to keep on hacking as well.

If you’re feeling underwhelmed by yet another smartwatch announcement, then researchers at the University of Maryland may have just the wearable for you. Instead of just tracking your movement from one spot, Calico winds around you like a cartoon sidekick.

Using a “railway system,”(PDF) the Calico can travel around a garment to get better telemetry than if it were shackled to a wrist. By moving around the body, the robot can track exercise, teach dance moves, or take up-close heart measurements. Tracks can be magnetically linked across garments, and Calico can use different movement patterns to communicate information to the user.

This two-wheeled robot that rides the rails is built around a custom PCB with a MDBT42Q microcontroller for a brain which lets it communicate with a smartphone over Bluetooth Low Energy. Location is monitored by small magnets embedded in the silicone and plastic living hinge track, and it can use location as a way to provide “ambient visual feedback.”

The researchers even designed a friendly cover for the robot with googly eyes so that the device feels more personable. We think animated wearables could really take off since everyone loves cute animal companions, assuming they don’t fall into the uncanny valley.

If you love unusual wearables as much as we do, be sure to check out Wearable Sensors on Your Skin and the Wearable Cone of Silence.

As microcontroller prices drop, they appear in more things. Today you will find microcontrollers in your car, your household appliances, and even kid’s toys. But you don’t see them often embedded in things that are either super cheap or have to flex, such as for example a bandage. Part of the reason is the cost of silicon chips and part of the reason is that silicon chips don’t appreciate bending. What if you could make CPUs for less than a penny out of flexible plastic? What applications would that open up? PragmatIC — a company working to make this possible — thinks it would open up a whole new world of smart items that would be unthinkable today. They worked with a team at the University of Illinois Urbana-Champaign to create prototype plastic CPUs with interesting results.

This is still the stuff of research and dreams, but a team of researchers did work to produce 4-bit and 8-bit processors using IGZO –indium gallium zinc oxide — semiconductor technology. This tech can be put on plastic and will work even if you bend it around a radius as small as a few millimeters.

The key problem, it seems, is yield. When ARM put the 32-bit M0 CPU on plastic, the yield was poor because of the high gate count. These new processors are simplified 4-bit devices that account for the 81% yield. At that yield, the devices could cost less than a penny to produce.

The final design fits on a 5.6 square millimeter die and had about 2,100 devices — comparable to an Intel 4004. The M0, by contrast, contains over 56,000 devices. The 8-bit plastic CPUs also worked but had a correspondingly lower yield. What would you do with a flexible CPU that costs a penny or two? Is it going to require more than a simple 4-bit processor?

Of course, the University of Illinois Urbana-Champaign is the home of a very famous fictional computer and some not-so-fictional ones. By the way, although the M0 was put on plastic, it wasn’t without significant compromises.

TshWatch is a project by [Ivan / @pikot] that he’s been working on for the past two years. [Ivan] explains that he aims to create a tool meant to help you understand your body’s state. Noticing when you’re stressed, when you haven’t moved for too long, when your body’s temperature is elevated compared to average values – and later, processing patterns in yourself that you might not be consciously aware of. These are far-reaching goals that commercial products only strive towards.

At a glance it might look like a fitness tracker-like watch, but it’s a sensor-packed logging and measurement wearable – with a beautiful E-Ink screen and a nice orange wristband, equipped with the specific features he needs, capturing the data he’d like to have captured and sending it to a server he owns, and teaching him a whole new world of hardware – the lessons that he shares with us. He takes us through the design process over these two years – now on the fifth revision, with first three revisions breadboarded, the fourth getting its own PCBs and E-Ink along with a, and the fifth now in the works, having received some CAD assistance for battery placement planning. At our request, he has shared some pictures of the recent PCBs, too!

And sensor-packed, it is! There’s a MAX30100 for heart rate measurement, DS3231 RTC for timekeeping and interrupts, MLX90615 IR temperature sensor for contact-less skin temperature measurements, an LSM6DS3C IMU with, so to say, hardware-accelerated pedometer capabilities, and a BME680 air quality, humidity, pressure and temperature sensor. To keep the watch low-power despite the ESP32’s appetite, [Ivan] has conquered the ESP32’s ULP – a low-power co-processor capable of talking to all the project’s I2C devices. Having never written ULP Assembly before, he eventually wrote ULP drivers for all of the devices involved. As a result, it can already survive for over 36 hours at a single charge, and he is aiming to make it last a week.

[Ivan] invites you to join his effort – it takes time to build a device for a far-reaching and almost sci-fi realm goal like this, and he could use help in under-explored areas. He’s been mostly working with hardware and firmware so far, and if you’d like to help with software, datalogging, design/CAD, or improve any other areas, do join the Hackaday.io chatroom and see how far we can get from here! Hardware feature progress is being tracked on GitHub, and there’s also a video in Russian explaining the hardware architecture of the fourth revision and the challenges, caringly subtitled in English for us, embedded below.

What are we hackers looking for in a wrist-worn device aimed to help us day-to-day? We’ve discussed that with you all before.