Biosensors you stick to your skin

CBS ran an interesting article about tiny biosensor patches that monitor your health while they are stuck to your arm or leg. The article referenced work done by engineers at the University of Illinois at Urbana-Champaign and Northwestern University. You stick the biosensor to your skin like a temporary tattoo. The work was presented in a paper hidden behind a paywall at Sciencemag.org. The abstract reads:

“When mounted on the skin, modern sensors, circuits, radios, and power supply systems have the potential to provide clinical-quality health monitoring capabilities for continuous use, beyond the confines of traditional hospital or laboratory facilities. The most well-developed component technologies are, however, broadly available only in hard, planar formats. As a result, existing options in system design are unable to effectively accommodate integration with the soft, textured, curvilinear, and time-dynamic surfaces of the skin. Here, we describe experimental and theoretical approaches for using ideas in soft microfluidics, structured adhesive surfaces, and controlled mechanical buckling to achieve ultralow modulus, highly stretchable systems that incorporate assemblies of high-modulus, rigid, state-of-the-art functional elements. The outcome is a thin, conformable device technology that can softly laminate onto the surface of the skin to enable advanced, multifunctional operation for physiological monitoring in a wireless mode.”

This biosensor can monitor your health when adhered to your body.

What was telling about the paper were all the people involved:

Sheng Xu, Yihui Zhang, Lin Jia, Kyle E. Mathewson, Kyung-In Jang, Jeonghyun Kim, Haoran Fu, Xian Huang, Pranav Chava, Renhan Wang, Sanat Bhole, Lizhe Wang, Yoon Joo Na, Yue Guan, Matthew Flavin, Zheshen Han, Yonggang Huang, and MacArthur fellow John A. Rogers.

I am not sure if that is a list of grad student slaves or distinguished professors, but the CBS article neglected to mention that some of the authors represent Tsinghua University in Beijing, Zhejiang University in Hangzhou, and Hanyang University in Seoul. This long list confirms the observation of my pal Ed Fong that system-level design requires engineers that are more social than IC designers and, I suspect, programmers. Ed has done both IC design and worked in complex electro-mechanical systems, so he should know. When you do a complex system like these biosensors it only stands to reason you would need a lot of people involved since there is so much expertise needed in so many areas.

The flexible sensor is like a temporary tattoo, it can bend and flex with your body in order to stay attached and keep working.

Here is a closeup.

And an ultra-close-up.

The new paper implements a complete system based on these biosensors. Adding a power system and a microcontroller and probably a radio is not trivial, hence the large crown of contributors. Another thing that makes me proud of the recent paper is that it has contributors from the US, China, and Korea. That is what I love about technology and engineering. While other industries and politicians give lip service to diversity, the tech industry has practiced it for decades. Here in Silicon Valley every tech company is more like the United Nations. As long as you know what you are doing, you can work anywhere you want, and that is something we all should be proud of.

Here is a biosensor as it would appear adhered to a heart.

Speaking of medical devices, my pal Ken Carroll went to work for Nanostim over 5 years ago. The idea is to make a heart pacemaker so small that you can just attach it to the heart. The wires of a pacemaker are one of the most problematic components, and they wear out and need replacement before the pacemaker battery dies.

This Nanostim pacemaker is 1/10 the size of a conventional one. It is implanted directly in the heart, needing no fragile wires to deliver the pulses to the heart.

Here is the Nanostim pacemaker in-situ.

Ken is a great IC designer, and if anyone can make a chip small enough and low-power enough, he can. I see Nanostim was acquired by St Jude’s Medical last year, so that is good news for all the people that worked for so many years to make this a reality. I have a mechanical engineer buddy that works at a laser eye surgery place, and he tells me it is really exacting work when you have to keep the FDA happy.

Atmel’s Rob Valiton talks automotive

Rob Valiton, Senior VP and General Manager at Atmel, was recently interviewed by Alix Paultre of Power Systems Design.

During the podcast – which can be heard here – the two spoke about various issues surrounding automotive systems and the multiple, often conflicting challenges involved in designing for the application space.

The interview was conducted in the midst of CES 2014, shortly after Atmel officially unveiled its AvantCar curved touch screen console concept. 

The fully functional console features two large curved touchscreen displays – without mechanical buttons. Instead, the touchscreens integrate capacitive touch buttons and sliders, allowing users to navigate general applications typically found within an automotive center console.

As we’ve previously discussed on Bits & Pieces, Atmel’s extensive automotive portfolio encompasses a wide range of products including body electronics, networking and access systems, as well as engine, lighting and entertainment components.

 More specifically, our components are designed to fit small footprints, consume very little power and operate in high temperature and electromagnetic environments. To be sure, Atmel’s highly integrated designs can help save manufacturers significant component costs and months of development, integration and prototype time.

“Atmel’s broad product portfolio ranges from low-cost, entry level devices to advanced, highly integrated ICs with a broad range of functionalities, extensive connectivity, refined interfaces and strong security,” and Atmel engineering rep told Bits & Pieces. “Our products are designed in state-of-the-art BCDMOS, BDC-on-SOI, or non-volatile CMOS technologies and meet strict automotive qualification standards.”

Interested in learning more about Atmel’s automotive portfolio? You can check out our automotive-qualified category breakdown below:

• Microcontrollers (MCUs)
• 
Serial EEPROMs

• Touch (maXTouch)
• Broadcast radio
• 
CAN/VAN networking
• Car access
• Drivers/high temperature ICs
• 
Battery management
• LIN networking

A Tesla hacked into a Vanagon

My buddy Otmar Ebenhoech is hacking a wrecked Tesla chassis underneath a VW Vanagon van. And not just any Vanagon, he is doing it to a stretched Vanagon that has two side doors.

Otmar Ebenhoech stretched this Vanagon years ago. When the engine blew out he decided to hack a wrecked Tesla S into the undercarriage.

I met Otmar when he lived in Silicon Valley. I was converting a 1975 Honda Civic to all-electric, and he was the go-to guy for help and advice. He sold his house during the housing craze, and went up and bought a house and a shop up in Corvalis Oregon. If anyone has the can-do spirit to pull this off, it is Otmar. He is the designer of the Zilla dc motor controller used in the White Zombie electric drag car.

Here is a video from the project blog:

Hopefully Burning Man and all Otmar’s other projects won’t keep him from this great adventure. I saw he paid about $38k for the Tesla so its not something you want to just let sit. When I watched the video  above I wrote Otmar and asked if that hoist was his personal shop. He replied:

“Yes, that’s the Garage Mahal you see in the background. I spoiled myself by moving to Oregon where I can afford a shop, and seemingly to buy a wrecked model S though I’m still in a bit of shock over that!”

Arc explosions illustrate the dangers of electricity

I wrote a blog post a while back about the difficulty or having cars with 42V instead of 12V batteries. I also pointed out the difficulties of distributing dc inside your house and to your house. It got picked up by EDN, and the comments were interesting. Someone challenged my assertion that 24V relays switches are less reliable. Sorry, I worked for GMC Truck and Coach as an auto engineer in the electrical group. Heck, just read any switch or relay datasheet and you can see you have to de-rate for dc and de-rate even more for higher-voltage dc. Someone pointed out the phone company uses 48V dc, and I had to explain that the 48V the POTS (plain-old telephone system) sends to your house is also high impedance, 600 ohms, so that make is much less arc-prone and easier to switch.

Others challenged my observation that it is hard to distribute dc in your house due to the fire hazard from the arcs and the same problems with switches and relays. Well, even ac has arcs that are hard to quench. Bigger dc circuit breakers have magnets in them to pull the arc one side and make it longer so it can break. Really big breakers, both ac and dc, have compressed air that blows the arc out just like your kid with a birthday candle.

So here is a nice video of an ac arc flash that should give you some idea of the difficulty of quenching an arc. Palo Verde had a horrible arc flash in 2008 that thankfully had no injuries. And here is a training video of an arc flash form the fine folks at e-Hazard.com

Here is another training video from Westex flameproof clothing:

And if you wondered if there was any glory left in the American worker, check out this high-voltage lineman working from a helicopter.

So that’s the trouble with dc. Since the voltage is not going through zero 120 times a second it is much harder to quench the arc. The operative word is “plasma”. That is what Fran Hoffart from Linear Tech taught me about li-ion batteries. He said that the burning lithium is certainly a problem. But the real mess is that a plasma ball forms, and that shorts out any other battery cells in the vicinity. An arc is plasma, and that is some nasty stuff. I mentioned to Fran that the iron phosphate chemistry lithium cells are supposed to be burn-proof. Fran looked at me with an expression that said “you can’t be that stupid” and replied “they all burn”. It is remarkable the difference you hear when talking to people who are making and selling the battery cells versus the people like Fran, that are making the chips to reliably charge the cells.

I guess that is why that outlaw biker told me that the only thing that he was really scared of was electricity. I asked why and he said “Because it can kill you and you can’t see it.”

Cure RF squegging with a Neutrodyne circuit

Some headlines write themselves, huh? Squegging is when an RF amplifier or MHz-class switching regulator starts cycling on and off. In an audio amp it is called “motorboating” since that is the sound it makes. FET amplifiers are subject to this, like old tube amplifiers. Both have a high-impedance input, the tube grid or the FET gate. A FET gate is capacitive, so any charge that gets put on it will be stored by the gate, moving the bias point of the FET too high, and causing squegging. The Neutrodyne circuit comes from 1920 vacuum tube amplifiers. It is one of the ways you can tame squegging. High Frequency Electronics magazine has a nice article about squegging (pdf). The best way to show it is a figure in the article, who I hope the fine legal team at Summit Technical Media will let me show you.

Squegging is when the input of a FET or vacuum tube floats up momentarily and shuts down oscillations. This make the output cycle on and off, called motorboating (courtesy High Frequency Electronics).

Trust me; you really want to click over to the article since it has the schematics of a FET amplifier that will start to motor boat, as well as several ways to fix it. The whole magazine is pretty good. While you are at it, think of signing up for a print copy of the magazine. You need to be an engineer or tech worker, since the magazine is audited by BPA, so the advertisers know they are reaching tech people and not random idiots.

Remember that these tips apply to high frequency switching converters. And regulators are getting up into RF ranges. I remember seeing an 8-MHz switching regulator from Micrel years ago when I worked at EDN magazine. You might be using one of these fast regulators for some extreme size problems. These high speeds do cause less efficiency, as the gate charge is getting shunted to ground, but the inductor you need with these fast converters is miniscule. That Micrel part still manages 90% max efficiency, but you can use a 0.47µH inductor. That is one tiny inductor.

So I assume the Micrel folks have solved any squegging problems in their part, but it is still a good principle to understand should you run across it. It’s like sub-harmonic oscillations in switchers with a duty cycle greater than 50% (pdf page 10, pdf page 5, pdf page 72. It might befuddle you if you have never heard of it and don’t know the steps you need to take to solve it.

Solar-powered batteries woven into fabric for wearables

A new generation of solar-powered wearable electronics could soon be hitting the streets, with batteries inconspicuously woven into clothing fibers or incorporated into watchbands.

Image Credit: Adafruit

As a recent article published in Nano Letters notes, electronic textiles have the potential to integrate smartphone functions into clothes, eyeglasses, watches and materials worn on the skin. Possibilities range from the practical – for example, allowing athletes to monitor vital signs – to the aesthetic, such as lighting up patterns on clothing.

However, the article identified current battery technology as the primary “bottleneck,” responsible for slowing progress toward the development of a wider range of flexible e-fabrics and materials. Indeed, a number of wearable electronic items, such as smartwatches and Google Glass, still require a charger with a cord.

To unlink smart technology from the wall socket, a research team headed by Taek-Soo Kim, Jung-Yong Lee and Jang Wook Choi had to rethink what materials are best suited for use in a flexible, rechargeable battery that’s also inexpensive.

Image Credit: Adafruit

Ultimately, the team decided to test unconventional materials, discovering that they could coat polyester yarn with nickel and carbon – using polyurethane as a binder and separator to produce a flexible battery that kept working even after being folded and unfolded many times. The researchers also managed to integrate lightweight solar cells to recharge the battery without disassembling it from clothing or requiring the wearer to plug in.

As we’ve previously reported on Bits & Pieces, analysts at ABI Research have determined that wearable wireless device revenues will grow to exceed $6 billion in 2018. Of the four segments tracked, sports, fitness and wellness are the largest, never dropping below 50% share of all device shipments over the forecast period.

Amulet Pendant: Powered by Atmel’s ARM-based SAM4L MCU.

“Fitness activity trackers are quickly gaining popularity in the market,” confirmed ABI Research senior analyst Adarsh Krishnan. “Different from other more single-use or event-centric devices, activity trackers monitor multiple characteristics of the human body including movement, calories burned, body temperature and sleep tracking.”

Optimizing charge cycles and battery life

Bits & Pieces has been on a roll this week with an automotive theme in honor of the latest additions to Atmel’s touch family: the mXT336S and mXT224S. In this article, we’re going to take a closer look at how Atmel optimizes automotive charge cycles and battery life with its MCUs.

As automotive enthusiasts know, Li-ion technology is currently the first choice for modern high-performance batteries. To be sure, Li-ion batteries are up to 30 percent smaller and 50 percent lighter than conventional NiMH batteries – yet manage to store significantly more energy.

However, while the batteries do offer concrete advantages in terms of size, weight, recharge speed and resistance to memory effects, Li-ion has a higher cost compared to other battery types. Of course, this can definitely be improved by using a battery management system like Atmel’s which optimizes battery performance.

“Our Li-ion battery management solution offers high accuracy analog measurement functions in combination with efficient active cell balancing ensuring optimum usage of battery capacity,” an Atmel engineering rep told Bits & Pieces. “Specifically, the megaAVR, ATmega32HVE2 and ATmega64HVE2 microcontrollers (MCUs) can be used to improve the performance and longevity of 12V standard lead-acid batteries.”

As the engineering rep notes, the above-mentioned MCUs are designed for intelligent battery sensor applications – with the devices determining the state of charge and state of health for 12V standard lead-acid batteries by measuring the battery voltage, current and temperature.

“For cars with idle-stop-go function, this feature is mandatory to retain sufficient battery energy for a guaranteed engine start,” the engineering rep added. “Combined with the Atmel ATA6870 Li-ion battery monitor IC, it forms an ideal system solution for replacing 12V standard lead-acid batteries with Li-ion batteries.”

Additional key features of an Atmel-powered battery management system and components include:

• Active balancing – The industry’s first to feature active cell balancing for high cell count Li-ion batteries to prevent energy loss.
• Maximum safety – Highest accuracy due to simultaneous cell voltage measurement of the cells in the entire battery stack leading to precise state-of-charge and state-of health calculations.
• Smart sensing – Allows engineers to measure the battery voltage, current and temperature with up to 18-bit accuracy.
• Valuable development tools – PC-controlled development kits help devs easily build a battery management system and get the most of the battery management devices.

Interested in learning more? Detailed information about using Atmel’s powered system can be found here.

A closer look at Atmel’s vehicle portfolio

Earlier this morning, Atmel announced the expansion of an already formidable automotive maXTouch lineup with the mXT336S (optimized for 7-inch touchscreens) and mXT224S (targeted at smaller touchscreens and tablets).

In addition to touchscreens, Atmel boasts an extensive automotive ecosystem that meets strict quality demands, helping to make vehicles more safe and affordable. Primary solutions include battery management (Li-ion), car access, radio, networking, motor control systems and microcontrollers.

As previously discussed on Bits & Pieces, Atmel’s versatile AVR microcontrollers deliver power, performance and flexibility – making them appropriate for a wide range of automotive applications.

So what differentiates AVR microcontrollers from the competition in the automotive sphere? Well, according to an engineering rep, Atmel offers functionality and high temperature capabilities in its vehicle-oriented chip designs.

“Plus, complete system-in-package (SIP) solutions integrate components such as an AVR microcontroller, LIN and CAN interfaces, voltage regulator, watchdog, floating point unit (FPU), FlashVault code protection, high-speed Ethernet and USB with OTG connectivity in a single cost-effective package,” the engineering rep told Bits & Pieces. “In fact, Atmel’s highly integrated designs can reduce system costs by up to 60 percent, while saving time in development, integration and prototyping.”

Key specs include:

• High performance – Executing powerful instructions in a single clock cycle, Atmel’s 8-bit automotive AVR MCUs achieve throughputs approaching 1 MIPS per MHz, balancing power consumption with processing speed.
• Code protection – Atmel FlashVault allows devs to partially program and lock flash memory for secure on-chip storage. Code stored in FlashVault will execute as normal, but cannot be read, copied or debugged. It is also capable of carrying software such as math libraries or encryption algorithms to potentially untrustworthy environments where the rest of the source code can be developed and debugged.
• Built-in voltage protection – The on-chip voltage regulator with short-circuit monitoring interface featured in several 8-bit microcontrollers ensures reliable operation and extends the useful life of the device and the product it controls.
• Optimized power efficiency – Thanks to more than a decade of research, Atmel picoPower technology reduces microcontroller power usage in both sleep and active mode to achieve the industry’s lowest power consumption numbers.

Interested in learning more? Additional information about Atmel’s expansive automotive portfolio is available here and here.