IEEE IMS 2015 Chair Vijay Nair and VC Stephen Goodnick share insights on skin-based RF wearables, energy harvesting, 5G, mmWave, material science and more.
By John Blyler, Editorial Director
The plan was bold, namely, to bring the bio-medical and RF-microwave communities together to talk about the challenges of radio-enabled wearable devices. Was the plan successful? To answer this question and others, “IoT Embedded Systems” sat down with the IEEE IMS 2015 General Chair, Dr. Vijay Nair, and Vice Chair, Stephen Goodnick. The discussion covered not only the RF-Microwave IC side of bio-medicine but also touched on trends in material science, energy scavenging, near-threshold voltage, 5G, millimeter wave technologies and more. What follows are excerpts from that conversation. – JB
Blyler: Let’s start with the hot topics of RF energy scavenging and harvesting. Are we getting any closer to really enabling this technology?
Nair: There are several different ways in which energy scavenging is being pursued. One is the ambient collection from the air. The big debate is if you can get enough energy through that technique. Also, you can scavenge energy from your body as you move. This source will still very low power. The goal is to take some energy from here and there, then combine them.
RF scavenging is another technique. It is used to run applications where something is interrogated and activated. For example, in his Plenary session, Dr. Rogers demonstrated a device that was activated by sending Near-Field-Communication (NFC) power to his skin. The power was still very small and it required a big coil in the (transmitting) laptop. More research is needed in material technology to make a smaller gadget. For example, magnet or dielectric materials could provide smaller sized coils. (JB – Imec pic?)
Goodnick: Or instead of worn on the body, such technology could use temperature as one source or actually glucose harvesting from the blood stream or other things. The fuels we use in our body could be used to power integrated devices. (JB: Glucose – recall grape clock article and diff. between battery and fuel cell – mainly the later).
Blyler: Such ultra-low power energy harvesting approaches seems to go hand in hand with Near Threshold Devices (NTD).
Nair: Correct. The low power (NTD) devices get just enough power to turn on other devices. The goal is to activate the system as needed so the high-powered radio isn’t turned on all the time. Put another way, wearable technology should use average power consumption – not peak power. That way, radios use power only when needed to transmit something. It helps that SoC technology requires lower and lower power to run.
Blyler: Thanks to Moore’s Law. But Aart de Geus, the CEO of Synopsys, said at DVCon last January that Moore’s Law is only good for another 10 years.
Nair: Thirty years ago, Intel said the same thing, i.e., (Moore’s Law) will be there for 30 years but we can only see far enough out for the next 10 years.
Blyler: Let’s switch to another hot topic, namely, 5G. Many pundits talk about millimeter (mm) wave as being the enabler for 5G because of the requirements for big bandwidth, low power and high data rate. What’s happening in the 5G and mm-wave spaces?
Nair: The big challenge is that we still don’t have a standard for 5G. The frequency of operation is still not determined. But companies are still moving forward. They go ahead making semiconductor equipment to demonstrate how 5G might be implemented to the FCC. As more people (ecosystem partners) support a given implementation at a particular frequency band, it appears as if a 5G “system” is in place. This is how most standards work, by bringing one implementation of a technology to the FCC for approval. If convinced, then the FCC will issues a frequency band for that technology.
But we don’t know what the 5G frequency band might be – anywhere from 20 to 60 GHz. (Editor’s Note: These are the millimeter wave bands.) But the FCC has yet to define that band.
Blyler: What were you most excited about at this year’s IMS show?
Nair: We want to get more power in this smaller form factor that is mobile enough to take anywhere you want. Such devices would require lower-power SOCs and low power RF systems like Bluetooth and wireless LAN systems. Additional energy for this low power devices should be supplemented by energy scavengers to minimized battery use. But you still need a battery. Battery technology is another key area that needs innovation.
The main theme for this year’s conference was wearable, RF-enabled systems. The plenary keynote, the panel session and pavilion takes have all been on wearable, wireless systems
Goodnick: And it’s related to the theme of bio-medicine. How does our RF-Microwave community play in the emerging bio-medical space. Dr. Rogers talk during the plenary was more generally about bio-electronics and life sciences. Later on, Agilent discussed why they went from being a test and measurement (T&M) company to a life sciences one.
Blyler: Stretchable electronics play into the bio-medical space.
Nair: Indeed. That’s why Rogers talked about bendable polymer base to act as a substrate for the ICs. His example was about slices so you bend here and there while all the slices are connected using a flexible substrate. So it fits the contour of the body.
The idea is to use ultra-thin CMOS that is lifted off and placed on a substrate as a layer – for example, a SoI substrate. Then one can use a slice of it. The game changer is combining radios with stretchable substrate to enable wearable on the body.
Goodnick: That is why the plenary was given by a material scientist and not someone in the mainstream microwave community.
Nair: Another challenge is the antenna application. We all know how to design antennas, but once you put it on moveable, bendable skin, then the frequency of the antenna changes. To deal with these changing frequencies, you need to have adaptive systems – software intensive.
No one area will be able to handle all these issues. That’s why you need materials, electronics, Silicon, software and more. It all has to come together to make wireless wearables happen.