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Medical Electronics: Put All the Functionality in the IC

My colleague, Steve Taranovich, just wrote a blog on implantable medical devices: Let’s Chat: Medical Implantable Electronics Integration. He examined the challenges in designing such devices and the challenges related to the ICs that would be required to make such devices practical. I like to push into that topic a bit more.

We'll make a few assumptions to simplify this discussion. We'll add a caveat first. We'll go a bit beyond implantable and consider devices that are temporarily put in the body. This would include the miniature cameras that are packaged in an oversized capsule and swallowed.

Any device that is implantable or introduced into the body is there to monitor some aspect of the biological system that is human. So, there are parameters like temperature, pressure, flow rate, the presence of certain gases or chemicals, the pH level… the list goes on. That means we will need lots of sensors. They must be tiny, accurate, and low-power. Then we need to process these signals and establish a communications link to the outside world. Obviously, we're not thinking in terms of an RS232 or USB link. Instead, some sort of wireless link would be used.

What functionality do we need to have in an IC to do this?

  • Op amps — very low bias and offset; very low noise; temperature stable
  • Instrumentation amps — as above
  • Transimpedance amps — as above
  • Programmable gain amp — as above
  • Voltage reference(s) — accurate and temperature stable
  • ADC — 12 to 24 bits (so maybe delta-sigma)
  • DAC — 12 to 18 bits
  • Real-time clock — accurate and temperature stable
  • Microcontroller unit
  • Memory — volatile and nonvolatile
  • RF transceiver
  • Inductive loop transceiver
  • Voltage regulators — switchers and linear
  • Watchdog timer/supply voltage monitor
  • Optional — the actual sensor/transducer

Steve looked at the big picture for making devices to assist (or even replace) organs. I tend to look more at the “nuts-and-bolts” of the design. I'm considering whether we can do everything on my list in the form of one IC.

Can it be done? Can we make devices that draw miniscule amounts of power and still do what's needed? Can we design a wireless (RF or simple inductive) link to pass the data through the body tissue? Let us know. Comment here or come to our chat session next week.

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24 comments on “Medical Electronics: Put All the Functionality in the IC

  1. Davidled
    September 12, 2013

    This might be off topic. I think that package is also a portion of components in the device view point. Package strength and adhesive might be discussed in the medical device, because package including IC affects either body or skin and device performance is possibly degraded in the course of time, due the stress or aging.

  2. eafpres
    September 13, 2013

    Maybe you can do it with the MCU, but you are going to need a smart power management system to shut everything down between tasks to incrase battery life.  I think you also may need to control some sort of pump or infusion device or who knows what they might want to do with such a thing.

    Oh, and don't forget the miniaturized crew to go along with the device to keep it on course and fight off white blood cells.

  3. Davidled
    September 13, 2013

    Battery Life

    There are so many articles for battery life extension related to implantable medical device in the conference or academic journal. We all know that technology is amazing. I am wondering if these kinds of methods are truly validated in the medical clinic viewpoint.

  4. Netcrawl
    September 13, 2013

    @Brad that was great thanks for sharing it. Power supply is a big issue here, power supply in implantable device is generally divided into two components – power consumed by the output load, which can be the stimulated tissue delivering the drug, and the remaining power consumed by the ICs. In some cases the engineer or designer does not have any control over the load power, power saving efforts should be used toward minimizing the power consumption of the ICs. 

  5. Netcrawl
    September 13, 2013

    Daej good point! Packaging electronics, that's another big issue in implantable device. This is one strict requirement for all implantable electronics, packaging need to provide a hermetic seal to prevent any leakage of body fluids into the ICs and also protect body tissues from electronic materials, package should be biocompatible over its lifetime inside the body, we're talking tissue here very sensitive one , so packaging is always a top priority. Body fluids is very corrosive so we need some good protection in term of packaging 

  6. RedDerek
    September 15, 2013

    I see another need is for the device to be a throw-away. I do not see something that went through someone's digestive track to be reused.

    If anyone is taking a survey of needed devices, I would like to suggest a colon scanner. It would surely beat the current method. I am talking about the exam side. Once something is found, the traditional method may be needed.

  7. etnapowers
    September 18, 2013

    The sensors may be non ivasive, for example a smart test point to perform a check of the blood composition , by screening a small quantity of blood upon request.

  8. etnapowers
    September 18, 2013

    For sure the sensors should be first validated by a certified medical team and  then connected for example trough a wireless network to a database situated in a medical center

  9. etnapowers
    September 18, 2013

    The sensor inside the human body has to be accessible or replaceable , in case of failure or malfunctioning this is a important feature.

  10. Davidled
    September 18, 2013

    Typically, in the implantable medical device, if sensor might be replaced in case, this is a huge defect. I do not think that this type situation could be possible in real word. I believed that sensor is highly integrated inside device and should be fully validated in the viewpoint of clinic before it is released in the market.

     

  11. jkvasan
    September 19, 2013

    Transient Electronics as discussed in “Transient Electronics: Medical Devices Packaged to Die” can provide a solution to many challenges posed by implants.

    Getting the electronics out of the system without trace is a great subject and could be real in coming days.

  12. etnapowers
    September 19, 2013

    This is true for sure , but a failure is ever possible so i think this event has to be predicted and this is very important considering the importance of the reliability in this kind of application. 

  13. etnapowers
    September 19, 2013

    @JAYARAMAN: this is a great idea! I fully agree with this solution, it's less invasive and it can be controlled.

  14. kvasan
    September 23, 2013

    etnapowers,

    Though this seems exciting, the technology is far from actual practical implementation, may be a decade away. But then, this is always true at the start for any path-breaking technology from smartphones to satellites. Engineering is growing leaps and bounds and miniaturiation has become the buzzword. These devices may be in the market sooner than expected as various research groups are keen to find  solutions to the limitations of this technology.

  15. jkvasan
    September 23, 2013

    etnapowers,

    Though this seems exciting, the technology is far from actual practical implementation, may be a decade away. But then, this is always true at the start for any path-breaking technology from smartphones to satellites. Engineering is growing leaps and bounds and miniaturiation has become the buzzword. These devices may be in the market sooner than expected as various research groups are keen to find  solutions to the limitations of this technology.

  16. Vishal Prajapati
    September 23, 2013

    @BA, if all the things that you have listed would be accomodated inside a single device or IC, it would be universal device which can be used in almost all the applications, from metering, medical implants, wireless sensor networks, industrial telemetry, access control, etc. It is like jack of all.

  17. Brad_Albing
    September 26, 2013

    @eafpres – sounds like the plot to a science fiction movie – starring Blaine Bateman and Raquel Welch.

  18. Brad_Albing
    September 26, 2013

    @RedDerek – that can be done now as a virtual colonoscopy via a high-res CT scan. But it can miss things. So, combine that with one of the cameras-in-a-capsule that you swallow, and you'd pro'ly get a pretty good view with minimal discomfort.

  19. Brad_Albing
    September 26, 2013

    @VP – yes, that's the idea here. If the IC were used in a lot of different applications, that would drive the cost way down.

  20. Brad_Albing
    September 30, 2013

    @DaeJ – It might be slightly off topic – not that we mind, as it's always good to touch on these related issues – good dialog often results and we learn things. Altho' I'm not sure if we have anyone here who knows about the issues you mentioned.

  21. Brad_Albing
    September 30, 2013

    @etnapowers – Sensor failure is possible, but all the medical electronics is extremely high-reliability. There are stringent FDA standards that regulate these devices.

  22. etnapowers
    October 25, 2013

    @Vishal: good point, the main issue to solve in a general purpose device is the matching with a specific patient requirements, for example a patient could require a set of sensors that can exceed the capability of the general purpose jack

  23. etnapowers
    October 25, 2013

    Brad, this is true,  the medical electronics have to require the stringent FDA standards, but an engineer has to take into account the worst case that is a failure.

     

  24. etnapowers
    November 22, 2013

    @ Kvasan , I think that a decade can be considered as a very new technology normal time interval to become mature. Research groups will find solutions to the limitations of this technology only if the industries trends are in the direction of transient electronics, and I'm sure that this will happen!

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