Tiny, Implantable Medical Device Can Propel Itself Through Bloodstream


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Someday, your doctor may turn to you and say, "Take two surgeons and call me in the morning." If that day arrives, you may just have Ada Poon to thank.

Yesterday, at the International Solid-State Circuits Conference (ISSCC) before an audience of her peers, electrical engineer Poon demonstrated a tiny, wirelessly powered, self-propelled medical device capable of controlled motion through a fluid—blood more specifically. The era of swallow-the-surgeon medical care may no longer be the stuff of science fiction.

Poon is an assistant professor at the Stanford School of Engineering. She is developing a new class of medical devices that can be implanted or injected into the human body and powered wirelessly using electromagnetic radio waves. No batteries to wear out. No cables to provide power.

"Such devices could revolutionize medical technology," said Poon. "Applications include everything from diagnostics to minimally invasive surgeries."


This is a great research by engineers at Stanford University. Making tiny implantable devices, which can easily run through the bloodstream that too without wires or batteries are really commendable. New medical devices such as cochlear implants, heart probes, drug pumps etc. can remain stationary within the body. Well the idea of making such devices was not new, but its proper implementation has given them a great success.
How do they remove them? What if they quit working what becomes of them, wouldn't they create a blockage or rupture a vein or artery?
I spent ~20 years in APL/JHU's space department, but more than half my efforts were biomedical / implanted devices being half of that half. Our first implant about 40 years ago was a heart pacer which used very advanced rechargeable batteries (like we put into space craft). Once each week the user wore a vest while sitting in a chair for about an hour. The box that drove the magnet field also recorded information about heart rhythms etc. It was made with the same rigorous quality control as items we sent into space - far more reliable than any other heart pacer on the market, but doctors did not like it. They liked the several hundred dollar fees they got every two or less years for a minor operation that replaced the expendable battery located beneath the skin of the stomach.

Our next implant was called AID (Automatic Implantable Defibulator - not the best name in view of the disease soon to be called that too.) for a much smaller market. Then came the implantable insulin pump, which you can still buy from MedTronics. Rechargable batter lifes greatly improved and huge reduction in power required for the electronics occurred, so APL/JHU highest reliability on the market "space department quality control & reliability" pacer system with very advanced monitoring telemetry was also licesened to MedTronics. Most patients will die before the battery does and the telemetry give more than a year of warning before it will die.

We were never able to make a blood sugar sensor that would work for more than a few months, so the insulin pump runs "open loop." I.e. the user's control commands how much to release based on what he is eating. The chamber that stores very concentrated insulin last for a few months between refills. For safety (a strong dose of insulin kills) its pressure is less than atmospheric. AFAIK none have ever leaked but if one did, the flow would be body fluids into the pump.

We also made a lot of devices and electrode arrays for use by neurosurgeons treading "sever chronic pain." They tried what could be call "electrical acupuncture" with currents driven thru the "dura" surrounding the spinal cord. That requires much more energy than just triggering the heart beat does, so rechargeable batteries were needed or more commonly just intermitted energizing of the electrodes was tried.

I was several times in the OR while the electrodes were implanted. Initially the doctors used the large needle they used for "spinal taps" as the wires from the electrode could slip up thru it. After they had punched thru the cartilage between two vertebra and had located the electrode on the dura, they would pull the needle out and then try to make a good solder joint between the two leads and a small electrical plug (or the wires from the much larger "pick-up" coil to remain in the abdomen. I watched, silently but in horror them drop tiny balls of hot solder into the patient as this connection was made in the OR.

I rapidly made an new needle for them at APL which did not need to be pulled back over the leads to leave thosee wires out side of the needle as my needle came apart side wise - was two U shaped channels one slightly smaller than the other so it could fit inside the larger one. APL/JHU, not me, owns the patent on my "splitable needle."

Space craft technology is very similar to that needed for implantable devices as both need:
light weight / small sizes
low power to operate
Extreme quality control (you don't get to "go there" and repair)
Remote RF control
telemetry telling how it is operating (or what is the problem if it is not)
Affordable cost - more important for mass produced implantable devices than NASA.
Resistance to an environment that is actively trying to destroy the device.

So it Is natural that APL/JHU space department, with its close connection the world leading JHU hospital, should have not only designed more than 200 space craft that were launched but be a leader in implantable medical devices as well. I have also assisted one JHU neurosurgeon in his primate lab (~50 rhesus monkeys) in two major studies. Held a human brain in my hands and once when near end of an brain operation he was doing with me assisting he was called back to he hospital as an accident victim with sever head trauma was ho his way to the ER and he was the "on-call" neurosurgeon that late eve. I finished small part of the procedure and closed up - the money lived OK except for the damage we intentionally did to it. Monkeys do not naturally have epilepsy* so the their first operation was to cause it by damage to the motor cortex - we needed to be able to observe the seizures to evaluate various "cures." Only about one in three of our "preparations" would result in a monkey that had four or more seizures with useful statically regularity for testing "curative procedures / drugs."

I have been involved in several other implant device development effors too - one failed as we could never made and artificial sphincter to be an essential part of a urinary control system for the VA. More than 1/3 of their long term paraplegic patients die of kidney failure as they have no control over urination - the automatic discharge mode only empties a small fraction of the urine when the pressure is bladder dangerously high. Thus, there is "back-flow" into the kidney and many kidney infections - one of which usually does kill ~1/3 of their patients. We killed quite a few rabbits before giving up. Every version of a commandable sphincter we tried caused necrosis of the urethra as the closing pressure was on it > 95 % of the time.

Another project was for the WHO, which had a serious problem with syringes being stolen and repeatedly being used for a small fee to inject creek water into ignorant people who believed it was the injection process that helped cure or protect them. My invention, a complex locking system would have worked to make only one use possible but would be nearly impossible to make via cheap injection molding. Fortunately for the WHO, a colleague of mine, knew about a certain cheap material are initially is porous but swell up to be solid after being water wet. - A simple thin disk at bottom of the syringe was "just what the doctor ordered" - and at insignificant additional cost.

Because of our connection with JHU hospital and long list of perfected biomedical device successes, many more than we could help suggested projects to us they needed help with. Both the US army and Navy independently came asking us to develop an artificial blood that did not need refrigeration. We said we were not experts in chemistry and were already very busy.

* Evolution has strongly selected against that - falling out of a tree during an epileptic seizure is not good for survival prospects.
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They would not block an artery, but sure might get stuck in a capillary....

Then what would happen to the human? If many of them were inserted wouldn't there be a possibility of many getting stuck? Then how can they remove them?
Then what would happen to the human? If many of them were inserted wouldn't there be a possibility of many getting stuck? Then how can they remove them?

Well theoretically they could be held together by a biodegradable glue, that would dissolve after a predetermined time.
Well theoretically they could be held together by a biodegradable glue, that would dissolve after a predetermined time.

The glue would dissolve but the chip wouldn't so again how are they going to remove them if they block a capillary?
If you make the chip of paper, it too would dissolve, this could be done.

But then it would dissolve very rapidly because paper and water, which blood is made up of, don't work well together and rapidly tears the paper apart.
But then it would dissolve very rapidly because paper and water, which blood is made up of, don't work well together and rapidly tears the paper apart.
Nah, the protective wax coating would be effective, for the short lifespan of the artery roto rooter or whatever the machine is for.... The process is viable, I do predict it in some fashion.
They should put be able to track it and be able to remove it if it does ever get stuck in anything before inserting it into anyone. If they can't this chip should not be injected into people for it could become stuck and cause serious problems.