Some Thoughts on MEMS in the Human Body

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"Micro-electromechanical systems (MEMS) is a technology that combines computers with tiny mechanical devices such as sensors, valves, gears, mirrors, and actuators embedded in semiconductor chips. Paul Saffo of the Institute for the Future in Palo Alto, California, believes MEMS or what he calls analog computing will be "the foundational technology of the next decade." MEMS is also sometimes called smart matter.

MEMS are already used as accelerometers in automobile air-bags. They've replaced a less reliable device at lower cost and show promise of being able to inflate a bag not only on the basis of sensed deceleration but also on the basis of the size of the person they are protecting. Basically, a MEMS device contains micro-circuitry on a tiny silicon chip into which some mechanical device such as a mirror or a sensor has been manufactured. Potentially, such chips can be built in large quantities at low cost, making them cost-effective for many uses.

Among the presently available uses of MEMS or those under study are:

• Global position system sensors that can be included with courier parcels for constant tracking and that can also sense parcel treatment en route
• Sensors built into the fabric of an airplane wing so that it can sense and react to air flow by changing the wing surface resistance; effectively creating a myriad of tiny wing flaps
• Optical switching devices that can switch light signals over different paths at 20-nanosecond switching speeds
• Sensor-driven heating and cooling systems that dramatically improve energy savings
• Building supports with imbedded sensors that can alter the flexibility properties of a material based on atmospheric stress sensing

Saffo distinguishes between sensor-effector type microcomputing (which he calls "MEMS") and micro-devices containing gears, mirrors, valves, and other parts (which he calls "micro-machines")."

My Thoughts:

MEMS devices will probably start being brought into the human body for therapeutic purposes before too long. How will they send data out of the body? MEMS devices could be organized in a network similar to the servers on the Internet. Each device would be capable of short range transmission. The data of the message would be divided into packets like the IP (Internet Protocol) packets. Packets would move randomly through the system until they reached the destination, possibly some kind of data collection device embedded under the skin. Presumably, the data from this device could be read without the direct contact of a port containing bare metal contacts. I presume this for aesthetic reasons---the preference of the patient. Data transfer could be done via RF transmission, possibly utilizing a passive RF circuit similar to those used anti-theft devices and stores. Perhaps data transmission could be done electromagnetically. However, I can't recall reading about data transmission based on this principle---only power transmission.

MEMS devices could be powered by electrical potentials inside the body. I believe devices powered in this way have already been developed, just for demonstration purposes at this point. However, I'm not sure about that, it may have only been speculation. MEMS devices could be composed of very small modules interconnected by biodegradable connectors. That way, the MEMS device would essentially dissolve after a set period of time and be expelled from the body in the urine or feces. I can't imagine that people would want to have this kind of stuff accumulating inside their bodies over time. This leads to an idea for another type of data collection. The MEMS devices could place the data into small capsules designed to be flushed out of the body with the urine. The patient would need to urinate into a receptacle handed over to his or her doctor. There could be redundancy of messages to cover the times when the patient was urinating away from home.

The introduced of MEMS devices into the human body seems quite likely to me. Currently, scientific understanding of disease is advancing and many of the specific mechanisms involved with disease are becoming better understood. For example, microphages, cells inside the bodies of animals that are part of the immune system and that are designed to "eat" bacteria and other small living things, have now been shown to sometimes play a key role in the development of cancer. (This example comes from a recent scientific American article.)

The evidence relates to one of the breeds of mice that has been genetically developed to regularly create cancer inside themselves. It was found that destroying the microphages of this mouse prevented it from developing cancer. Precancerous cells were developed as is normal for this mouse, but they could not convert into cancer.

The microphages are normally controlled by chemical signals created by the mouse's body. However, it now appears that some cancer cells have evolved a way to send bogus chemical signals to the microphages and hijack them. The microphages then play key role in converting precancerous cells into cancer. Killing the microphages in the mouse inhibits the final development of the cancer.

When one considers complex mechanisms like this that are involved in the creation of diseases, one can see the advantage of incorporating MEMS into the body to monitor highly localized processes. Of course, there would need to be some way of knowing where particular pieces of data came from in the body. One way to do this would be to somehow anchor each MEMS into a permanent, known position in the body. Then the doctor would be able to locate the origin of the data from the MEMS's own ID tag which would be included in each piece of data. However, anchoring a MEMS in the body does not sound very easy. Perhaps each MEMS could have a tropism for a particular biochemical environment located at a particular place in the body.