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Live Mite Riding MEMS Device: 

The Full Story

AVI File

OK, so you are interested in the whole sorted story of how we got dust mites to ride on our MEMS device. I will reveal for the first time ever the whole story of WHY we did it and HOW we did it.  It was in the mid-1990's and many people at the time were saying that MEMS would never be able to do any useful functions.  People working on MEMS were accused of "playing in the sandbox" and of being "dreamers".  In particular, work  on complex motors and so forth was scorned.  At one conference a respected professor stood up and said in disgust that MEMS really stood for "Micro Engines Move Squat".  Indicating his opinion that MEMS work focused on complex mechanical elements would never amount to anything.  At the time, we were struggling to get even the most simple mechanical functions working.  Well, we took the "Micro Engines Move Squat" comment as a direct challenge, and we purposed ourselves to show that MEMS devices could indeed move real mechanical loads, and therefore, would in fact some day find significant and relevant applications.  But at the moment, the goal was to show that MEMS could move real loads. Now the question at hand was, what would be a relevant demonstration.  We considered several things like salt (too boring), blood (too messy), or hair (wrong shape).  In the end, we decided the most impressive demonstration would be to get a live spider mite to crawl up on the device, and then give him a ride around.  This demonstration also gave us the opportunity to respond to the respected professor the following year, that in fact, MEMS stood for "Micro Engines Move Spider mites".

So, we set about to do the demonstration.  Immediately, it turned out to be a lot harder than we had imagined.  The first problem was finding mites in New Mexico.  Apparently, mites love damp, moist environments, something hard to find in New Mexico. The next problem we found was that mites come in many different sizes . . . some too small and some too large for our MEMS device.  The other problem we found was than some mites are transparent under the the bright light of the optical microscope.  So, we needed a special mite . . . one not too large, and not too small, and one with a thick skin so he would show up nicely under the microscope.  It was clear that we were quickly getting out of our area of expertise, so we decided to find an entomologist to help us.  We called around at a nearby university and found that there was actually one of the world's premier mite experts right down the street from us.  We contacted him and he agreed to help us in our endeavor to find the perfect mite.  He said that he had the perfect place to "catch them" and if we would send someone to meet him at 10:00 PM, he would help to track down the illusive critter.

Well, we immediately put Glenn, one of our top technicians, on the job, and gave him the contact information for our newly found entomologist friend. Glenn met the good bug doctor at his office at the specified time.  He told Glenn that he had a special place for catching the mites.  So, he piled Glenn in his car and started driving.  After some time they pulled into a deserted area.  Glen became a little uncomfortable when he realized that the guy had driven him to a remote grave yard. Sensing Glenn's discomfort, he quickly explained that the graveyard was the perfect place to catch the particular species of mite we were looking for because they water the grass there a lot, creating the moist environment the mites crave.  At the same time, the grave yard had much less foot traffic than, say, a golf course,  so the mite colonies can grow relatively undisturbed.

They wander around the grave yard, and at about the stroke of midnight, the bug man finally finds the perfect spot, and sets his traps.  Yes folks, there are such things as special purpose dust mite traps.

They find a comfortable spot nearby to sit, and the bug man then proceeds to tell Glenn more than he ever wished to know about mites . . . not just any mites, but the particular type of mites that were the perfect size and opaqueness for our project.  The man explained that dust mites live for only a short period of time, so to be successful, we would have to host our own colony, ensuring we would have live specimens to take the wild ride on the MEMS device.  Glenn learned that a miniature rose bush would be the perfect venue for hosting the colony.  The man explained it was critical to mist the small bush several times a day in order to maintain the humidity necessary for the colony to thrive.  After several hours on the proper care and feeding of the new colony, they determined that there would be a good starter set of mites in the trap, so they retrieved the trap, just as the sun was beginning to rise over the horizon.

Glenn showed up in the lab the next morning at about 7:00 AM.  In his hand was a miniature rose bush in a small pot, teaming with our colony of perfectly sized and tinted mites.  The mite colony . . . I mean rose bush was placed in the test lab, and we now had the specimens we needed to make the above video.  However, at the time we did not have any MEMS of the proper size and power for the desired demonstration.  Within about a month, some new devices came out of the fab.  Devices with the perfect size and power to give the mites a ride.  It was during this period of time that several technicians working in this lab developed a peculiar and unexplained scalp irritation.  

Then came the moment . . . we had the bugs, we had the MEMS, but how to get the bugs to crawl up on the MEMS and take a ride.  Our first try was to simply shake the rose bush over the wafer, and have an army of mite paratroopers invade the surface of the wafer.  This worked, but after several hours of staring at the microscope, we found that the mites were running all over the place, but none of them happened to crawl up on the particular MEMS device we had up and ready to run and under the camera.  

Those of you who have done any testing of wafer level microelectronics know what probes and micromanipulators are.  They are the precise alignment devices that allow you to bring electrical signals onto the surface of a wafer to test microelectronics in wafer form.  To the microelectronics engineer, they are the valuable tools that allow this important testing to be done . . . . to us they became micro-cattle-prods for the purpose of "herding" the mites where we wanted them to go.  We found that we did not have to energize the probes with high voltages like you do with traditional cattle prods, but rest assured we were prepared to should it become necessary in order to get the shot.  Simply nudging the mites with the probes provided the mechanical stimulation needed to get the mites to go where we wanted them to.  After perfecting the art of mite wrangling, the big day came to make the video.  It was a Saturday, since we would never dream of doing this work on company time.  We had a guy to run the video camera, we had Glenn, the mite wrangler, and we had someone to run the MEMS.  Everything was ready, so Glenn shook the miniature rose bush over the wafer, and sure enough got a really nice herd smack in the middle of the wafer.  As they made their way across the wafer, Glenn spotted one particularly lively mite on the outskirts of the herd.  At about the time the herd was approaching the MEMS mirrors, Glenn skillfully brought the probe tip around and cut the lively mite from the herd. Immediately, the mite made a b-line towards the optical shutters, but Glenn headed him off at the pass, and nudged him back in the direction of the gear we were shooting for.   With success within site, the camera was turned on, and within seconds, the mite crawled up on the MEMS gear.  Immediately, the MEMS was turned on. The mite was startled, and stopped walking.  He stood on the gear, as the MEMS spun up to several thousand RPM.  After five or six seconds, the MEMS was turned off, and the mite was temporarily disoriented.  After a minute or two, the mite regained his sense of direction, and scurried off to join the rest of the herd, which by this time was over by the MEMS accelerometers on the upper quadrant of the wafer.

The wafer was then shaken over the top of the rose bush to return the mite colony to their home.

The colony survived on the rose bush for several years in the lab.  We periodically would borrow a few for various pictures as new devices came out.  In about 1997 the mite colony became so populous that they actually killed the rose bush.  Losing their source of sustenance and protection, the colony died.  It was about that time that the mysterious scalp ailments of the people working in the lab cleared up.

Since that time, the video of the mite has been featured on television shows around the world, including the ABC evening news with Peter Jennings, CNN, Discovery Channel, and the NBC nightly news. And now you know the whole story of how it was done.

 

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paul.mcwhorter@memx.com

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