let's talk about implants
i work in a lab that has mostly specialized in biologically inert non-fouling surfaces. basically, implants that don't need a workover every handful of years, and no need for blood thinners... i'm talking no rejection implants.
silicone is only good for some things and PEG/etc is no good, we all know that.
implants of any decent size usually require these things (cleaning / thinners) due to platelet / stuff attachment to their surfaces as the body tires to de-integrate with them.
do we have any chemists here? can anyone do click chemistry or ATRP grafting? if so, i have some interesting things for you guys to try out in your next implant attempt...
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Anything requiring greater process control than this would probably need to be jobbed out to a facility that applies such coatings. If you know of any grinder friendly facilities willing to do this for a reasonable price, please pass the word on about that too.
Thanks.
Bonus points galore if you can find, and coat, a bluetooth headset (or other small audio receiver) that also has built-in wireless/inductive charging. That would be a godsend to the community.
for testing out the efficiency of coatings i'd suggest using a dummy which also allows you to test the coating itself. like having a non toxic plate with markers for humidity on it.
this approach was mostly chosen for the availability of parts, ease of handling and the benefits for prototyping. as the implant will be removed after a certain time of implantation and taken apart for analysis.
guess the ptfe tubes or rods could be coated aswell, for experimentation purpose.
since no one is shaking his arms 200 times per second, or even 20k times/s. that's not entirely ruling out piezos as such, but it would require to come up with a design that compensates for those issues.
by increasing the available path a mass can move to several centimeters we'd be able to get away from high frequencies. the basic options would be either a tube with magnets sliding through it and a coil wound around it (like those shake-flashlights). or a magnet that rotates over a ring of coils (very similar to what mechanical self-winding wristwatches do).
the linear version is rather easy to build but in terms of power output i'd go with the rotating version as it picks up a wider range of motions.
construction of such a rotating generator is a lot more complicated and may even require micro-gears. so i'll leave this up to some dedicated precision engineer.
last but not least we have solar panels. if we keep the circuit boards single-sided. we could use the other side to directly mount solar panels to it. there are excellent circuits to help harvesting energy from low-power solar setups. for an implant location that's exposed to daylight/sunlight and rather close to the skin surface that's certainly an option worth trying out.
the design is a difficult question. a tube that runs in parallel with the bones would be probably be suboptimal since (my guess) most motion happens along the "thumbs-up" axis (of the arm/wrist).
getting some data on this would be very useful in optimizing such a generator.
so... to all smartpohne owners out there ( SMARTPHONES REQUESTED): please download some acceleromater logging app, attach the phone to your wrist/upperarm/torso/legs/wherever and log the data (whatever timeframe suits you). also please attach what axis the data correspond to.
like for the wrist: https://en.wikipedia.org/wiki/Right-hand_rule
i'll try a bit of logging myself with a wii controller i have around. the more data, the better.
http://home.arcor.de/positiveelectron/files/wiimote.jpg
slapped together a small python script logging it. if someone is interested i'll upload it. logs the data to a file, and allerts you with the pager motor in case the battery is near-empty (below 25% in my case)
install python and the python wiicd library. and
python logaccdata.py
press 1+2 on the wiimote as prompted on the terminal.
if it connects it should run a test on the rumble motor. then it should create a logfile with x,y,z data. dividing those values by 10 will get you the acceleration in m/s²
if the battery goes low it'll rumble you aware of it.