Piezoelectric material for linear positioning - Page 1
Forum section: electronics / projects

author: rossmoffett
author_rank: Regular Contributor
timestamp: November 12, 2012, 05:50:30 am
content: I wonder if anyone here knows where I could source piezoelectric material, the sort used for positioning in atomic force and scanning tunneling microscopes.A lot of hobby projects cut piezo disks (such as used in tweeters) into four sectors, likethe one described hereand use them as positioners. I'd like to build something more similar to the XYZ positioners in commercial units, but have no idea where to source the raw chunks of piezoelectric material I'd need for that.I have found some lab supply companies that will source it for god-awful amounts of cash, but I know there must be some supplier selling it for peanuts since some of them are naturally occurring materials and most forms are under mass manufacture.

author: XynxNet
author_rank: Regular Contributor
timestamp: November 12, 2012, 07:09:12 pm
content: This site might be interesting for you:http://sxm4.uni-muenster.de/stm-de/It is in german, but maybe google can tranlate it in a usable way.They source their piezos fromhttp://www.piezomechanik.com/en/home/introduction/index.htmlThe university also resells 3 piezos for ~130€.

author: rossmoffett
author_rank: Regular Contributor
timestamp: November 12, 2012, 10:59:51 pm
content: Hey, thanks a bunch XynxNet. I saw the university site, but couldn't figure out who their vendor was. That was posted on Slashdot some time ago and I've been wondering ever since. I feel the price is a bit steep for a few chunks of mass-produced crystal. Not as bad as the Veeco positioning stage I once replaced, which had a cost of $3500 USD assembled! After that, everyone was ultra-careful when moving the atomic force microscope around.There's in fact a whole lot of info on the web concerning DIY STMs now. Back when I first wanted to do this, I had three sites, nowthere's a plethora of information.

author: mrflibble
author_rank: Super Contributor
timestamp: November 14, 2012, 08:02:12 pm
content: Quote from: rossmoffett on November 12, 2012, 05:50:30 amDid you find an affordable alternative yet? Because same as you, the only affordable option I found so far is the piezo in 4 quadrants option....

author: ejeffrey
author_rank: Super Contributor
timestamp: November 15, 2012, 07:43:48 am
content: I've bought some piezo elements from noliac and been pretty happy with them. They aren't cheap but they aren't PI/Veeco expensive. I do think they have minimum order quantities.Honestly, a lot of this stuff is low volume, even many of the 'standard' products. Even if you are buying something that is produced in high quantity for a commercial customer, you aren't likely to find manufacturers selling one-offs at prices we are used to seeing for off-the-shelf electronics. Re-purposing a common element like a piezo buzzer or finding over-stock / salvage parts is probably still your best option.

author: rossmoffett
author_rank: Regular Contributor
timestamp: November 15, 2012, 09:07:40 pm
content: I've found some US suppliers of piezo material, haven't requested quotes yet.The four quadrant option bugs me because of the lack of rigidity in everything leading up to the probe point, doesn't seem like it's easy to replace the STM tip (which wears out often during use) and it also doesn't fit well with AFM type cantilever elements. I'm considering going with the German universities method of three piezo elements, one for each dimension, but using the cheaply available commodity piezo disks. That would at least allow for a more rigid probe mount, but piezo disks have poor travel distance. Oh well, can't have everything in a home-made nanoscope..

author: mrflibble
author_rank: Super Contributor
timestamp: November 15, 2012, 09:26:12 pm
content: It's been quite some time since I last looked into all of this.... The EUR 124 for a set of three is a whole lot less than what I could find years ago.As for using 3 piezo discs, I suspect that you will get pretty poor max. stroke. Definitely not anything in the 5 micrometer range like that PSt 150. Plus an even lower resonant frequency, so lower scanning frequencies. And as for damaging tips ... yeah I would count on that.which is why you'd put a tip holder on the piezo disc. Bonk the tip into the surface, take tip out of holder and put in a new one.

author: rossmoffett
author_rank: Regular Contributor
timestamp: November 15, 2012, 09:42:18 pm
content: Just for point of discussion I've used a Nanosurf easyscan 2 STM, Nanosurf easyscan 2 AFM and Veeco AFM extensively.Someone at the university broke the piezo assembly of the Veeco AFM once, which is how I know the commercial cost was north of $3k USD for the replacement assembly (I installed it). I think it was still $1500 USD or thereabouts when we applied an educational discount. So yeah, in that light, EUR 124 is a great price for the elements.I'd still like to see if something better is available. If quantity discounts could get the cost for three sensors down to $10/ea or so I might even buy bulk and sell kits or something to make up the cost. I'm really interested in getting one of these machines running to do some research in my home lab, and it would be cool to make it a more available tool to the general public with the cheapest STM on the market being $8000 USD.The big problem I see with the quadrant is mostly that it isn't rigid, so there's going to be a lot of unwanted oscillation in the tip unless it's run very slowly. I also suspect that it would be very, very delicate while replacing tips. I had to make a new one approximately every 30-60 minutes of use, depending on what I was looking at and how much I crashed into the sample.That said, if single stages of elements are only good for 100 nm or so of travel I'd be fine with that, for what I want to do. It's always possible to stack them too, at $0.30 USD each that's not going to break the bank even if ten are needed per axis. I have a bunch of these already, maybe I'll do some experiments using a micrometer to see what sort of travel can be expected when I return from my trips in a couple of weeks.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: November 27, 2012, 06:15:23 am
content: In another life I used to build STM/AFMs at Burleigh Instruments, now long gone. When you consider the environmental grief and other things a pzt manufacturer has to go through, the price they charge makes sense. I'd be looking at surplus disks for ultrasonic cleaners, or even buying replacement disks and cutting them up (only wet to control the lead-containing dust). There's also some info on the 'net about making your own Rochelle salt crystals for piezoelectric experiments. We used to use medium wall tubes, with segmented electrodes so the tube would bend in X and Y. They were expensive and had to be scanned slowly. It's possible to bury a ball bearing in some Sorbothane at the top to provide damping, which reduces ringing on reversal.Something I've always thought interesting is that even back in the 1930s it would have been possible to build a functioning STM using vacuum tubes and a long persistence phosphor tube for the display. There is no technology in these things that's particularly hard to do. AFM is a bit of a pain because you need cantilevers and can't easily make them. STM electrodes are pretty trivial if you can get some platinum-iridium wire. HOPG makes a good target to start with. The preamp circuit is also quite easy given the quality of op-amps available now. I'm only here now and then so feel free to visit my website where you'll find my email address.http://www.conradhoffman.com