Sciencemadness Discussion Board

Filter paper that doesn't stretch

paulr1234 - 1-12-2010 at 23:33

Apologies for the somewhat crudely phrased subject line.

I'm doing some research into carbon-nanotube-based electroactive polymer actuators for robotics. A common preparation is to filter the CNT+polymer mixture through a filter paper, to then dry the resulting sheet leaving a CNT layer on one side and to then cut the material into strips. The electrostrictive contraction of the polymer layer on top of the inactive cellulose substrate then causes a bending motion.

Applying power to these materials only causes a small reduction in the carbon=carbon bonds which creates the actuation motion. The amounts are small, typically only 4%, so I am looking for some alternatives to ordinary filter paper, perhaps Tyvek or maybe borosilicate fibers with an inert binder.

I want to find a substrate that has the smallest possible tolerance when dry (e.g. will stretch or compress by the smallest amount possible, to maximize the potential bending of the EAP layer.

Most suppliers/manufacturers of specialist lab filter papers record all kinds of data (particle retention, flow rate, loading capacity even tensile strength) but I have yet to see anyone publish data on stretchability (I'm sure there's a better scientific term for this and I'd love to know it).

I was wondering whether anyone here had any thoughts on suitable materials.

Thx.

watson.fawkes - 2-12-2010 at 04:34

Quote: Originally posted by paulr1234  
stretchability (I'm sure there's a better scientific term for this and I'd love to know it).
For isotropic materials, it's Young's modulus.

matei - 2-12-2010 at 06:24

Inorganic membranes (such as the aluminium oxide membranes from Whatman) seem to be what you are looking for:

http://www.whatman.com/PRODAnoporeInorganicMembranes.aspx

They come in different porosities and diameters. However you need a special filtration device to hold the membrane, which is somewhat expensive.