Expanding contracting material to create black dot

I am looking for a material that can easily contract and shrink to create an effect of a black dot with varying diameter using a small
heat source. The idea is to get a drop to expand to a specified diameter using electricity. Any other suggestions for achieving the same effect will be welcome. thanks, Oren.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Have you looked at piezoelectric elastomers? They can have enormous deformation from an applied field Here's one link - it's the wrong way round (generator mode) but it's a start. www.erg.sri.com/publications/PelrineSPIE2001.pdf
Gregg
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Polytechforum.com is a website by engineers for engineers. It is not affiliated with any of manufacturers or vendors discussed here. All logos and trade names are the property of their respective owners.