Update README.md

README.md

@@ -5,6 +5,7 @@ and is linked to : https://tourlomousis.pages.cba.mit.edu/rheometer-cover.
 <h2> TO DO </h2>  
 - fix current microscope stage 
     - start with the mini linear axes | miniature flexible shaft couplings form SDP SI
+        - http://shop.sdp-si.com/catalog/product/?id=S50MSCMA12H04H04
     - adding linear rails - constraints
     - not side rails but lay them flat to maximiza load tolerance
     - add constraint pins to linear rails