Wang tiles made from DNA (using bases to encode the "colours", so matching up base pairs enforces the rules) have been used to perform computation.

AFAIK it's not yet a practical tool, but the choice of Wang tiles was practical for the experimenters since they're known to be Turing complete, and hence make for a more compelling demonstration.

http://www.dna.caltech.edu/Papers/FOE_2003_final.pdf