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

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