Implementation of Digital\nComputing by Colloidal Crystal\nEngineering with DNA

Toehold-mediated strand displacement (TMSD) provides\na versatile\ntoolbox for developing DNA digital computing systems. Although different\nlogic circuits with diverse functions have achieved good performance\nin terms of complexity and scalability, most previous DNA logic circuits\nperform information processing only at the molecular level, and nonspecific\nsignal leakages are often difficult to avoid. Here, we demonstrate\nthe feasibility of constructing leakless digital computing systems\nin three-dimensionally ordered colloidal supercrystals. These systems\npossess a unique signal leakage resistance by integrating different\nTMSD-based logic gates with the catalytic assembly of DNA-functionalized\ngold colloids. A complete set of basic Boolean logic gates and different\ncascaded logic circuits is constructed on the basis of the catalytic\nassembly strategy enabled by a facilely designed catassembler, where\nthe output signals are recognized by determining whether specific\ncolloidal supercrystals are formed or not. In addition, a half adder\nis built through a combination of XOR and AND logic gates with two\ndistinct crystal types as readouts. Finally, a leakless two-digit\nDNA keypad lock for information security protection is demonstrated.\nThe combination of TMSD-based logic circuits with the universal nanoparticle\ncatalytic assembly offers the possibility to develop highly complicated\nand leakage-free digital computing systems and promotes macroscopic\ncolloidal superlattice materials with programmable logic functions.