DNA molecules provide what is probably the most iconic example of self-replication—the ability of a system to replicate, or make copies of, itself. In living cells the process is mediated by enzymes and occurs autonomously, with the number of replicas increasing exponentially over time without the need for external manipulation. Self-replication has also been implemented with synthetic systems, including RNA enzymes designed to undergo self-sustained exponential amplification1, 2, 3, 4, 5. An exciting next step would be to use self-replication in materials fabrication, which requires robust and general systems capable of copying and amplifying functional materials or structures. Here we report a first development in this direction, using DNA tile motifs that can recognize and bind complementary tiles in a pre-programmed fashion. We first design tile motifs so they form a seven-tile seed sequence; then use the seeds to instruct the formation of a first generation of complementary seven-tile daughter sequences; and finally use the daughters to instruct the formation of seven-tile granddaughter sequences that are identical to the initial seed sequences. Considering that DNA is a functional material that can organize itself and other molecules into useful structures6, 7, 8, 9, 10, 11, 12, 13, our findings raise the tantalizing prospect that we may one day be able to realize self-replicating materials with various patterns or useful functions.
Figures at a glance
Figure 1: DNA tile sequences and structures. 
a, The P6HB motif, drawn with GIDEON24, comprising two BTX domains paired by four lateral connections. The cross-section view shows two of the four helices that are formed by the lateral cohesive interactions. The connections at the rear are eclipsed in this projection. b, Sequence and structure of the B′ BTX tile. Four helical domains, hairpins, are attached perpendicular to the BTX motif, to create a topographic feature that can be detected by AFM. Four lateral and six longitudinal sticky ends are shown in red. Other tiles are shown in Supplementary Information section 1.
Figure 2: DNA seeds. 
a, Seed formation. In step 1, the individual strands of the seed tiles self-assemble in separate vessels to produce seven different BTX tiles, each flanked by unique sticky ends labelled Y and a number; primed numbers are complementary to unprimed numbers. The red tiles are the A tiles and the green tiles are the B tiles. The A tiles contain a biotin group to enable their decoration by streptavidin. The tile labelled A1(I1) is the initiator tile. The strand labelled S on its left can bind to a dynabead during the replication process. In step 2, the tiles are mixed together, producing 7-unit seeds when they are mixed together. In step 3, the tiles are prepared for AFM imaging by the addition of streptavidin. b, AFM images of seeds. The upper left panel shows a typical field of view, of slightly less than 1 μm2. A large number of seeds are present, along with some multimeric complexes. The other three panels are zoomed images. (Black scale bars, 200 nm.) A schematic image of each seed is shown next to the seed.
Figure 3: DNA generations. 
