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He, Xiaojin

Publications and source records attributed to He, Xiaojin.

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Litters of self-replicating origami cross-tiles

Significance In nature, self-replication and exponential growth are common. Here we introduce a system of artificial self-replicators based on DNA origami cross-tile motifs. Unlike previous systems based on making a single copy of a parent template, the cross-tile systems, like many natural species, can produce “litters” of offspring per generation. The cross-tiles enable a ladder-like structure to crystallize from the template on cooling. UV exposure covalently binds the assembled components of the offspring and heating releases the autonomous daughters from the parent, up to 10 offspring per cycle. The enhanced growth rate speeds up experimental studies and provides an evolutionary advantage for selection.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Multivalent, multiflavored droplets by design

Nature self-assembles functional materials by programming flexible linear arrangements of molecules and then folding them to make 2D and 3D objects. To understand and emulate this process, we have made emulsion droplets with specific recognition and controlled valence. Uniquely monovalent droplets form dimers: divalent lead to polymer-like chains, trivalent allow for branching, and programmed mixtures of different valences enable a variety of designed architectures and the ability to subsequently close and open structures. Our functional building blocks are a hybrid of micrometer-scale emulsion droplets and nanoscale DNA origami technologies. Functional DNA origami rafts are first added to droplets and then herded into a patch using specifically designated “shepherding” rafts. Additional patches with the same or different specificities can be formed on the same droplet, programming multiflavored, multivalence droplets. The mobile patch can bind to a patch on another droplet containing complementary functional rafts, leading to primary structure formation. Further binding of nonneighbor droplets can produce secondary structures, a third step in hierarchical self-assembly. The use of mobile patches rather than uniform DNA coverage has the advantage of valence control at the expense of slow kinetics. Droplets with controlled flavors and valences enable a host of different material and device architectures.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2017

Sequential self-assembly of DNA functionalized droplets

Complex structures and devices, both natural and manmade, are often constructed sequentially. From crystallization to embryogenesis, a nucleus or seed is formed and built upon. Sequential assembly allows for initiation, signaling, and logical programming, which are necessary for making enclosed, hierarchical structures. Though biology relies on such schemes, they have not been available in materials science. We demonstrate programmed sequential self-assembly of DNA functionalized emulsions. The droplets are initially inert because the grafted DNA strands are pre-hybridized in pairs. Active strands on initiator droplets then displace one of the paired strands and thus release its complement, which in turn activates the next droplet in the sequence, akin to living polymerization. This strategy provides time and logic control during the self-assembly process, and offers a new perspective on the synthesis of materials.

36 MATERIALS SCIENCE↗