Recent development of portable and wearable electronics inspires diverse application potentials in health care, communications, and aerospace. Meanwhile, the growing need for fast data processing in wearable electronics also challenges the material and device design for efficient energy generation, storage and consumptions. Using non-Si nano-materials in future electronics/optoelectronics is expected to promote data processing speed while dramatically lower energy consumption by 1 or 2 magnitudes. However, even though energy-efficient prototypical devices are demonstrated with non-Si materials, they still suffer from low manufacturing resolution/precision, limited manufacturing scalability, and simple architectures complexity. As results, non-Si devices still cannot compete with existing Si devices.
I envision that the missing link bridging current synthetic foundation for functional nano-materials to the emerging challenges in energy-efficient 3D electronic/optoelectronic is a cross-scale patterning technique that precisely positions functional non-Si nano-materials into programmable 3D architectures at both high spatial resolution (sub-10 nm) and lithographic precision (sub-5 nm). Such assembled architectures should be designed de novo and fabricated in a scalable fashion to direct heterogeneous nano-materials with high spatial positioning resolution and balance the competing needs from high device performance and low energy consumption.
I believe that recent development of bio-molecular self-assembly, in particular DNA self-assembly, will promise an innovative strategy to potentially address this emerging challenge, through interfacing with functional materials. Based on my previous experiences in programming DNA self-assembly and DNA-directed material fabrication for electronics and plasmonics, I propose to develop a scalable framework using DNA brick crystals as templates for cross-scale positioning of functional nano-materials, such as carbon nanotubes and nanoparticles, into energy-efficient 3D electronic/optoelectronic devices at 2-nm spatial positioning resolution. Micron-scale mono-dispersed 3D DNA brick crystals will be firstly designed and assembled from millions heterogeneous building blocks at 2-nm spatial resolution, following de novo developed growth pathway. Next, spatially confined chemical recognitions between DNA brick crystal templates and selected non-Si nano-materials direct the high-precision positioning of nano-entities exclusively at pre-designed positions with desired orientations, forming arbitrary prescribed 3D architectures tailored to device architecture at lithographic precision. Cross-scale integration of the micron-scale architectures into millimeter scale, in collaboration with soft lithography (imprint lithography and contact printing) and dry etching, constructs the designed energy-efficient 3D electronic/optoelectronic devices from novel non-Si materials, with resolution and precision beyond the scope of existing photolithography and block-copolymer lithography.
Towards this framework, I will lead the transformative researches addressing several scientific and technical challenges, and demonstrate the innovative 3D electronic/optoelectronic products with unique energy-efficient features. Scientifically, I will explore the crystallization principles for complex self-assembly systems with highly distinct local interactions and diverse conflict growth pathways dominated by entropy and enthalpy effects. Technically, I will develop spatial-confined chemical patterning at single-molecule resolution, which simplifies orientation control during scaling nano-entities and enables lithographic precision (down to 1 nm) for complex nano-entities within prescribed irregular architectures. High-precision reproducible pattern transfer from DNA brick crystal template to functional relevant substrates expands the device dimension from individual micron array to millimeter scale integrated circuit, and finalizes the scalable production of target device with 10 to 100 times lower energy consumption than Si analogues.
The general theme of my postdoctoral research focuses on using self-assembled DNA nanostructures for digital fabrication and assembly of inorganic nano-materials, such as metals, carbon, and Si, under solution synthesis and lithographic conditions. By transferring geometrical information from the DNA templates into inorganic nano-materials, nano-materials with complex prescribed shapes can be rationally designed and reliably fabricated at high spatial resolution. To expand the DNA self-assembly into micron scale architectures, we also develop a new framework, DNA brick crystal, which is a 2D DNA film with complex prescribed 3D morphologies assembled from modular DNA bricks at 2-nm spatial resolution. Using these DNA brick crystals as structural templates for scaling up nano-materials into larger prescribed architectures, we further demonstrate the periodicity scaling of carbon nanotubes arrays and Si trench arrays down to 10-12 nm ranges, beyond the scope of existing photolithography and block copolymer lithography.
Specifically, my postdoc work includes: (1) DNA nano-foundry. We have developed the synthetic foundation towards a digital fabrication framework using DNA nanostructure as templates: Casting to confine 3D metal nanoparticle growth using DNA mold (Science 2014); Etching to use metallized DNA nanostructure as lithographic masks for graphene patterning (Nature Commun. 2013); Welding to fuse nanoparticles patterned on DNA template into continuous metal nanostructure, and Coating to grow conformal inorganic oxides on DNA substrates (J. Am. Chem. Soc. 2013). This synthetic foundation enables us to design a complex 2D/3D inorganic shape de novo and fabricate it with high-resolution. (2) DNA brick crystal with prescribed depths. Using DNA bricks, we invented a simple, robust and general approach to engineer complex micron scale two-dimensional crystals (lattice structures with repetitive structural units) with prescribed depths of up to 80 nm (Nature Chem. 2014). These self-assembled DNA brick crystals exhibit sophisticated user-specified nanometer-scale three-dimensional features, including intricate cavities, channels, and tunnels. During crystal growth, assembly and disassembly occur via relatively weak intermolecular interactions involving the addition or subtraction of a single short strand at a time. (3) Scaling-up with DNA brick crystals. Self-assembled micron scale DNA brick crystals provide new platforms for scaling-up the integration of nano-materials into larger in silico designed architectures. For example, metal nanoparticles can be selectively docked onto DNA brick crystals to form the prescribed 2D and 3D nanoparticle arrays with precise inter-particle spacing control. These DNA brick crystals could also be used as lithographic masks to create parallel Si lines on substrate with 10-12-nm periodicity or for spatially confining carbon nanotubes with programmable periodicity from 24 nm to 8 nm at lithographic precision.
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