Controlled Assembly of Semiconducting Polymers: From fundamental understanding towards stretchable electronics

Starting from first-time demonstration of controlled assembly of Poly(3-hexylthiophene) (P3HT), a model conjugated polymer, into mesoscale rod-like features, mechanistic elucidation of mesoscale molecular assembly process of P3HT could be proposed. Application of simple 2-step crystallization model successfully elaborated assembly process of P3HT molecules. We believe that understanding of the conjugated polymer assembly process obtained in this study using P3HT can be expanded to other conjugated molecule-solvent systems so that molecular assembly through solution processing methods can be applied in a more systematic and controllable manner. Further, through systematic interrogation of P3HT films with varied degrees of molecular ordering prepared by controlling assembly of P3HT molecules, an inverse relationship between mechanical resiliency and charge carrier mobility/molecular ordering in conjugated polymer systems was determined definitively. As a solution to the dilemma, a simple elastomer blend approach incorporating the advantages of polymer molecular interactions and crystallization mechanisms was presented. A composite of processed P3HT and Polydimethylsiloxane (PDMS) was shown to create a semiconducting film exhibiting both high ductility and superior mobility versus single component organic semiconductor counterpart.Ph.D

Self-Assembly of Any Shape with Constant Tile Types using High Temperature

Inspired by nature and motivated by a lack of top-down tools for precise nanoscale manufacture, self-assembly is a bottom-up process where simple, unorganized components autonomously combine to form larger more complex structures. Such systems hide rich algorithmic properties - notably, Turing universality - and a self-assembly system can be seen as both the object to be manufactured as well as the machine controlling the manufacturing process. Thus, a benchmark problem in self-assembly is the unique assembly of shapes: to design a set of simple agents which, based on aggregation rules and random movement, self-assemble into a particular shape and nothing else. We use a popular model of self-assembly, the 2-handed or hierarchical tile assembly model, and allow the existence of repulsive forces, which is a well-studied variant. The technique utilizes a finely-tuned temperature (the minimum required affinity required for aggregation of separate complexes). We show that calibrating the temperature and the strength of the aggregation between the tiles, one can encode the shape to be assembled without increasing the number of distinct tile types. Precisely, we show one tile set for which the following holds: for any finite connected shape S, there exists a setting of binding strengths between tiles and a temperature under which the system uniquely assembles S at some scale factor. Our tile system only uses one repulsive glue type and the system is growth-only (it produces no unstable assemblies). The best previous unique shape assembly results in tile assembly models use O(K(S)/(log K(S))) distinct tile types, where K(S) is the Kolmogorov (descriptional) complexity of the shape S

Covert Computation in Self-Assembled Circuits

Traditionally, computation within self-assembly models is hard to conceal because the self-assembly process generates a crystalline assembly whose computational history is inherently part of the structure itself. With no way to remove information from the computation, this computational model offers a unique problem: how can computational input and computation be hidden while still computing and reporting the final output? Designing such systems is inherently motivated by privacy concerns in biomedical computing and applications in cryptography. In this paper we propose the problem of performing "covert computation" within tile self-assembly that seeks to design self-assembly systems that "conceal" both the input and computational history of performed computations. We achieve these results within the growth-only restricted abstract tile assembly model (aTAM) with positive and negative interactions. We show that general-case covert computation is possible by implementing a set of basic covert logic gates capable of simulating any circuit (functionally complete). To further motivate the study of covert computation, we apply our new framework to resolve an outstanding complexity question; we use our covert circuitry to show that the unique assembly verification problem within the growth-only aTAM with negative interactions is coNP-complete

Self-Replication via Tile Self-Assembly (Extended Abstract)

In this paper we present a model containing modifications to the Signal-passing Tile Assembly Model (STAM), a tile-based self-assembly model whose tiles are capable of activating and deactivating glues based on the binding of other glues. These modifications consist of an extension to 3D, the ability of tiles to form "flexible" bonds that allow bound tiles to rotate relative to each other, and allowing tiles of multiple shapes within the same system. We call this new model the STAM*, and we present a series of constructions within it that are capable of self-replicating behavior. Namely, the input seed assemblies to our STAM* systems can encode either "genomes" specifying the instructions for building a target shape, or can be copies of the target shape with instructions built in. A universal tile set exists for any target shape (at scale factor 2), and from a genome assembly creates infinite copies of the genome as well as the target shape. An input target structure, on the other hand, can be "deconstructed" by the universal tile set to form a genome encoding it, which will then replicate and also initiate the growth of copies of assemblies of the target shape. Since the lengths of the genomes for these constructions are proportional to the number of points in the target shape, we also present a replicator which utilizes hierarchical self-assembly to greatly reduce the size of the genomes required. The main goals of this work are to examine minimal requirements of self-assembling systems capable of self-replicating behavior, with the aim of better understanding self-replication in nature as well as understanding the complexity of mimicking it

Algorithmic Assembly of Nanoscale Structures

The development of nanotechnology has become one of the most significant endeavors of our time. A natural objective of this field is discovering how to engineer nanoscale structures. Limitations of current top-down techniques inspire investigation into bottom-up approaches to reach this objective. A fundamental precondition for a bottom-up approach is the ability to control the behavior of nanoscale particles. Many abstract representations have been developed to model systems of particles and to research methods for controlling their behavior. This thesis develops theories on two such approaches for building complex structures: the self-assembly of simple particles, and the use of simple robot swarms. The concepts for these two approaches are straightforward. Self-assembly is the process by which simple particles, following the rules of some behavior-governing system, naturally coalesce into a more complex form. The other method of bottom-up assembly involves controlling nanoscale particles through explicit directions and assembling them into a desired form. Regarding the self-assembly of nanoscale structures, we present two construction methods in a variant of a popular theoretical model known as the 2-Handed Tile Self-Assembly Model. The first technique achieves shape construction at only a constant scale factor, while the second result uses only a constant number of unique particle types. Regarding the use of robot swarms for construction, we first develop a novel technique for reconfiguring a swarm of globally-controlled robots into a desired shape even when the robots can only move maximally in a commanded direction. We then expand on this work by formally defining an entire hierarchy of shapes which can be built in this manner and we provide a technique for doing so

Developments of Advanced Cathodes and Stabilized Zinc Anodes for High-performance Aqueous Zinc-ion Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) have attracted considerable attention as one of the most promising energy storage systems for the grid-scale application owing to the natural merits of metallic Zn, including a high theoretical capacity, suitable redox potential, low cost, high safety, and eco-friendliness. However, the existing aqueous ZIBs are far from satisfying the requirements of practical applications. Significant challenges hindering the further development of ZIBs come from the low utilization and poor cycling stability of cathodes and limited reversibility of Zn anodes associated with dendrite growth, corrosion, and passivation. To date, enormous efforts have been devoted to developing high-performance cathode materials, reliable electrolytes, and stable Zn anodes to achieve ZIB with high energy and power densities and long cycle life. These progresses have been reviewed in this dissertation. Regarding the main issues of ZIBs, the dissertation covered both the cathode and anode to comprehensively improve the electrochemical performance of ZIBs. For the cathode, high-performance manganese oxide-based cathode materials have been developed by in-situ electrochemical activation of MnS, and rational design of hierarchical core-shell MnO2@carbon nanofiber structures. To further understand the underlying reasons for the enhanced electrochemical performance, the charge storage mechanisms of manganese oxide-based cathodes in ZIBs have been in-depth investigated. With respect to the Zn anode, a thin polyvinyl alcohol (PVA) coating layer on the Zn anode has enabled dendrite-free, long-life aqueous Zn batteries by effectively regulating the interfacial ion diffusion and inducing the homogeneous Zn nucleation and deposition of stacked plates with preferentially crystallographic orientation along (002)Zn planes. This work is expected to provide facile and low-cost approaches for developing high-performance, cost-effective, and stable aqueous ZIBs and shed light on a new mechanistic understanding of manganese oxide-based cathodes

Design Rules for Obtaining Narrow Luminescence from Semiconductors Made in Solution

Solution-processed semiconductors are in demand for presentandnext-generation optoelectronic technologies ranging from displaysto quantum light sources because of their scalability and ease ofintegration into devices with diverse form factors. One of the centralrequirements for semiconductors used in these applications is a narrowphotoluminescence (PL) line width. Narrow emission line widths areneeded to ensure both color and single-photon purity, raising thequestion of what design rules are needed to obtain narrow emissionfrom semiconductors made in solution. In this review, we first examinethe requirements for colloidal emitters for a variety of applicationsincluding light-emitting diodes, photodetectors, lasers, and quantuminformation science. Next, we will delve into the sources of spectralbroadening, including "homogeneous" broadening fromdynamical broadening mechanisms in single-particle spectra, heterogeneousbroadening from static structural differences in ensemble spectra,and spectral diffusion. Then, we compare the current state of theart in terms of emission line width for a variety of colloidal materialsincluding II-VI quantum dots (QDs) and nanoplatelets, III-VQDs, alloyed QDs, metal-halide perovskites including nanocrystalsand 2D structures, doped nanocrystals, and, finally, as a point ofcomparison, organic molecules. We end with some conclusions and connections,including an outline of promising paths forward