RESUMEN

Multimaterial mechanisms are seen throughout natural organisms across all length scales. The different materials in their bodies, from rigid, structural materials to soft, elastic materials, enable mobility in complex environments. As robots leave the lab and begin to move in real environments, including a range of materials in 3D robotics mechanisms can help robots handle uncertainty and lessen control requirements. For the smallest robots, soft materials combined with rigid materials can facilitate large motions in compact spaces due to the increased compliance. However, integrating various material components in 3D at the microscale is a challenge. We present an approach for 3D microscale multimaterial fabrication using two-photon polymerization. Two materials with three orders of magnitude difference in Young's moduli are printed in consecutive cycles. Integrating a soft elastic material that is capable of more than 200% strain along with a rigid material has enabled the formation of hybrid elements, strongly adhered together, with layer accuracy below 3-µm resolution. We demonstrate a multilink multimaterial mechanism showing large deformation, and a 3D-printed 2-mm wingspan flapping wing mechanism, showing rapid prototyping of complex designs. This fabrication strategy can be extended to other materials, thus enhancing the functionality and complexity of small-scale robots.

RESUMEN

Additive manufacturing processes enable fabrication of complex and functional three-dimensional (3D) objects ranging from engine parts to artificial organs. Photopolymerization, which is the most versatile technology enabling such processes through 3D printing, utilizes photoinitiators that break into radicals upon light absorption. We report on a new family of photoinitiators for 3D printing based on hybrid semiconductor-metal nanoparticles. Unlike conventional photoinitiators that are consumed upon irradiation, these particles form radicals through a photocatalytic process. Light absorption by the semiconductor nanorod is followed by charge separation and electron transfer to the metal tip, enabling redox reactions to form radicals in aerobic conditions. In particular, we demonstrate their use in 3D printing in water, where they simultaneously form hydroxyl radicals for the polymerization and consume dissolved oxygen that is a known inhibitor. We also demonstrate their potential for two-photon polymerization due to their giant two-photon absorption cross section.

RESUMEN

Inorganic nanocrystals are attractive materials for solar-cell applications. However, the performance of such devices is often limited by an insufficient alignment of energy levels in the nanocrystals. Here, we report that by attaching two different molecules to a single quantum dot or nanocrystal one can induce electric fields large enough to significantly alter the electronic and optoelectronic properties of the quantum dot. This electric field is created within the nanocrystals owing to a mixture of amine- and thiol-anchor-group ligands. Examining the steady state as well as temporal evolution of the optical properties and the nuclear magnetic resonances of the nanocrystals we found that the first excitonic peak shifts as a function of the capping-layer composition. We also demonstrate that the use of a mixed-ligand-induced electric field markedly enhances the charge generation efficiency in layer-by-layer CdSe-nanocrystal-based solar cells, thus improving the overall cell efficiency.

RESUMEN

We demonstrate tuning of the electronic level positions with respect to the vacuum level in colloidal InAs nanocrystals using surface ligand exchange. Electrochemical as well as scanning tunneling spectroscopy measurements reveal that the tuning is largely dependent on the nanocrystal size and the surface linking group, while the polarity of the ligand molecules has a lesser effect. The implications of affecting the electronic system of nanocrystal through its capping are illustrated through prototype devices.

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RESUMEN

The main advantage of autonomous biomolecular computing devices over electronic computers is their ability to interact directly with biological systems. No interface is required since all components of molecular computers, including hardware, software, input, and output are molecules that interact in solution along a cascade of programmable chemical events. Here, we demonstrate for the first time that the output of a computation preduced by a molecular finite automaton can be a visible bacterial phenotype. Our 2-symbol-2-state finite automaton utilized linear double-stranded DNA inputs that were prepared by inserting a string of six base pair symbols into the lacZ gene on the pUC18 plasmid. The computation resulted in a circular plasmid that differed from the original pUC18 by either a 9 base pair (accepting state) or 11 base pair insert (unaccepting state) within the lacZ alpha region gene. Upon transformation and expression of the resultant plasmids in E. coli, the accepting state was represented by production of functional beta-galactosidase and formation of blue colonies on X-gal medium. In contrast, the unaccepting state was represented by white colonies due to a shift in the open reading frame of lacZ.

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