Browsing by Subject "Nanowire assembly"

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Rational fabrication, assembling and actuation of nanowire multi-mer nanomotors
(2015-08) Hong, Ki-Pyo, M.S. in Engineering; Fan, Donglei; Li, Wei
Direct field induced manipulations of nanowires have been recognized as a possible alternative to conventional chemical based assembling techniques. In particular, manipulation of nanowires with an external electric field allows the facile and precision assembly of nanowires into various nanoscale devices. In this study, we have rationally synthesized multisegment Au/Ni nanowires and assembled them into a unique type of rotary nanomotors made of nanowire multi-mers with designed geometric configurations by the electric tweezers. The electric tweezers are a recent invention developed by Prof. Fan’s group, which are based on the combined electrophoretic and dielectrophoretic forces to transport and align nanowires independently in low Reynolds number suspensions. The Au/Ni multi-segmented nanowires are rationally designed and fabricated by electrodeposition into nanoporous templates. By employing the ferromagnetic properties of the nickel segments in the nanowires, we precisely transported and assembled randomly disperse nanowires into multi-mer nanowire devices with designed configuration and further assembled them as the rotors of nanomotors. The magnetic attraction between the Ni segments in the nanowires holds the joints of dimers, trimers and tetramers tightly. The rotary nanomotors made of multiple assembled nanowires with designed configuration are the first to the best of our knowledge. Our study of their rotation behaviors as functions of voltage and frequency shows that the rotational speed of the nanomotors linearly increases with the square of the applied AC voltages and depends on the AC frequencies. The voltage square dependence is highly desirable for achieving ultrahigh speed rotation. This research could generate interest and impact multiple research fields including nanoelectromechanical system (NEMS) devices, nanomotors, microfluidic architectures and single-cell biology.
Solution-processible nanomaterials for flexible electronic production
(2022-08-10) Liu, Wen (Ph. D. in chemical engineering); Korgel, Brian Allan, 1969-; Milliron, Delia; Truskett, Thomas; Yu, Guihua
Flexible solar cells emerge as the need for clean energy resources arises in many complex scenarios, demanding device tolerance with irregular geometries. Bendable or even foldable devices with atypical form factors fit for a wide range of applications, such as integration with building designs, smart home “Internet-of-Things” systems, wearable electronics. Implementation of nanomaterials into flexible devices, owing to their solution processible and flexible nature, can further lower production costs while improving device flexibility; tunable properties of nanomaterials can also add in versatility of device functions. Ultrathin CuInSe₂ nanocrystal solar cells with a total thickness less than 20 μm, are enabled by both nanomaterial incorporation and photonic lift-off technique. Photonic lift-off provides ultrafast, clean, and high-throughput processing, to separate flexible devices from the underlying rigid support. CuInSe₂ nanocrystal solar cells can be produced in flexible format through the photonic lift-off process, after the device flexibility was greatly improved by the replacement of indium tin oxide in the top contact with spray-coated silver nanowires. In contrast to nanowire assembly produced from spray coating with a disordered morphology, regular assembly of nanowires which exhibits a higher level of uniformity, could lead to enhancement of the intrinsic nanowire properties. A simple toluene-water system, utilizing the interface formed between the two immiscible liquids, is able to drive nanowires to align side by side into monolayers, creating centimeter-wide coverage. Uniformity in nanowire alignment across hundreds of microns gives rise to anisotropic properties such as birefringence, revealing their potential to be used as building blocks of optoelectronics. Last but not the least, near-infrared active plasmonic CuInSe₂ nanocrystals were achieved through cation exchange. A post-synthetic heat treatment of CuInSe₂ nanocrystals with Cd²⁺ sources induced plasmon-enhanced absorption around 0.85 eV. Cd incorporation generates free carriers and expands the pristine chalcopyrite crystal lattice, as a result of the introduced substitutional and interstitial defects. These studies provided deep insights into the structure and properties of solution-processible nanomaterials, to advance their applications for flexible electronic production.