Soheil Daryadel

Multi-physics simulation of metal printing at micro/nanoscale using meniscus-confined electrodeposition: Effect of environmental humidity

Capability to print metals at micro/nanoscale in arbitrary 3D patterns at local points of interest will have applications in nano-electronics and sensors. Meniscus-confined electrodeposition (MCED) is a manufacturing process that enables depositing metals from an electrolyte containing nozzle (pipette) in arbitrary 3D patterns. In this process, a meniscus (liquid bridge or capillary) between the pipette tip and the substrate governs the localized electrodeposition process. Fabrication of metallic microstructures using this process is a multi-physics process in which electrodeposition, fluid dynamics, and mass and heat transfer physics are simultaneously involved. We utilized multi-physics finite element simulation, guided by experimental data, to understand the effect of water evaporation from the liquid meniscus at the tip of the nozzle for deposition of free-standing copper microwires in MCED process.

Multi-physics simulation of metal printing at micro/nanoscale using meniscus-confined electrodeposition: Effect of nozzle speed and diameter

Meniscus-confined electrodeposition (MCED) is a solution-based, room temperature process for 3D printing of metals at micro/nanoscale. In this process, a meniscus (liquid bridge or capillary) between a nozzle and a substrate governs the localized electrodeposition process, which involves multiple physics of electrodeposition, fluid dynamics, mass, and heat transfer. We have developed a multiphysics finite element (FE) model to investigate the effects of nozzle speed ( v N ) and nozzle diameter (D0) in the MCED process. The simulation results are validated with experimental data. Based on theoretical approach and experimental observation, the diameter of the deposited wire is in the range of 0.5–0.9 times of the nozzle diameter. The applicable range for vN for various nozzle diameters is computed. The results showed that the contribution of migration flux to total flux remains nearly constant (∼50%) for all values of pipette diameter in the range examined (100 nm–5 μm), whereas the contribution of diffusio...

Microscale 3D Printing of Nanotwinned Copper

Nanotwinned (nt)-metals exhibit superior mechanical and electrical properties compared to their coarse-grained and nanograined counterparts. nt-metals in film and bulk forms are obtained using physical and chemical processes including pulsed electrodeposition (PED), plastic deformation, recrystallization, phase transformation, and sputter deposition. However, currently, there is no process for 3D printing (additive manufacturing) of nt-metals. Microscale 3D printing of nt-Cu is demonstrated with high density of coherent twin boundaries using a new room temperature process based on localized PED (L-PED). The 3D printed nt-Cu is fully dense, with low to none impurities, and low microstructural defects, and without obvious interface between printed layers, which overall result in good mechanical and electrical properties, without any postprocessing steps. The L-PED process enables direct 3D printing of layer-by-layer and complex 3D microscale nt-Cu structures, which may find applications for fabrication of metamaterials, sensors, plasmonics, and micro/nanoelectromechanical systems.

Localized Pulsed Electrodeposition Process for Three-Dimensional Printing of Nanotwinned Metallic Nanostructures

Nanotwinned-metals (nt-metals) offer superior mechanical (high ductility and strength) and electrical (low electromigration) properties compared to their nanocrystalline (nc) counterparts. These properties are advantageous in particular for applications in nanoscale devices. However, fabrication of nt-metals has been limited to films (two-dimensional) or template-based (one-dimensional) geometries, using various chemical and physical processes. In this Letter, we demonstrate the ambient environment localized pulsed electrodeposition process for direct printing of three-dimensional (3D) freestanding nanotwinned-Copper (nt-Cu) nanostructures. 3D nt-Cu structures were additively manufactured using pulsed electrodeposition at the tip of an electrolyte-containing nozzle. Focused ion beam (FIB) and transmission electron microscopy (TEM) analysis revealed that the printed metal was fully dense, and was mostly devoid of impurities and microstructural defects. FIB and TEM images also revealed nanocrystalline-nanotwinned-microstructure (nc-nt-microstructure), and confirmed the formation of coherent twin boundaries in the 3D-printed Cu. Mechanical properties of the 3D-printed nc-nt-Cu were characterized by direct printing (FIB-less) of micropillars for in situ SEM microcompression experiments. The 3D-printed nc-nt-Cu exhibited a flow stress of over 960 MPa, among the highest ever reported, which is remarkable for a 3D-printed material. The microstructure and mechanical properties of the nc-nt-Cu were compared to those of nc-Cu printed using the same process under direct current (DC) voltage.

Nano-precision micromachined frequency output profilometer

This work presents a new class of MEMS based frequency output force and displacement probes with sub-nm displacement resolution. The sensor consists of a probe tip attached to a microcantilever coupled to a thermal-piezoresisitve resonator. Application of a displacement to this probe tip causes deflection of the cantilever due to the applied force. Consequently, the force acting on the cantilever is transferred to the piezoresisitve beam, modulating its stiffness and thus the resonance frequency. Such devices can be used as atomic force microscope (AFM) probes or high resolution surface profilometers with fully electrical operation eliminating the bulky and complex optical detectors typically used in such systems. As a proof-of-concept, such a microcantilever coupled to a 2.1MHz thermal-piezoresisitve resonator has been demonstrated with a displacement sensitivity of 1.5Hz/nm. The Allan deviation for such resonators operated as self-sustained oscillators is measured to be 0.1–0.2ppm. On analysis of the measured data, a frequency resolution in the order of 1Hz is expected to be achievable. This, in turn, translates to ∼0.4nm of displacement and ∼11nN of force resolution for such sensors.