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- ItemHighly Symmetric and Extremely Compact Multiple Winding Microtubes by a Dry Rolling Mechanism(Weinheim : Wiley-VCH, 2020) Moradi, Somayeh; Naz, Ehsan Saei Ghareh; Li, Guodong; Bandari, Nooshin; Bandari, Vineeth Kumar; Zhu, Feng; Wendrock, Horst; Schmidt, Oliver G.Rolled-up nanotechnology has received significant attention to self-assemble planar nanomembranes into 3D micro and nanotubular architectures. These tubular structures have been well recognized as novel building blocks in a variety of applications ranging from microelectronics and nanophotonics to microbatteries and microrobotics. However, fabrication of multiwinding microtubes with precise control over the winding interfaces, which is crucial for many complex applications, is not easy to achieve by existing materials and technologies. Here, a dry rolling approach is introduced to tackle this challenge and create tight windings in compact and highly symmetric cylindrical microstructures. This technique exploits hydrophobicity of fluorocarbon polymers and the thermal expansion mismatch of polymers and inorganic films upon thermal treatment. Quality parameters for rolled-up microtubes, against which different fabrication technologies can be benchmarked are defined. The technique offers to fabricate long freestanding multiwinding microtubes as well as hierarchical architectures incorporating rolled-up wrinkled nanomembranes. This work presents an important step forward toward the fabrication of more complex but well-controlled microtubes for advanced high-quality device architectures. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
- ItemMechanical Characterization of Compact Rolled-up Microtubes Using In Situ Scanning Electron Microscopy Nanoindentation and Finite Element Analysis(Weinheim : Wiley-VCH, 2021) Moradi, Somayeh; Jöhrmann, Nathanael; Karnaushenko, Dmitriy D.; Zschenderlein, Uwe; Karnaushenko, Daniil; Wunderle, Bernhard; Schmidt, Oliver G.Self-assembled Swiss-roll microstructures (SRMs) are widely explored to build up microelectronic devices such as capacitors, transistors, or inductors as well as sensors and lab-in-a-tube systems. These devices often need to be transferred to a special position on a microchip or printed circuit board for the final application. Such a device transfer is typically conducted by a pick-and-place process exerting enormous mechanical loads onto the 3D components that may cause catastrophic failure of the device. Herein, the mechanical deformation behavior of SRMs using experiments and simulations is investigated. SRMs using in situ scanning electron microscopy (SEM) combined with nanoindentation are characterized. This allows us to mimic and characterize mechanical loads as they occur in a pick-and-place process. The deformation response of SRMs depends on three geometrical factors, i.e., the number of windings, compactness of consecutive windings, and inner diameter of the microtube. Nonlinear finite element analysis (FEA) showing good agreement with experiments is performed. It is believed that the insights into the mechanical loading of 3D self-assembled architectures will lead to novel techniques suitable for a new generation of pick-and-place machines operating at the microscale. © 2021 The Authors. Advanced Engineering Materials published by Wiley-VCH GmbH
- ItemA Novel Large-Scale, Multilayer, and Facilely Aligned Micropatterning Technique Based on Flexible and Reusable SU-8 Shadow Masks(Weinheim : Wiley, 2019) Moradi, Somayeh; Bandari, Nooshin; Bandari, Vineeth Kumar; Zhu, Feng; Schmidt, Oliver G.A simple method to fabricate flexible, mechanically robust, and reusable SU-8 shadow masks is demonstrated. This shadow mask technology has high pattern flexibility as various shapes with different dimensions can be created. The fabricated shadow masks are characterized in terms of the resolution, reusability, and capability of multilayer surface micropatterning. Fabrication of a new plastic photomask for the exposure process simplifies the shadow mask fabrication process and results in higher resolution in the shadow mask structures compared to the commercial chromium photomasks. For the multilayer surface micropatterning technology, a simple and fast alignment technique based on SU-8 pillars and without usage of any microscopic tools is reported. This unique method leads to a less complicated alignment process with the alignment accuracy of ≈2 µm. The proposed shadow mask technology can be easily employed for wafer-scale micropatterning process. The capability of fabricated SU-8 shadow masks in micropatterning on polymer thin films is evaluated by fabricating metallic contacts on poly(3,4-ethylenedioxythiophene) samples and electrical characterization. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim