Among topological solitons, magnetic skyrmions are two-dimensional particle-like objects with a continuous winding of the magnetization, and magnetic Hopfions are three-dimensional objects that can be formed from a closed loop of twisted skyrmion strings. Theoretical models suggest that magnetic Hopfions can be stabilized in frustrated or chiral magnetic systems, and target skymions can be transformed into Hopfions by adapting their perpendicular magnetic anisotropy, but their experimental verification has been elusive so far. Here, we present an experimental study of magnetic Hopfions that are created in Ir/Co/Pt multilayers shaped into nanoscale disks, known to host target skyrmions. To characterize three-dimensional spin textures that distinguish Hopfions from target skyrmions magnetic images are recorded with surface-sensitive X-ray photoemission electron microscopy and bulk-sensitive soft X-ray transmission microscopy using element-specific X-ray magnetic circular dichroism effects as magnetic contrast. These results could stimulate further investigations of Hopfions and their potential application in three-dimensional spintronics devices.

Modern metamaterials face functional constraints as they are commonly embedded in or deposited on dielectric materials. We provide a new solution by microfabricating a completely free-standing all-metal self-supported metamaterial. Using upright S-string architecture with the distinctive feature of metallic transverse interconnects, we form a locally stiff, globally flexible space-grid. Infrared Fourier transform interferometry reveals the typical double-peak structure of a magnetically excited left-handed and an electrically excited right-handed pass-band that is maintained under strong bending and heating, and is sensitive to dielectrics. Exploiting UV/X-ray lithography and ultimately plastic moulding, meta-foils can be mass manufactured cost-effectively to serve as optical elements.

Benzocyclobutene (BCB) is a thermosetting polymer that can form microfluidics and bond top and bottom layers of the microfluidics at the same time, and yields high repeatability and high bonding strength. This paper reports using photosensitive BCB to fabricate microfluidics and to bond with a thermal press for 4 in. wafers. By optimizing the parameters for pattern development and using a three-stage temperature and pressure increment BCB bonding, we realize the whole wafer glassSi or glass-glass bonding in thermal press without any crack. The wafer-level bonding shows a bonding percentage above 70%, a tensile stress above 4.94 MPa, and a bonding repeatability over 95%. Furthermore, the bonding is compatible with thick electrode integration, that microfluidics with 380 nm thick electrodes underneath can be well-bonded. Our bonding method much reduces the cost compared with bonding BCB in a wafer bonding machine.

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This paper investigates in detail the profiles of the nanostructures fabricated by nanosphere lithography through oblique deposition and perpendicular etching. 2D or 3D nanostructures can be achieved by this cost-effective method. Because the optical response of a particular nanoparticle depends on its size and shape, this angle deposition method can produce various shapes of nanostructures, which are suitable for localized surface plasmon resonance biosensor applications. The nanostructure profiles under various deposition and etching conditions are simulated in our work. The calculated 3D profiles are verified by the 3D nanostructures fabricated in our experiments, and the calculated 2D profiles are in good agreement with the fabricated nanocrescents reported by another research group. This paper gives a full theoretical solution of the obtainable nanostructure shapes by nanosphere lithography utilizing oblique deposition and perpendicular etching.