Inductors are essential components of radio frequency integrated circuits (RFICs). While the active devices in RF systems downscale steadily, inductors have not been able to keep up with the pace of continual miniaturization because of the trade-off between size and performance as well as fabrication complexity. Strain-induced self-rolled-up nanotechnology allows the formation of three-dimensional (3D) architectures, such as multiple-turn spiral tubes, through planar processing. Here, we report on using 3D SiN(x) tubular structures with accompanying prepatterned metal layers, as a novel on-chip tube inductor design platform. We found, by an equivalent lumped circuit and electromagnetic modeling, that the 3D metal spiral structure has the ability to significantly better confine magnetic field compared to conventional planar spiral on-chip inductors. More than 100× reduction in footprint can be realized using this platform while achieving excellent electrical performance, including large inductance, high quality (Q) factor, and high self-resonance frequency (f(0)).

In neural interface platforms, cultures are often carried out on a flat, open, rigid, and opaque substrate, posing challenges to reflecting the native microenvironment of the brain and precise engagement with neurons. Here we present a neuron cell culturing platform that consists of arrays of ordered microtubes (2.7–4.4 μm in diameter), formed by strain-induced self-rolled-up nanomembrane (s-RUM) technology using ultrathin (<40 nm) silicon nitride (SiNx) film on transparent substrates. These microtubes demonstrated robust physical confinement and unprecedented guidance effect toward outgrowth of primary cortical neurons, with a coaxially confined configuration resembling that of myelin sheaths. The dynamic neural growth inside the microtube, evaluated with continuous live-cell imaging, showed a marked increase (20×) of the growth rate inside the microtube compared to regions outside the microtubes. We attribute the dramatic accelerating effect and precise guiding of the microtube array to three-dimensional (3D) adhesion and electrostatic interaction with the SiNx microtubes, respectively. This work has clear implications toward building intelligent synthetic neural circuits by arranging the size, site, and patterns of the microtube array, for potential treatment of neurological disorders.

This study presents the superior structural versatility of strained silicon nitride (SiNx) membranes as a platform for three-dimensional (3D) hierarchical tubular architectures. The effects of compressive and tensile stressed SiNx layer thickness on the self-rolled-up tube curvature, the sacrificial layer etching anisotropy on rolling direction and chirality, and stress engineering by localized thickness control or thermal treatment, are explored systematically. Using strained SiNx membranes as an electrically insulating and optically transparent mechanical support, compact 3D hierarchical architectures involving carbon nanotube arrays and passive electronic components are demonstrated by releasing the functional structures deposited and patterned in 2D. These examples highlight the uniqueness of this platform that exploits 2D processing and self-assembly to achieve highly functional 3D structures.

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Thin‐film, microscale GaAs solar cells transfer printed into luminescent concentrating waveguides show significantly enhanced power output compared to cells evaluated in isolation. Experimental and numerical simulation results demonstrate that optimized configurations involve a free‐standing waveguide and a diffuse backside reflector, as a way to maximize capture of both waveguided and scattered photons. Such unusual options in engineering design suggest promising additional avenues for the use of luminescent concentration in advanced photovoltaics.