Nanoelectromechanical (NEM) switches have near vertical turn-off transient, zero off-state leakage, and non-volatile behavior, ideal qualities for low power computing and memory applications. To realize this potential, large-scale integration of NEM switches is required. Here we introduce a three-dimensional (3-D) heterogeneous integration platform that leverages a standard silicon-on-insulator (SOI) CMOS foundry process, combined with post-processing of the foundry wafers to integrate silicon NEM switches. Within this platform, we seamlessly integrated both volatile 3-terminal (3-T) and nonvolatile 7-terminal (7-T) NEM switches. We demonstrate successful electrical programming and reprogramming of both switch types, validating the platform’s functionality and its potential for constructing densely integrated NEM switch-based logic circuits and non-volatile memories.

We developed a transfer bonding method for large-scale integration of MEMS devices directly on standard CMOS foundry wafers, enabling novel applications of sophisticated, programmable MEMS circuits. Further, we developed a hermetic sealing process, also based on wafer-level transfer bonding, to protect the MEMS devices.

Ice lithography (IL) is an emerging and versatile direct write method that complements two photon lithography and focused electron beam induced deposition (FEBID). Based on interaction between energetic electrons and frozen materials, IL permits the creation of high-resolution 2D patterns and intricate 3D micro- and nanostructures. This review highlights advancements spanning the past five years. Several notable breakthroughs have been reported during this time frame including the development of i) new classes of low-toxicity IL materials, including organometallics and renewable materials such as CO2 and ethanol; ii) innovative new substrates such as biological materials and even living micro-organisms; iii) disruptive processes, hardware and digital methods to obtain complex 3D objects; and iv) cutting-edge applications in 2D materials research, direct synthesis of quantum dots for sensing, and ultra-high density data storage. These discoveries offer the opportunity to focus on exciting future applications, and this review peeks into the future through a roadmap on how recent progress in IL might enable innovations into apparent unrelated fields of cancer screening, fundamental biophysics, quantum technology, future microsensor production, and more generally advanced functional materials research.

Micro- and nanoscale patterning of conformal thin-film coatings on the exterior surfaces of complex three-dimensional (3D) structures is essential for emerging applications such as soft robotics, photonics, and functional 3D-printed MEMS devices. However, existing methods struggle to deliver high-resolution patterning on complex 3D structures and often suffer from poor thickness control, and inadequate surface conformity of the thin-film coatings. Here we present a robust approach for patterning of conformal thin-film coatings on complex 3D structures, including on sloped surfaces with angles up to 90°, with multiscale dimensions from 100 μm to 100 nm, and even down to the sub-30 nm scale when mask shrinkage techniques are used. This patterning approach utilizes a lithographically defined 3D Scaffold-Architected Lift-Off (SALO) mask in the lift-off process. It is agnostic to the used thin-film deposition process and enables even lift-off patterning of atomic layer deposited (ALD) conformal coatings, a task infeasible for conventional shadowing-based lift-off processes. Our approach opens opportunities for manufacturing complex 3D structures at the micro- and nanoscale by enabling lithographic patterning on the exterior surfaces of arbitrary 3D structures.

Nanoelectromechanical (NEM) switches are promising for ultra-low-power electronics in harsh environments due to their zero leakage current and radiation hardness. However, their mechanical robustness under extreme loads remains insufficiently studied. This work investigates the performance of 3-terminal and 7-terminal NEM relays subjected to mechanical shocks up to 5000 g and vibrations up to 70 g. All tested devices retained mechanical functionality, confirming excellent structural integrity. Electrical characterisation revealed variations in pull-in and pull-out voltages and loss of programmed states in 7T relays, although their non-volatile capability remained intact. These instabilities are primarily attributed to the soft Au contact coating, which is prone to wear and deformation. The findings highlight the suitability of NEM technology for harsh environments and point to future improvements through more suitable contact materials and device miniaturization.

Nanoelectromechanical (NEM) relays have emerged as a compelling alternative to solid-state switches for digital logic and power gating due to their near-zero off-state leakage and abrupt turn on/off characteristics. Here, we demonstrate a novel application of a dual-beam, 4-terminal NEM relay to function as a direct voltage comparator for Pulse-Width-Modulation (PWM) encoding in Voltage-to-Time converter (VTC) applications. A prototype device with an actuation airgap of 400nm was fabricated on a silicon-on-insulator substrate and the switch contact features were coated with ruthenium to improve the cycling lifetime. The pull-in and pull-out voltages of the relay were measured to be 13.21 V and 10.22 V, respectively. In subsequent experiments the relay successfully converted a slow sinusoidal signal into a duty-cycle-modulated output. Although the input frequency was deliberately kept low to accommodate reliability issues in the prototype, this work serves as a proof-of-concept to showcase the potential of using our 4-T NEM relay as a building block in VTC applications at the edge of the network.

Integrated optical microsystems are key to next-generation communication, sensing, and quantum technologies, with the potential to exceed the capabilities of conventional microelectronics. Such systems rely on precise control of light, but creating optimal 3D micro-optics is challenging for conventional microfabrication technologies. Multiphoton lithography (MPL) offers nanoscale 3D printing capabilities, while efforts to extend MPL to high-performance glasses typically involve harsh high-temperature or chemical postprocessing that is incompatible with integrated optical microsystems. To address this, we explore the use of hydrogen silsesquioxane (HSQ), an inorganic precursor, for MPL. We demonstrate postprocessing-free 3D printing of solid silica glass and self-forming glass nanogratings with nanoscale resolution. These advances enable the direct integration of glass micro-optics on photonic chips and optical fibers. We present functional 3D-printed glass optical devices, including on-chip ring resonators and photoluminescent sources, and fiber-tip refractive index sensors and polarization beam splitters, opening new avenues for high-performance optical microsystem integration.

Solid-state nanopores in ultrathin (<20 nm) membranes enable label-free single-molecule sensing, but their adoption as sensors is limited by the lack of scalable manufacturing methods that deliver nanopores with single-nanometer reproducibility. Self-limiting metal-assisted chemical etching (MACE) in silicon-on-insulator (SOI) membranes offers a parallel wet-chemical route for nanopore fabrication, yet prior demonstrations lacked a predictive design rule and required electron microscopy or electrical tests for confirming presence and number of pores. Here, we convert self-limiting MACE into a manufacturing-oriented workflow with optical process control to obtain and verify the formation of 4 nm nanopores in a scalable fashion. We decouple the deposition of 200 +/- 10 nm gold (Au) nanoparticles from etching, enabling independent optimization of the two steps. The nanoparticle size allows for particle-per-membrane counting by dark-field optical microscopy, so that deposition can be repeated when counts are below target. We then map etching behavior across Au nanoparticle diameter d (10-200 nm) and silicon (Si) device-layer thickness t (5-18 nm), finding that d/t >= 0.8 ratio predicts self-limiting MACE behavior, where pore diameter becomes independent of particle size. In this regime, 200 +/- 10 nm catalysts yield 4 +/- 1 nm pores, corresponding to a reduction of similar to 50 & times; in pore diameter and similar to 10 & times; in pore-diameter variability compared to the catalyst diameter and related variability. Successful through-membrane pore formation produces undercuts in the buried oxide (typically similar to 200-300 nm diameter) beneath each pore, which can be characterized for each membrane by bright-field microscopy and used as a proxy for the otherwise optically invisible 4 nm pores. Together, the predictive d/t framework and two-stage optical verification establish a scalable wet-chemical route to fabricate nanopores for biomolecular sensing and related nanofluidic devices.

Nanopores in ultrathin membranes are central to single-molecule sensing, filtration, and energy conversion applications, yet fabrication of solid-state nanopores remains limited by fundamental trade-off between resolution, throughput, and tool complexity. Here, we report a scalable nanopore fabrication process that exploits stress-induced mechanical ripping to detach a fragment from a membrane with lateral dimensions in the nm-scale, forming pores with diameters down to the sub-10 nm regime, which is well below the resolution limit of the employed lithography. Using this approach, we demonstrate wafer-scale fabrication of nanopores at densities exceeding 105 pores per cm2 in dielectric (HfO2), semiconducting (SiGe), and metallic (Cr) membranes, including suspended HfO2 membranes as thin as 2 nm. We demonstrate the utility of the fabricated nanopores for high-performance surface enhanced Raman readouts of single molecule translocations. Beyond nanopore fabrication, this fracture-based approach points to broader opportunities for nanometer- and atomic-scale structuring of ultrathin materials.

Germanium-based integrated photonics is gaining attention due to its potential for mid-infrared wavelength applications, including environmental sensing, industrial gas monitoring, defense, and security. However, current germanium-on-silicon platforms face significant propagation losses at wavelengths above 8 μm, and gas sensing in this regime using a germanium waveguide has not been demonstrated to date. To address this challenge, we introduce a suspended germanium-on-silicon platform, where an 11 μm deep suspension gap ensures optical mode isolation from the lossy silicon substrate. The waveguide has a low propagation loss of 3.5 dB/cm at a wavelength of 9.2 μm. Furthermore, we demonstrate on-chip ethanol gas sensing in the long-wave infrared range with a detection limit of 925 ppm using this platform. Our method paves the way for extending the operating wavelength range of germanium-on-silicon integrated photonics into the long-wave infrared.