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 demonstrate a dither-locking scheme that stabilizes an integrated silicon photonic ring-resonator add-drop filter to an external laser wavelength using an electrostatic MEMS phase tuner. We achieve a millisecond-scale step response, highlighting MEMS actuation as a route to low-power stabilization.

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.

Silicon photonics is accelerating high-performance computing, and integrated MEMS devices offer low-power reconfiguration. However, MEMS device performance is limited by lithography resolution. Here, we unveil a post-fabrication technique to reduce a photonic foundry-defined 230 nm starting gap to 50 nm, using a nonvolatile MEMS switch.

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.

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.

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.

We demonstrated a suspended germanium-onsilicon waveguide for long-wave infrared sensing. An 1 1 μ m deepetched air gap eliminates silicon substrate losses, achieving a low propagation loss of 2.4 ~dB / cm at 9.2 μ ~m. We reported, to the best of our knowledge, the first on-chip detection of ethanol gas.

3D printing at the macroscale has evolved from making plastic prototypes to the production of high-performance functional metal parts for industries such as medical and aerospace. By contrast, MEMS devices today are produced in large quantities using semiconductor manufacturing processes. However, the semiconductor manufacturing paradigm is not cost-effective for producing customized MEMS devices in small to medium volumes (tens to thousands of units per year), and related applications are difficult to address efficiently. 3D printing of functional MEMS devices could play an important role in filling this gap. Here, we discuss recent advances in 3D- printed functional MEMS, addressing the challenges of economical customization at smaller production volumes.

We present a fabrication process for 3D printing of glass sensors directly onto the end of optical fiber tips. Compared to conventional polymeric 3D-printed fiber-tip sensors, our method provides far superior chemical resistance and mechanical durability. We demonstrate the utility of our sensors by reliably measuring the refractive index of aggressive organic solvents - environments where polymer-based sensors are prone to swelling and deformation. This breakthrough opens new avenues for deploying robust glass sensors in demanding industrial settings, such as chemical processing plants and oil refineries, where precise and durable refractive index measurements are essential.