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.

Interest in carbon dioxide (CO2) sensors is growing rapidly due to the increasing awareness of the link between air quality and health. Indoor, high CO2 levels signal poor ventilation, and outdoor the burning of fossil fuels and its associated pollution. CO2 gas sensors based on integrated optical waveguides are a promising solution due to their excellent gas sensing selectivity, compact size, and potential for mass manufacturing large volumes at low cost. However, previous demonstrations have not shown adequate performance for atmospheric-level sensing on a scalable platform. Here, we report the clearly resolved detection of 500 ppm CO2 gas at 1 s integration time and an extrapolated 1σ detection limit of 73 ppm at 61 s integration time using an integrated suspended silicon waveguide at a wavelength of 4.2 µm. Our waveguide design enables suspended strip waveguides with bottom anchors while maintaining a constant waveguide core cross-sectional geometry. This unique design results in a low propagation loss of 2.20 dB/cm. The waveguides were implemented in a 150 mm silicon on insulator (SOI) platform using standard optical lithography, providing a clear path to low-cost mass manufacturing. The low CO2 detection limit of our proposed waveguide, combined with its compatibility for high-volume production, creates substantial opportunities for waveguide sensing technology in CO2 sensing applications such as fossil fuel combustion monitoring and indoor air quality monitoring for ventilation and air conditioning systems.

Electrostatically operated micro- and nanoelectromechanical (MEM/NEM) relays have been proposed as digital switches to replace transistors due to their sharp turn-on/off transient, zero leakage current between drain and source in the OFF-state, and capability to operate at far higher temperatures and radiation levels than CMOS. However, the different components associated with energy consumption in MEM/NEM relays, including the dynamic energy associated with charging the gate capacitance and static energy lost through substrate leakage, have not been investigated to date. Here, we present a detailed analysis of the energy consumption of NEM/MEM relays starting from first principles and compare against measurements carried out on silicon MEM relay prototypes. The dynamic energy consumed by a transistor in a binary switching transfer is accurately captured by 0.5CV2. This expression, which has also been used for relays, is only valid under the approximation of an unvarying capacitance C. However, the gate capacitance of an MEM/NEM relay varies as a function of gate voltage, as it is determined by the airgap between the gate electrode and the moving beam. We show how including this effect adds an extra term to the dynamic energy consumption expression. Furthermore, we investigate different current leakage mechanisms and devise a new method to estimate the substrate leakage current based on using the switching hysteresis of relays. The models, analyses, and measurement methodologies presented here constitute a set of essential techniques for accurate estimation of the energy consumption of MEM/NEM relays in ultralow power circuit applications.

Utilizing lanthanide upconversion nanoparticles to convert near-infrared to visible light presents a potential way for fabricating the next generation of low-cost near-infrared imaging sensors. Integrating microlens arrays with upconversion nanoparticles has been shown to be a promising approach for improving the efficiency of upconversion nanoparticles. However, approaches suitable for prototyping and producing microlens arrays to explore optimal device designs are lacking. In this work, we report an approach to fabricating flexible near-infrared-to-visible upconversion devices incorporating upconversion nanoparticles and microlens arrays, which enables easy adjustment of device structures and lens geometry. This is achieved by fabricating flexible films containing upconversion nanoparticles using molding in combination with femtosecond laser 3D printing of lenses, facilitating rapid prototyping for different application scenarios. By adding the microlens array, the intensities of the green (525 and 540 nm) and red (654 nm) upconversion emission bands were enhanced by a factor of 3 and 10, respectively, potentially leading to much reduced detectable near-infrared light intensity.

Single-molecule trapping and analysis are critical in understanding biomolecular processes at an unprecedented resolution. Traditional nanopore systems often face limitations in scalability and integration with electronic components, which complicates their use in compact, high-density applications. Addressing these challenges, we introduce a novel on-chip nanopore array system integrated with a silver (Ag) electrode and self-aligned femtolitersized cavities, representing an innovative approach for electronic single-molecule trapping. Our design utilizes a wafer-scale fabrication process with a buried electrode architecture, enabling the scalable production of high-density nanopore arrays without the need for through-wafer etching. Successful DNA translocation measurements demonstrate the system's potential as a versatile platform for single-molecule trapping and reaction studies.

We will present the advancements in AEOLUS, an H2020 project centered on sensing air quality and numerous gases, developing an integrated and miniaturized solution in Silicon photonics (SiPH). Traditional spectroscopic solutions, while reliable, are often bulky and costly, whereas we follow an integrated photonics solution for robust, miniaturized, and cost-effective systems. The integrated sensors NDIR spectroscopy in the mid-infrared (mid-IR), using suspended waveguide as a sensing element, graphene-based photodetectors for broadband and low power detection. The presented solution leveraged a broadband mid-IR source (thermal) that is cost-efficient and integratable and can greatly expand the applications of photonic integrated circuits (PICs). Thermal incandescent sources are advantageous over other mid-IR emitters based on semiconductor materials in terms of compatibility with PICs, manufacturing costs, and bandwidth. The 2D material used is consistent with the detector, i.e. graphene, a semi-metallic two-dimensional material. The demonstrated graphene mid-IR emitters integrated with photonic waveguides are considered for the mid-IR region relevant to absorption peaks of the gases under investigation for the purposes of air quality. A coupling efficiency of up to 68% is estimated with estimated emitter temperatures up to 1000 °C [1], covering the mid-IR region. The overall concept of AEOLUS also includes a Silicon protective capping lid to safeguard the integrated devices on the chip, assembled at the wafer scale. Results from CO2 and CH4 gas detection using AEOLUS suspended waveguides, at 4.2μm and 3.2μm, respectively, will also be shown (leveraging ideal mid-IR absorption spectral peaks for these gases).

Controlled breakdown has emerged as an effective method for fabricating solid-state nanopores in thin suspended dielectric membranes for various biomolecular sensing applications. On an unpatterned membrane, the site of nanopore formation by controlled breakdown is random. Nanopore formation on a specific site on the membrane has previously been realized using local thinning of the membrane by lithographic processes or laser-assisted photothermal etching under immersion in an aqueous salt solution. However, these approaches require elaborate and expensive cleanroom-based lithography processes or involve intricate procedures using custom-made equipment. Here, we present a rapid cleanroom-free approach using single pulse femtosecond laser exposures of 50 nm thick silicon nitride membranes in air to localize the site of nanopore formation by subsequent controlled breakdown to an area less than 500 nm in diameter on the membrane. The precise positioning of the nanopores on the membrane could be produced both using laser exposure powers which caused significant thinning of the silicon nitride membrane (up to 60% of the original thickness locally), as well as at laser powers which caused no visible modification of the membrane at all. We show that nanopores made using our approach can work as single-molecule sensors by performing dsDNA translocation experiments. Due to the applicability of femtosecond laser processing to a wide range of membrane materials, we expect our approach to simplify the fabrication of localized nanopores by controlled breakdown in a variety of thin film material stacks, thereby enabling more sophisticated nanopore sensors.

Graphene mid-IR photodetectors are a promising choice for on-chip spectroscopy due to their broadband photo-response. However, the low efficiency of coupling light to single-layer graphene hinders the detector responsivity. Here, we demonstrate a plasmon-enhanced graphene-based photothermoelectric detector operating at 4.2 μm wavelength in the mid-infrared. Integrating metallic resonators with the graphene detector tripled its responsivity compared to a pure graphene device, attributed to enhanced graphene-light interaction. Our miniaturized detector is bias-free and has a fast frequency response of 25.6 kHz. Our detector was implemented in a 150 mm silicon-on-insulator (SOI) platform, showing its potential for on-chip integration and high-volume production.

Graphene mid-IR photodetectors are a promisingchoice for on-chip spectroscopy due to their broadbandphoto-response. However, the low efficiency of couplinglight to single-layer graphene hinders the detectorresponsivity. Here, we demonstrate a plasmon-enhancedgraphene-based photothermoelectric detector operating at4.2 μm wavelength in the mid-infrared. Integratingmetallic resonators with the graphene detector tripled itsresponsivity compared to a pure graphene device,attributed to enhanced graphene-light interaction. Ourminiaturized detector is bias-free and has a fast frequencyresponse of 25.6 kHz. Our detector was implemented in a150 mm silicon-on-insulator (SOI) platform, showing itspotential for on-chip integration and high-volumeproduction. 

Solid-state nanopores offer unique possibilities for biomolecule sensing; however, scalable production of sub-5 nm pores with precise diameter control remains a manufacturing challenge. In this work, we developed a scalable method to fabricate sub-5 nm nanopores in silicon (Si) nanomembranes through metal-assisted chemical etching (MACE) using gold nanoparticles. Notably, we present a previously unreported self-limiting effect that enables sub-5 nm nanopore formation from both 10 and 40 nm nanoparticles in the 12 nm thick monocrystalline device layer of a silicon-on-insulator substrate. This effect reveals distinctive etching dynamics in ultrathin Si nanomembranes, enabling precise control over nanopore dimensions. The resulting nanopore sensor, suspended over self-aligned spheroidal oxide undercuts with diameters of just a few hundred nanometers, exhibited low electrical noise and high stability due to encapsulation within dielectric layers. In DNA translocation experiments, our nanopore platform could distinguish folded and unfolded DNA conformations and maintained stable baseline conductance for up to 6 h, demonstrating both sensitivity and robustness. Our scalable nanopore fabrication method is compatible with wafer-level and batch processing and holds promise for advancing biomolecular sensing and analysis.