Resolving the underlying mechanisms of complex brain functions and associated disorders remains a major challenge in neuroscience, largely due to the difficulty in mapping large-scale neural network dynamics with high spatiotemporal resolution. Multimodal neural platforms that integrate optical and electrical modalities offer a promising approach that surpasses resolution limits. Over the last decade, transparent graphene microelectrodes have been proposed as highly suitable multimodal neural interfaces. However, their fabrication commonly relies on the manual transfer process of pre-grown graphene sheets which introduces reliability and scalability issues. In this study, multilayer graphene microelectrode arrays (MEAs) with electrode sizes as small as 10–50 µm in diameter, are fabricated using a transfer-free process on a transparent substrate for in vitro multimodal platforms. For the first time, the capability of transparent graphene electrodes with a diameter of just 10 µm to reliably capture extracellular spiking activity with high signal-to-noise ratios (up to ∼25 dB) is demonstrated. The recorded signal quality is found to be more limited by the electrode-tissue coupling than the MEA technology itself. Overall, this study shows the potential of transfer-free multilayer graphene MEAs to interface with neural tissue, paving the way to advancing neuroscientific research through the next-generation of multimodal neural interfaces.

Studying the polarization and spectral distortion of the Cosmic Microwave Background (CMB) in tandem with intensity fluctuations of the Cosmic Infrared Background (CIB) allows us to verify our assumptions on cosmic inflation and investigate the dynamics and evolution of galaxy clusters in the last 10 billion years. Because of its broadband emission and being an all-sky extended source, observing the entire CMB in detail is a very time-consuming and expensive exercise. Fortunately, in the last few years, the on-chip superconducting spectrometer technology has moved out of the lab and into the telescope. With its compact size and background-limited sensitivity, this family of instruments is particularly well-suited for fast and large area observations in a relatively unexplored range of the electromagnetic spectrum. However, recent examples of this technology do not yet reach the requirements needed for large spectroscopic and polarimetric surveys of the CMB. We formulate several of these requirements and introduce novel on-chip components and fabrication techniques. We introduce a cross-over to enable distinguishing signal polarization, minimize signal loss by locally optimized lithography of a coplanar-waveguide (CPW), lower the spectral resolution of microstrip filters by deposition of a dielectric layer, and increase the yield of the spectrometer array by removing individual line shorts. These together have culminated in the successful fabrication of a fourteen-spaxel IFU.

Two-dimensional (2D) graphene holds enormous potential as a future candidate for gas sensors, not only coming from its vast surface area, but also contributed by the highly active edges, which have promptly become a research hotspot. In this work, we developed a novel transfer-free approach to prepare chemical vapor deposited (CVD) edge-exposed multilayer graphene micromeshes by pre-patterning the molybdenum (Mo) catalyst through photolithography. Our facile and efficient approach provides fewer steps, higher accuracy, and virtually unrestricted patternable features. It is also semiconductor manufacturing compatible with precise alignment and positioning for wafer-scale mass production. Graphene micromeshes with different thicknesses were prepared and studied for NO₂ (∼1 ppm) gas sensing. Despite the reduction in the surface area, the micromeshes still delivered an enhancement of the overall response (for 20 min CVD graphene, from 0.692% to 0.744%). Based on our proposed calculation model, which hypothetically separates the response from the surface and edges, thinner multilayer graphene edges exhibited exceptionally high sensitivity compared to the surface due to higher reactivity and edge-facilitated gas adsorption. Our pre-patterning method and study of graphene micromesh-based prototype gas sensors provide insights into the role of the edges of multilayer graphene, which could potentially be a vital part for future high-performance gas sensors.

The unique properties of two-dimensional (2D) materials bring great promise to improve sensor performance and realise novel sensing principles. However, to enable their high-volume production, wafer-scale processes that allow integration with electronic readout circuits need to be developed. In this perspective, we review recent progress in on-chip 2D material sensors, and compare their performance to the state-of-the-art, with a focus on results achieved in the Graphene Flagship programme. We discuss transfer-based and transfer-free production flows and routes for complementary metal-oxide-semiconductor integration and prototype development. Finally, we give an outlook on the future of 2D material sensors, and sketch a roadmap towards realising their industrial and societal impact.

Low-loss deposited dielectrics are beneficial for the advancement of superconducting integrated circuits for astronomy. In the microwave band (approximately 1-10 GHz) the dielectric loss at cryogenic temperatures and low electric field strengths is dominated by two-level systems. However, the origin of the loss in the millimeter-submillimeter band (approximately 0.1-1 THz) is not understood. We measured the loss of hydrogenated-amorphous-SiC films in the 0.27-100-THz range using superconducting-microstrip resonators and Fourier-transform spectroscopy. The agreement between the loss data and a Maxwell-Helmholtz-Drude dispersion model suggests that vibrational modes above 10 THz dominate the loss in hydrogenated amorphous SiC above 200 GHz.

In this work, we demonstrate the use of a micro-hotplate (MHP) with graphene integrated without transfer step for NO₂ sensing. The MHP can rapidly recover the device to its initial conditions by applying a brief heat pulse. Moreover, by employing a process without graphene transfer, we prevent random polymer contamination from the transfer process. The (up to 8) graphene sensors on a single MHP show a very similar response. Finally, we demonstrate that we can extract the relative humidity from the device's response immediately after the MHP is turned off in a humid environment.

Depending on the applications based on graphene, single-layer or few-layer graphene would be more beneficial. Ideally, graphene could be nucleated directly with the required thickness. However, some aspects related to graphene thickness and uniformity control still need to be solved. This work aims to better understand graphene formation using Mo thin films as a catalyst. The grown graphene films were characterized using SEM, TEM, XPS, AFM, standard Raman spectroscopy and 3D Raman surface imaging. A correlation between the catalyst thickness and the number of layers is established. All the characterization techniques show that the number of graphene layers inversely scales with the Mo catalyst thickness used for the graphene synthesis. Then, by simply adjusting the catalyst thickness, the number of graphene layers can be engineered from few-layer graphene (FLG) up to multi-layer graphene (MLG). A pinhole distribution of 1 % was detected on the films synthesized on 50 nm and 100 nm Mo thicknesses after the catalyst was etched. On the synthesized FLG (500 nm Mo), no holes were observed on the surface film after the etching process and even after a transfer onto another substrate. These results can enable the formation of FLG with a controlled thickness and good uniformity.

In this work, we report a simple, scalable, and dry fabrication technique for realizing thin-film platinum resistance temperature detectors (RTDs), utilizing spark ablation technology. Pure spark-ablated platinum nanoparticles, with an average diameter of around 2.2 nm, were directly deposited through chemical-free impaction printing onto the substrate, enabling direct sensor patterning without complex processing steps. Experimental investigations revealed that higher deposition speeds produce sparser and thermally unstable films, with 1 mm/min identified as the optimal printing rate. Additionally, it was established that the film temperature coefficient of resistance (TCR) improves with increasing layer thickness, achieving a maximum mean TCR of 2.17 × 10−3°C−1 for an 8-layer RTD. The printed Pt sensor demonstrated linear temperature-resistance characteristics while maintaining high stability and repeatability over multiple thermal cycles, spanning 25–200 °C. This study lays the groundwork for advancing practical and cost-effective printed thermal sensing technologies.

The term graphene-based gas sensors may be too broad, as there are many physicochemical differences within the graphene-based materials (GBM) used for chemiresistive gas sensors. These differences condition the sensitivity, selectivity, recovery, and ultimately the sensing performance of these devices towards air pollutants. Continuous ultraviolet irradiation aids in the desorption of gas molecules and enhances sensor performance. Under these conditions, the devices from this work can reliably monitor NO₂ and CO at room temperature, below the human-recommended exposure limits, presenting NO₂ LoD down to ∼20 ppb. By selecting GBMs with different levels of defectivity, which influence gas adsorption dynamics, and through comprehensive characterization, including D, D′, D″, 2D, and G Raman bands, graphene-based gas sensors can be tailored to meet specific sensing requirements. This study examines five different non-oxidized GBM to develop tools and gain a deeper understanding of the relationships between GBM properties and their sensing performance. This research introduces a new standard for defect assessment, moving beyond graphene's D and G Raman band intensity ratio, to facilitate the successful integration of graphene-based gas sensors into everyday applications, such as environmental monitoring and industrial safety, and potentially impacting other 2D materials, thereby reducing health risks associated with air pollution.

In this study, we investigated the effect of vertically aligned carbon nanofiber (VACNF) density on ethanol vapor sensing performance. VACNFs were synthesized on Si substrates using plasma-enhanced chemical vapor deposition (PECVD), where varying the acetylene flow rate resulted in different fiber densities. Morphological characterization confirmed that higher acetylene flow leads to improved alignment and denser CNF networks. Raman spectroscopy revealed reduced defect levels and increased graphitization with increasing density. Gas sensing measurements showed that moderate to high CNF densities significantly enhance sensor conductivity and ethanol sensitivity due to improved charge transport paths and increased active surface area. These results highlight the importance of CNF density optimization in designing high-performance gas sensors.

Since the performance of micro-electro-mechanical system (MEMS)-based microphones is approaching fundamental physical, design, and material limits, it has become challenging to improve them. Several works have demonstrated graphene’s suitability as a microphone diaphragm. The potential for achieving smaller, more sensitive, and scalable on-chip MEMS microphones is yet to be determined. To address large graphene sizes, graphene-polymer heterostructures have been proposed, but they compromise performance due to added polymer mass and stiffness. This work demonstrates the first wafer-scale integrated MEMS condenser microphones with diameters of 2R = 220–320 μm, thickness of 7 nm multi-layer graphene, that is suspended over a back-plate with a residual gap of 5 μm. The microphones are manufactured with MEMS compatible wafer-scale technologies without any transfer steps or polymer layers that are more prone to contaminate and wrinkle the graphene. Different designs, all electrically integrated are fabricated and characterized allowing us to study the effects of the introduction of a back-plate for capacitive read-out. The devices show high mechanical compliances C_m = 0.081–1.07 μmPa⁻¹ (10–100 × higher than the silicon reported in the state-of-the-art diaphragms) and pull-in voltages in the range of 2–9.5 V. In addition, to validate the proof of concept, we have electrically characterized the graphene microphone when subjected to sound actuation. An estimated sensitivity of S_1kHz = 24.3–321 mV Pa⁻¹ for a V_bias = 1.5 V was determined, which is 1.9–25.5 × higher than of state-of-the-art microphone devices while having a ~9 × smaller area. (Figure presented.).

As a consequence of their high strength, small thickness, and high flexibility, ultrathin graphene membranes show great potential for pressure and sound sensing applications. This study investigates the performance of multi-layer graphene membranes for microphone applications in the presence of air-loading. Since microphones need a flatband response over the full audible bandwidth, they require a sufficiently high mechanical resonance frequency. Reducing membrane thickness facilitates meeting this bandwidth requirement, and therefore, also allows increasing compliance and sensitivity of the membranes. However, at atmospheric pressure, air-loading effects can increase the effective mass, and thus, reduce the bandwidth of graphene and other 2D material-based microphones. To assess the severity of this performance-limiting effect, we characterize the acoustic response of multi-layer graphene membranes with a thickness of 8 nm in the pressure range from 30 to 1000 mbar, in air and helium environments. A bandwidth reduction by a factor ∼ 2.8 × for membranes with a diameter of 500 μm is observed. These measurements show that air-loading effects, which are usually negligible in conventional microphones, can lead to a substantial bandwidth reduction in ultrathin graphene microphones. With analytical and finite element models, we further analyze the performance limits of graphene microphones in the presence of air-loading effects.

Synchronized rectifiers offer promising solutions for piezoelectric energy harvesting; however, achieving the promised energy extraction performance necessitates using either a bulky inductor or multiple large capacitors, which cannot be on-chip integrated and increase the system form factor. This article introduces a fully integrated sequenced synchronized switch harvesting on capacitors (3SHC) rectifier. The input piezoelectric transducer (PT) uses microelectromechanical system technology. The cantilever is equally split into multiple strongly coupled subcantilevers, with each cantilever treated as an individual PT connected to the proposed rectifier. The 3SHC rectifier cyclically operates multiple times to synchronously flip the voltage of each cantilever sequentially. With the proposed design, all the flying capacitors only need to match the capacitance of each subcantilever; hence, they can be fully integrated on-chip. The design is fabricated using standard 0.18 μ m CMOS technology. Measurement results show that the proposed 3SHC rectifier attains an 80% voltage flip efficiency and achieves a 730% power enhancement compared to a full-bridge rectifier.

The authors regret that in the above article the Fig. 3 contains an error of cross-section image of group C at 48 h on Page 4. Fig. 3 should read: This correction does not influence the method, results and conclusions of the original article. The authors would like to apologise for any inconvenience caused.

Silicon carbide (SiC) coated vertically aligned carbon nanotubes (VACNT) are attractive material for fabricating MEMS devices as an alternative for bulk micromachining of SiC. In order to examine the mechanical properties of SiC-CNT composites at high temperatures, we fabricated VACNT micro-pillars with different amounts of SiC coating and performed high-temperature micro-pillar compression on these samples. The indentation result shows that the coating can improve the elastic modulus up to three orders of magnitude. Samples were tested at room temperature, 300°C, 600°C, and 900°C under compressive load. No significant degradation of the mechanical properties was observed at elevated temperatures, demonstrating the harsh environment potential of this composite.

In this paper, we present the surface modification of multilayer graphene electrodes with platinum (Pt) nanoparticles (NPs) using spark ablation. This method yields an individually selective local printing of NPs on an electrode surface at room temperature in a dry process. NP printing is performed as a post-process step to enhance the electrochemical characteristics of graphene electrodes. The NP-printed electrode shows significant improvements in impedance, charge storage capacity (CSC), and charge injection capacity (CIC), versus the equivalent electrodes without NPs. Specifically, electrodes with 40% NP surface density demonstrate 4.5 times lower impedance, 15 times higher CSC, and 4 times better CIC. Electrochemical stability, assessed via continuous cyclic voltammetry (CV) and voltage transient (VT) tests, indicated minimal deviations from the initial performance, while mechanical stability, assessed via ultrasonic vibration, is also improved after the NP printing. Importantly, NP surface densities up to 40% maintain the electrode optical transparency required for compatibility with optical imaging and optogenetics. These results demonstrate selective NP deposition and local modification of electrochemical properties in graphene electrodes for the first time, enabling the cohabitation of graphene electrodes with different electrochemical and optical characteristics on the same substrate for neural interfacing.

Integrated circuits based on wide bandgap semiconductors are considered an attractive option for meeting the demand for high-temperature electronics. Here, we report an analog-to-digital converter fabricated in a silicon carbide complementary metal-oxide-semiconductor technology now available through Europractice. The MOSFET component in this technology was measured up to 500 °C, and the key parameters, such as threshold voltage, field-effect mobility, and channel-length modulation parameters, were extracted. A 4-bit flash data converter, consisting of 266 transistors, is implemented with this technology and demonstrates correct operation up to 400 °C. Finally, the gate oxide quality is investigated by time-dependent dielectric breakdown measurements at 500 °C. A field-acceleration factor of 4.4 dec/(MV/cm) is obtained by applying the E model.

The demand for accurate temperature sensing in extreme temperatures is increasing. Traditional silicon-based integrated temperature sensors usually cannot survive above 200 °C. Many researchers have started to focus on semiconductors with a large bandgap. Among them, silicon carbide (SiC) is the most promising one. Nevertheless, most reported SiC sensors are in the form of discrete components and are not compatible with integrated electronics. In this work, we demonstrate an open 4H-SiC CMOS technology, and the fabrication steps are detailed. The temperature sensing elements in this technology, including resistors based on different implanted layers and MOSFETs, are characterized up to 600 °C. At room temperature, the resistive-based elements demonstrate large negative temperature coefficients of resistance (TCRs). With increasing temperature, the TCR starts to decrease and even becomes positive. The TCR change is due to the interplay between increasing dopant ionization rate and decreasing mobility as a function of temperature. The resistance change with temperature fits well into the Steinhart-Hart model and second-order polynomial equation. The p-type diode-connected MOSFET has a sensitivity of 4.35 mV/°C with a good linearity. The nMOS-based sensor has a maximum sensitivity of -9.24 mV/°C but a compromised linearity. The characterization of these sensing elements provides important results for potential users who will work on SiC integrated temperature sensing with this technology.

Due to the deficient passivation of the interface between silicon carbide and silicon dioxide, the defect-induced capture and release of trapped charges triggered by external Bias Temperature Stress (BTS) leads to parameter shifts and degraded device performance. This study models the trap-induced transient current in silicon carbide metal-oxide-semiconductor capacitors, providing insight into how capacitance and conductance change during C-V measurements under conditions of high temperature, varied frequency, and varied applied voltage.

The continuing drive to miniaturise electronic devices requires an understanding of how the materials in these devices behave under stress, particularly with respect to electromigration. In this study, we explore the relationship between the microstructure of copper (Cu) and electromigration by using an approach that combines in situ Scanning Electron Microscopy (SEM) with Electron Backscatter Diffraction (EBSD). This in-situ SEM-EBSD technique enables real-time observation and analysis of electromigration-induced microstructure changes. Our investigation provides detailed insights into the microstructure effect on electromigration. Specifically, samples annealed at 300 °C showed void formation after the electromigration test and higher Kernal average misorientation (KAM) values, indicating higher internal strains and an inhomogeneous microstructure. In contrast, samples annealed at 500 °C maintained lower KAM values with minimal changes in crystal orientation, highlighting a more stable and uniform electromigration-resistant microstructure. Our results demonstrate the critical role of microstructure in determining the electromigration resistance of copper interconnects. By optimizing the annealing temperature, the reliability of the copper microstructure can be significantly improved by reducing the dislocations and increasing grain size, thus extending its lifetime.