On-chip Sensor Research Articles

Dual-parameter cell biosensor for real-time monitoring of effects of propionic acid on neurons.

Currently, only a few small devices are capable of continuously recording the physiological states of neurons in real time. Micro-electrode arrays (MEAs) are widely used as electrophysiological technology to detect the excitability of neurons non-invasively. However, the development of miniaturized and multi-parameter MEAs capable of real-time recording remains challenging. In this study, an on-chip micro-electrode and platinum resistor array (MEPRA) biosensor was designed and fabricated to monitor both the electrical and temperature signals of cells synchronously in real time. Such on-chip sensor maintains high sensitivity and stability. The MEPRA biosensor was further used to investigate the effects of propionic acid (PA) on primary neurons. The results demonstrate that PA affects the temperature and firing frequency of primary cortical neurons in concentration-dependent manners. The changes of temperature and firing frequency work in tandem with neuronal physiological status, including neuron viability, intracellular calcium concentration, neural plasticity, and mitochondrial function. This highly biocompatible, stable, and sensitive MEPRA biosensor may provide high-precision reference information for investigating the physiological responses of neuron cells under various conditions.

Semi-Passive RFID Electronic Devices With On-Chip Sensor Fusion Capabilities for Motion Capture and Biomechanical Analysis

This paper presents the development and testing of a novel electronic device for Wireless Motion Capture (W-MoCap), a technology that allows the reconstruction of movements of objects and body parts with many potential applications in various contexts. The device integrates UHF RFID technology with sensors for low-power backscattering communication. It consists of a Battery Assisted Passive UHF RFID chip, an Inertial Measurement Unit, an ultra-low power microcontroller, and a custom-designed edge-fed body-tolerant antenna operating at 866 MHz. The proper matching between the RFID chip and antenna is ensured through a well-designed L-match unbalanced network, and the separation of RF and DC signals is achieved with a meandered microstrip quarter-wavelength transformer, choke inductor, and decoupling capacitor. The designed and realized RFID W-MoCap Sensor-Tag has been thoroughly evaluated in terms of current consumption, front-end sensitivity, and sensing accuracy. Finally, five prototypes have been applied to specific segments of a human subject and successfully tested in a practical scenario for real time reconstruction of human movements.

Temperature compensation of MEMS resonant accelerometers with an on-chip platinum film thermometer

Temperature-dominated drift is generally the main error source for high-performance micromachined resonant accelerometers (MRAs) due to inherent thermal stress effect of resonator structure and die-attach process. This paper describes the design and experimental evaluation of a temperature compensation scheme for MEMS resonant accelerometers that demonstrates excellent bias and scale factor stability against temperature variation. An on-chip temperature sensor fabricated by sputtering platinum film on glass substrate is proposed to accurately sense the temperature-induced frequency change of the resonator. A polynomial fitting-based post-compensation model is firstly used to suppress the temperature sensitivity of the MRA over dynamic temperature environment. The temperature drift test and compensation of four accelerometer prototypes in a range from −40 ∘C to 60 ∘C show that the stability of bias and scale factor has been improved greatly with navigation-grade performance. Temperature compensation results with three improved drift models based on polynomial fitting, convolutional neural network and support vector regression respectively are presented and compared to suppress the temperature drift hysteresis in consecutive temperature-varying tests. These experimental results indicate that this resonant accelerometer exhibits excellent temperature stability after compensation, which offers the promise for high-performance inertial navigation applications.

A Differential THz/MW Sensor for Characterizing Liquid Samples Based on CSRs

A differential on-chip sensor loaded with circular spiral resonators (CSRs) for charactering liquid samples is proposed in this manuscript. The proposed on-chip sensor is working at Terahertz (THz) frequency band, and the sensor can be fabricated by integrated passive device (IPD) technology. With comparison to square and octagonal spiral resonators, the circular spiral resonator (CSR) has a higher quality factor and a stronger confinement of electrical field, which are beneficial to improve the measurement sensitivity. The proposed sensor has a differential structure, and two circular spiral resonators are equally distributed on both sides of the microstrip line, and one resonator is regarded as reference, another is utilized as test. The frequency shift and notched magnitude of transmission coefficient will be changed by loading liquid samples with different complex permittivity, thus, the relevant mathematical relationship between S-parameters and permittivity can be established. However, as the cost of fabricating on-chip sensor by IPD technology is nearly half million of RMB, so printed circuit board (PCB) technology is used to fabricate the proposed sensor and to verify the feasibility of the sensor. It should be noted that the on-chip sensor operates at THz band, while the PCB-based sensor operates at MW band. The experiment shows that the proposed CSRs-based MW sensor has a high sensitivity of about 0.28 %. When the real permittivity changes by one unit, the resonant frequency shifts for the microwave sensor and THz sensor are about 0.445 GHz and 1.45 GHz, i.e., 0.445 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GHz</i> /εʹ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>r</i></sub> and 1.45 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">GHz</i> /εʹ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>r</i></sub> , respectively. Obviously, the on-chip THz sensor has a higher resolution than the microwave sensor. All in all, the proposed differential microwave CSR-based sensor is a good candidate in the field of microfluidic measurement.

On-Chip Self-Sensing Piezoelectric Micro-Lens Actuator With Feedback Control

High-speed micro-lens actuators are required for fast auto-focusing in miniaturized cameras. The speed can be enhanced by adding damping at the resonance frequency through feedback control. Previous approaches to implement the feedback control were based on expensive off-chip bulky laser sensors that are not suitable for miniaturized cameras. In this paper, using an on-chip self-sensing piezoelectric sensor with a novel readout circuit, a passive resonant controller is designed, implemented, and tested. The stability of the closed-loop micro-lens actuator is guaranteed through the use of mixed negative-imaginary and passivity theory in the controller design. The performance of the controller with the on-chip self-sensing piezoelectric sensor and readout circuit is compared to that off-chip laser sensor, and results show comparable performance. The closed-loop micro-lens actuator with the on-chip piezoelectric sensor damps the fundamental resonance mode by 20.6 dB, which is similar to the 21.9 dB reduction obtained using the off-chip laser sensor. The settling time for the closed-loop actuator using the on-chip self-sensing piezoelectric sensor is less than 10 ms, which is also comparable to the 8 ms obtained with the off-chip laser sensor. The signal-to-noise ratios for the on-chip self-sensing piezoelectric sensor and off-chip laser sensor are 108 dB and 118 dB, respectively. These results show that the piezoelectric micro-lens actuator using the on-chip self-sensing piezoelectric sensor can replace the bulky and expensive off-chip laser sensor without sacrificing performance, making it more appealing for portable micro-optics devices.

Rabi splitting and unidirectional reflectionless propagation in one-dimensional topological plasmonic crystal

In this paper, we study the strong coupling between the topological edge state and Fabry–Perot cavity state in a one-dimensional plasmonic crystal heterostructure. Finite element method simulations show that a significant plasmonic Rabi splitting is achieved in the near-infrared region and Rabi energy can reach up to 45.5 meV. A dual-band near-perfect absorption phenomenon can be observed, and a coupled oscillator model is proposed to explain the origin of Rabi splitting. In addition, the dual-band unidirectional reflectionless plasmonic propagation in the Rabi splitting region is investigated, and the non-Hermitian scattering matrix is used to verify the existence of double exceptional points. The study may find applications in plasmonic switchers, on-chip sensors, diode-like devices, and filters.

Broadband transverse unidirectional scattering and large range nanoscale displacement measuring based on the interaction between a tightly focused azimuthally polarized beam and a silicon hollow nanostructure.

We theoretically propose a broadband transverse unidirectional scattering scheme based on the interaction between a tightly focused azimuthally polarized beam (APB) and a silicon hollow nanostructure. When the nanostructure is located at a specific position in the focal plane of the APB, the transverse scattering fields can be decomposed into contributions from transverse components of the electric dipoles, longitudinal components of magnetic dipoles and magnetic quadrupole components. In order to satisfy the transverse Kerker conditions for these multipoles within a wide infrared spectrum, we design a novel nanostructure with hollow parallelepiped shape. Through numerical simulations and theoretical calculations, this scheme exhibits efficient transverse unidirectional scattering effects in the wavelength range of 1440 nm to 1820 nm (380 nm). In addition, by adjusting the position of the nanostructure on the x-axis, efficient nanoscale displacement sensing with large measuring ranges can be achieved. After analyses, the results prove that our research may have potential applications in the field of high-precision on-chip displacement sensors.

Optical properties of chiral three-dimensional photonic crystals

We perform a theoretical and numerical study of the optical properties of both direct and inverse three-dimensional (3D) chiral woodpile structures and a corresponding chiral Bragg stack, also known as a Reusch pile. We compute transmission spectra in the helical direction for finite crystals and photonic band structures, where we ensure the effective index of all structures to be the same. We find that both 3D structures show dual-band circular dichroism, where light with a particular circular polarization state---either left- or right-handed---reveals a broad stop band with major attenuation, whereas the other polarization state is transmitted nearly unimpeded. We observe such gaps in different frequency ranges with alternating handedness. The appearance of the circular-polarized gaps is successfully interpreted with a physical model wherein the circular polarization either corotates or counterrotates with the chiral structure, thereby effectively leading to a spatially dependent or a constant refractive index, and thus to the presence or absence of a gap. We find that the presence or absence of circularly polarized gaps is tuned by the transverse periods perpendicular to the chiral axis in both the 3D direct and inverse chiral woodpile crystal structures. The tunability of circular dichroism may find applications as on-chip sensors for circularly polarized light and in the on-chip detection of chiral molecules.

On-Chip Integrated High-Sensitivity Temperature Sensor Based on p-GaN/AlGaN/GaN Heterostructure

An on-chip integrated temperature sensor based on a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN/AlGaN/GaN heterostructure is demonstrated. The sensor consists of a two-dimensional-electron-gas (2DEG) resistor and a Schottky-metal/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</i> -GaN/AlGaN/GaN (PiN) diode, which are connected in series and fabricated on one heterostructure. The conduction current of the 2DEG resistor features a negative temperature-dependence, while that in the PiN diode features a positive dependence due to its bipolar-electron/hole-injection nature. When they are properly biased, the divided voltage between the two units is redistributed with elevated temperatures. At a supply voltage of 10 V, the sensor presents a maximum and recorded sensitivity of 19.7 mV/°C in a temperature range from 25 °C to 300 °C due to the opposing temperature dependence of the two units. The fabrication process and the heterostructure of the temperature sensor are fully compatible with high-electron-mobility transistors, enabling <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">in situ</i> temperature detection and protection with enhanced accuracy and sensitivity.

Automatic optimization of miniaturized bound states in the continuum cavity.

Bound states in the continuum (BICs) provide, what we believe to be, a novel and efficient way for light trapping. However, using BICs to confine the light into a three-dimensional compact volume remains a challenging task, since the energy leakage at the lateral boundaries dominates the cavity loss when its footprint shrinks to considerably small, and hence, sophisticated boundary designs turn out to be inevitable. Conventional design methods fail in solving the lateral boundary problem because a large number of degree-of-freedoms (DOFs) are involved. Here, we propose a fully automatic optimization method to promote the performance of lateral confinement for a miniaturized BIC cavity. Briefly, we combine a random parameter adjustment process with a convolutional neural network (CNN), to automatically predict the optimal boundary design in the parameter space that contains a number of DOFs. As a result, the quality factor that is accounted for lateral leakage increases from 4.32 × 104 in the baseline design to 6.32 × 105 in the optimized design. This work confirms the effectiveness of using CNNs for photonic optimization and will motivate the development of compact optical cavities for on-chip lasers, OLEDs, and sensor arrays.

Titanium Nitride Plasmonic Nanohole Arrays for CMOS-Compatible Integrated Refractive Index Sensing: Influence of Layer Thickness on Optical Properties

The combination of nanohole arrays with photodetectors can be a strategy for the large-scale fabrication of miniaturized and cost-effective refractive index sensors on the Si platform. However, complementary metal–oxide–semiconductor (CMOS) fabrication processes place restrictions in particular on the material that can be used for the fabrication of the structures. Here, we focus on using the CMOS compatible transition metal nitride Titanium Nitride (TiN) for the fabrication of nanohole arrays (NHAs). We investigate the optical properties of TiN NHAs with different TiN thicknesses (50 nm, 100 nm, and 150 nm) fabricated using high-precision industrial processes for possible applications in integrated, plasmonic refractive index sensors. Reflectance measurements show pronounced Fano-shaped resonances, with resonance wavelengths between 950 and 1200 nm, that can be attributed to extraordinary optical transmission (EOT) through the NHAs. Using the measured material permittivity as an input, the measured spectra are reproduced by simulations with a large degree of accuracy: Simulated and measured resonance wavelengths deviate by less than 10 nm, with an average deviation of 4 nm observed at incidence angles of 30° and 40°. Our experimental results demonstrate that an increase in the thickness of the TiN layer from 50 to 150 nm leads to a sensitivity increase from 614.5 nm/RIU to 765.4 nm/RIU, which we attribute to a stronger coupling between individual LSPRs at the hole edges with spatially extended SPPs. Our results can be used to increase the performance of TiN NHAs for applications in on-chip plasmonic refractive index sensors.

RDS: FPGA Routing Delay Sensors for Effective Remote Power Analysis Attacks

State-of-the-art sensors for measuring FPGA voltage fluctuations are time-to-digital converters (TDCs). They allow detecting voltage fluctuations in the order of a few nanoseconds. The key building component of a TDC is a delay line, typically implemented as a chain of fast carry propagation multiplexers. In FPGAs, the fast carry chains are constrained to dedicated logic and routing, and need to be routed strictly vertically. In this work, we present an alternative approach to designing on-chip voltage sensors, in which the FPGA routing resources replace the carry logic. We present three variants of what we name a routing delay sensor (RDS): one vertically constrained, one horizontally constrained, and one free of any constraints. We perform a thorough experimental evaluation on both the Sakura-X side-channel evaluation board and the Alveo U200 datacenter card, to evaluate the performance of RDS sensors in the context of a remote power side-channel analysis attack. The results show that our best RDS implementation in most cases outperforms the TDC. On average, for breaking the full 128-bit key of an AES-128 cryptographic core, an adversary requires 35% fewer side-channel traces when using the RDS than when using the TDC. Besides making the attack more effective, given the absence of the placement and routing constraint, the RDS sensor is also easier to deploy.

Manipulation Over Surface Waves in Bilayer Hyperbolic Metasurfaces: Topological Transition and Multidirectional Canalization

Spoof surface plasmon-polariton is a type of surface wave (SW) propagating at the artificially engineered structures in microwave and terahertz ranges. These SWs are highly important in planar photonic and on-chip devices, integrated circuits, lenses, sensors, and antennas applications. However, it is still a challenge to control the propagation regime of such SWs including the wavefront shapes and propagation directions. In this letter, we study the SWs in bilayer hyperbolic metasurfaces and show that the interplay between two layers allows them to manage their regime of propagation. We demonstrate the switching between the angle and number of propagation directions of SWs at the same frequency. Finally, we demonstrate experimentally the tunable multidirectional in-plane canalization of SWs by adjusting the directions of their propagation within the angular range from 0° to 12.8°. The discovered rotation-mediated interlayer coupling of hyperbolic metasurfaces paves the way toward efficient in-plane transfer of localized electromagnetic signals.

An Interface ASIC Design of MEMS Gyroscope with Analog Closed Loop Driving.

This paper introduces a digital interface application-specific integrated circuit (ASIC) for a micro-electromechanical systems (MEMS) vibratory gyroscope. The driving circuit of the interface ASIC uses an automatic gain circuit (AGC) module instead of a phase-locked loop to realize a self-excited vibration, which gives the gyroscope system good robustness. In order to realize the co-simulation of the mechanically sensitive structure and interface circuit of the gyroscope, the equivalent electrical model analysis and modeling of the mechanically sensitive structure of the gyro are carried out by Verilog-A. According to the design scheme of the MEMS gyroscope interface circuit, a system-level simulation model including mechanically sensitive structure and measurement and control circuit is established by SIMULINK. A digital-to-analog converter (ADC) is designed for the digital processing and temperature compensation of the angular velocity in the MEMS gyroscope digital circuit system. Using the positive and negative diode temperature characteristics, the function of the on-chip temperature sensor is realized, and the temperature compensation and zero bias correction are carried out simultaneously. The MEMS interface ASIC is designed using a standard 0.18 μM CMOS BCD process. The experimental results show that the signal-to-noise ratio (SNR) of sigma-delta (ΣΔ) ADC is 111.56 dB. The nonlinearity of the MEMS gyroscope system is 0.03% over the full-scale range.

Large-Scale direct numerical simulations of turbulence using GPUs and modern Fortran

We present our approach to making direct numerical simulations of turbulence with applications in sustainable shipping. We use modern Fortran and the spectral element method to leverage and scale on supercomputers powered by the Nvidia A100 and the recent AMD Instinct MI250X GPUs, while still providing support for user software developed in Fortran. We demonstrate the efficiency of our approach by performing the world’s first direct numerical simulation of the flow around a Flettner rotor at Re = 30,000 and its interaction with a turbulent boundary layer. We present a performance comparison between the AMD Instinct MI250X and Nvidia A100 GPUs for scalable computational fluid dynamics. Our results show that one MI250X offers performance on par with two A100 GPUs and has a similar power efficiency based on readings from on-chip energy sensors.

Pixel Super-Resolved Lensless on-Chip Sensor with Scattering Multiplexing

Lensless on-chip microscopy has shown great potential for biomedical imaging due to its large-area and high-throughput imaging capabilities. By combining the pixel super-resolution (PSR) technique, it can improve the resolution beyond the limit of the imaging detector. However, existing PSR techniques are restricted by the feature size and crosstalk of modulation components (such as spatial light modulator), which cannot efficiently encode target information. Besides, the reconstruction algorithms suffer from the trade-off between reconstruction quality, imaging resolution, and computational efficiency. In this work, we constructed a novel integrated lensless on-chip sensor via scattering multiplexing and reported a robust PSR algorithm for target reconstruction. We employed a scattering layer to replace conventional modulators and permanently integrated it with the image detector. Benefiting from the high-degree-of-freedom calibration, the scattering layer realized fine wavefront modulation with a small feature size. Besides, the integration engineering avoided repetitious calibration and reduced the complexity of data acquisition. The reported PSR algorithm combined both model-driven and data-driven strategies, with the advantages of high fidelity, strong generalization, and low computational complexity. The remarkable performance allows it to efficiently exploit the high-frequency information from the fine modulation. A series of experiments validate that the reported sensor and PSR algorithm provide a low-cost solution for large-scale microscopic imaging, realizing ∼1.1 μm imaging resolution and ∼7 dB enhancement on the PSNR index compared to existing methods.

Grating-assisted hybrid plasmonic slot resonator for on-chip SERS sensor with built-in filter

A grating-assisted hybrid plasmonic slot resonator is proposed and theoretically investigated as an on-chip surface-enhanced Raman scattering (SERS) sensor. A dielectric Bragg grating and a gold baffle are introduced into the hybrid plasmonic slot waveguide as two mirrors to form a plasmonic–dielectric cavity, in which the constructive interference of the input pump light greatly enhances the electric field. The grating reflects the wasted pump light for reverse secondary coupling and acts as a built-in notch filter for filtering out pump light from Raman scattered light simultaneously, improving the coupling efficiency and realizing a compact and miniaturized on-chip SERS sensor. Both the volumetric electric field enhancement and Raman collection efficiency are taken into account. The proposed scheme provides a simple, effective and universal method for improving the performance of the plasmonic-antennas-type waveguide-based SERS sensors.

Ultra-compact and highly sensitive refractive index sensor based on a chalcogenide suspended slot hybrid plasmonic microring resonator

A microring resonator based on chalcogenide suspended slot hybrid plasmonic waveguide (CSSHPW) is designed for the refractive index (RI) sensing. The CSSHPW consists of a suspended Si nanowire with a nanoscale air gap and a Cu film deposited on a chalcogenide support layer. The mode characteristics of the suspended slot hybrid plasmonic mode (SSHPM) in the CSSHPW are simulated by using the finite element method (FEM). The simulation results show that the waveguide sensitivity (Swg) as high as 0.8 and the optical propagation loss as low as 0.08 dB/µm are obtained by optimizing the structure. The RI sensitivity (S), detection limit (DL), and detection range (DR) of the CSSHPW-based microring resonator (MRR) with a radius of 2 µm are 511.5 nm/RIU, 4.72 × 10−5 RIU, and 0.158 RIU, respectively. These superior performances as well as the fully complementary metal-oxide-semiconductor (CMOS) compatibility pave the way for CSSHPW-based biochemical sensors to realize on-chip high-S waveguide sensors. Moreover, the CSSHPW-MRR has a small size, high modulation depth, large Swg, and Cu cap of easy electrode formation, it facilitates the fabrication of a high-performance electro-optic (EO) modulator by infilling the slot with EO material.

Spoof surface plasmon polaritons based on-chip sensor for dielectric detection.

A compact millimeter-wave on-chip sensor for dielectric detection is presented using gallium arsenide technology based on spoof surface plasmon polaritons (SSPPs). The proposed structure is developed from traditional half-mode substrate integrated waveguide (HMSIW) and its dispersion characteristics is analyzed through electromagnetic simulations. Consequently, the operating frequency and bandwidth of the on-chip sensor can be easily adjusted, which provides more flexibility for the practical application of the sensor. The linear sensing for relative dielectric constant of the film materials is acquired, with thickness-insensitive property. Moreover, the low coupling to the nearby components can be achieved due to the strong field confinement characteristics of the SSPPs, which is of great significance in the application scenarios of on-chip integrated circuits for the suppression of electromagnetic interference.

On-chip CuFe2O4 nanofiber for conductometric NO2 and H2S gas-sensors

xCuO-(1-x)Fe2O3 composite nanofibers (NFs) for gas-sensing applications were thoroughly investigated in this work employing on-chip electrospinning. The fabricated NFs had a characteristic spider-net-like morphology and had diameters of 50–100 nm. The NFs composed of nanograins with diameters ranging from 16 to 35 nm have multi-porous structures. The composite NFs enhanced sensor response compared to that of single metal oxides. At the optimal composition of 0.5CuO-0.5Fe2O3 NFs, which formed a complex oxide of copper ferrite (CuFe2O4), the sensor showed the highest response (15.3 and 10) to 1 ppm H2S gas at 350 °C and 10 ppm NO2 gas at 300 °C, respectively. Additionally, the detection of on-chip NF sensors to target gases was considerably impacted by the electrospinning time. The maximum response to H2S gas was achieved after 30 min of the electrospinning process, while that to NO2 gas is 10 min. The enhanced gas-sensing performance was attributed to nanograin-based NF structure, the formation of binary complex CuFe2O4 oxide, and the heterojunctions between CuFe2O4 and single oxide (CuO or α-Fe2O3) in composite NFs. Furthermore, the high sensitivity and selectivity of the CuFe2O4 NF sensor toward target gases are also discussed by using density functional theory (DFT) calculation.