This study aims to evaluate the effects of total ionizing dose (TID) radiation on the performance of n-MOSFET current mirrors. We propose an ovel experimental approach to analyze the interaction between charge trapping in the MOSFET gate oxide and the resulting current mirror degradation by subjecting devices to TID doses from 50 krad(Si) to 300 krad(Si) using a 60Co gamma source Experimental data show that threshold voltage shifts by up to 1.31 V and transconductance increases by 27%. This degradation leads to this a reduction of more than 10% in current mirror output accuracy occurs at the highest dose. These quantitative criteria establish a clear benchmark for assessing the impact of TID on current mirror performance. These effects are attributed to positive charge trapping in the gate oxide and at the Si-SiO2 interface induced by ionizing radiation. This study focuses exclusively on radiation effects; electrical stress phenomena such as over-voltage or electrostatic discharge (ESD) are not addressed. The results highlight the critical importance of accounting for TID effects when designing high-performance n-MOSFET current mirrors for radiation-hardened applications.

This work reports on the development of a micromachined monolithic single-axis electromagnetic accelerometer based on the relative motion between the windings of a concentric planar transformer, whose internal inductor is suspended. The mechanical and electromagnetic modelling of the sensor is presented, as well as the implementation of a virtual read-out circuit. Electromagnetic simulations were used to extract the electrical performance parameters in the form of a lumped-element model. The results demonstrate that rotation between the two windings leads to an approximately linear variation in the mutual inductance. Furthermore, measurement circuit simulations revealed that the sensor could achieve an in-plane acceleration sensitivity of 32.9 mV/g for a matched network when excited with 3Vpp, 100 MHz excitation voltage.

Since graphene has a unique band structure with the valence and conduction bands touching each other at a single point called the Dirac point, this makes it extremely sensitive to the surroundings such as doping, external electric field, mechanical deformation, etc. Hence, it is very desirable for sensing applications. However, its surface inertness poses significant drawbacks. Therefore, it is necessary to treat the graphene surface to bind biomolecules. In this paper, we report the use of amine-functionalized graphene by plasma polymerization to detect the presence of biomolecules in graphene channel based on a liquid-gate field-effect transistor (LG-GFET). Taking streptavidin and biotin as an example, the binding interactions of streptavidin–biotin complexes are detected by monitoring the shift of the Dirac point. By varying the streptavidin concentrations from 0.1 nM to 1000 nM, we found that our LG-GFET achieves detection capabilities as low as 0.1 nM. Our approach can be applied for the detection of biological molecules with low detection limit, high sensitivity, and stability.

The design of a porous silicon (PSi) biosensor is not often documented, but is of the upmost importance to optimize its performance. In this work, the motivation behind the design choices of a PSi-based optical biosensor for the indirect detection of bacteria via their lysis is detailed. The transducer, based on a PSi membrane, was characterized and models were built to simulate the analyte diffusion, depending on the porous nanostructures, and to optimize the optical properties. Once all performances and properties were analyzed and optimized, a theoretical response was calculated. The theoretical limit of detection was computed as 104 CFU/mL, based on the noise levels of the optical setup. The experimental response was measured using 106 CFU/mL of Bacillus cereus as model strain, lysed by bacteriophage-coded endolysins PlyB221. The obtained signal matched the expected response, demonstrating the validity of our design and models.

This paper presents an innovative approach to integrate a high-quality porous silicon (PSi) waveguide on ultra-low-resistivity (ULR) substrates for terahertz (THz) applications. Eliminating the need for deep etching and multiple wafer bonding, the proposed technique leverages the low resistivity of ULR substrate and the high resistivity of PSi to create an efficient waveguide. Simulations and preliminary experiments validate the concept.

This article presents two adaptive biasing techniques for comparators to achieve ultralow-power and high dynamic range in readout circuits for resistive gas sensors. The first technique is based on an on-demand biasing that generates a bias current up to $3 \mu \text{A}$ when the differential input voltage is close to zero, while minimizing the bias current when a comparison is not imminent. The second technique takes advantage of the correlation between sensor current and delay requirements to bias the comparator with the appropriate current for each situation. These techniques were applied to two readout circuits, demonstrating a reduction of the energy per measurement to less than a fifth for the largest input resistance in comparison to fixed biasing without affecting SNR. The input range is above five decades in both cases, from 2.4 $\text{k}\Omega $ up to 1 $\text{G}\Omega $ and from 1 $\text{k}\Omega $ up to 270 $\text{M}\Omega $ . The signal to noise ratio ranges from 55 dB up to 70 dB which provides enough margin to interface a wide range of gas sensors. Lastly, one of the designs was successfully employed to measure varying concentrations of ammonia with a polypyrrole (PPy) gas sensor.

In this work, we developed a biosensor for the indirect detection of bacteria via their lysate. The developed sensor is based on porous silicon membranes, which are known for their many attractive optical and physical properties. Unlike traditional porous silicon biosensors, the selectivity of the bioassay presented in this work does not rely on bio-probes attached to the sensor surface; the selectivity is added to the analyte itself, by the addition of lytic enzymes that target only the desired bacteria. The resulting bacterial lysate is then able to penetrate into the porous silicon membrane and affects its optical properties, while intact bacteria accumulate on top of the sensor. The porous silicon sensors, fabricated using standard microfabrication techniques, are coated with TiO2 layers using atomic layer deposition. These layers serve as passivation but also enhance the optical properties. The performance of the TiO2-coated biosensor is tested for the detection of Bacillus cereus, using the bacteriophage-encoded PlyB221 endolysin as the lytic agent. The sensitivity of the biosensor is much improved compared to previous works, reaching 103 CFU/mL, with a total assay time of 1 h 30 min. The selectivity and versatility of the detection platform are also demonstrated, as is the detection of B. cereus in a complex analyte.

This paper demonstrates a procedure for complete in-situ recovery of on-membrane CMOS devices from total ionizing dose (TID) defects induced by gamma radiation. Several annealing steps were applied using an integrated micro-heater with a maximum temperature of 365 degrees C. The electrical characteristics of the on-membrane nMOSFET are recorded prior and during irradiation (up to 348 krad (Si)), as well as after each step of the in-situ thermal annealing. High-resolution current sampling measurements reveal the presence of oxide defects after irradiation, with a clear dominant single-trap signature in the random telegraph noise (RTN) traces. Drain current over time measurements are used for the trap identification and further for the defects' parameters extraction. The power spectral density (PSD) curves confirm a clear dominance of the RTN behavior in the low-frequency noise. A radiation-induced oxide trap is detected at 5.4 nm from the Si-SiO2 interface, with an energy of 0.086 eV from the Fermi level in the bandgap. After annealing, the RTN behavior vanishes with a further important reduction of flicker noise. Low-frequency noise measurements of the transistor confirmed the neutralization of oxide defects after annealing. The electro-thermal annealing of the nMOSFET allows a total recovery of its original characteristics after being severely degraded by radiation-induced defects.

Hydrogen sulfide is a toxic, highly corrosive and pollutant gas, but also a key-biomarker in disease diagnosis trough breath analysis. Its detection at very low level is therefore relevant and can be achieved with chemiresistors. The present work proposes a solution consisting in a facile synthesis of CuO-loaded SnO2 hollow nanospheres deposited on interdigitated electrodes (IDEs). Synthesis, chemical and electrical character-ization, deposit process of the sensing layer and gas sensing capabilities of the sensing platform are presented. CuO loaded Sno2 sensing platforms achieved a successful sub-ppm detection at an operating temperature of 100 degrees Celsius.

New gas sensing materials, like conductive polymers and nanomaterials-based composites, together with integrated circuit advancements have enabled a new paradigm in gas sensing where a matrix of different types of sensors is used to improve selectivity and sensitivity. In this paper we present a highly flexible read-out circuit for acquiring the dc resistance of the sensors in the matrix. It can measure values from 1 $\text{k}\Omega $ up to 33 $\text{M}\Omega $ , with a minimum SNR of 57 dB. It also offers a wide range of input configuration in terms of resistance and bias voltages to select the optimal bias point for each sensor and to accommodate a large range of sensor types. It achieves very low power consumption at a maximum current consumption of $194~\mu \text{A}$ and an energy per conversion ranging from 1.21 nJ up to 188 nJ thanks to the optimization of the frequency of operation. The circuit was fabricated in a 180 nm bulk CMOS process and a complete characterization of the circuit is presented including current consumption, signal-to-noise ratio, and transfer function. Finally, the circuit was tested in a real application for the measurement of NH3 and NO2 using two different types of sensors validating the design objectives and the capability of the read-out circuit for system-on-chip integrations.

A robust fabrication method for stable mesoporous silicon membranes using standard microfabrication techniques is presented. The porous silicon membranes were passivated through the atomic layer deposition of different metal oxides, namely aluminium oxide Al2O3, hafnium oxide HfO2 and titanium oxide TiO2. The fabricated membranes were characterized in terms of morphology, optical properties and chemical properties. Stability tests and optical probing noise level determination were also performed. Preliminary results using an Al2O3 passivated membranes for a biosensing application are also presented for selective optical detection of Bacillus cereus bacterial lysate. The biosensor was able to detect the bacterial lysate, with an initial bacteria concentration of 106 colony forming units per mL (CFU/mL), in less than 10 min.

In this study, different planar inductor topologies were studied to evaluate their characteristic parameters’ variation range upon approaching Fe- and Cu-based shield plates. The use of such materials can differently alter the electrical properties of planar inductors such as the inductance, resonant frequency, resistance, and quality factor, which could be useful in multiple devices, particularly in inductive sensing and radio-frequency (or RF) applications. To reach an optimal design, five different square topologies, including spiral, tapered, non-spiral, meander, and fractal, were built on a printed circuit board (PCB) and assessed experimentally. At the working frequency of 1 MHz, the results showed a decrease in the inductance value when approaching a Cu-based plate and an increase with Fe-based plates. The higher variation range was noticeable for double-layer topologies, which was about 60% with the Cu-based plate. Beyond an intrinsic deflection frequency, the inductance value began to decrease when approaching the ferromagnetic plate because of the ferromagnetic resonance (FMR). It has been shown that the FMR frequency depends on the inductor topology and is larger for the double-layer spiral one. The Q-factor was decreasing for all topologies but was much faster when using ferromagnetic plates because of the FMR, which intensely increases the track resistance. The resonant frequency was increasing for all double-layer topologies and decreasing for single-layer ones, which was mainly due to the percentage change in the stray capacitance compared to the inductance variation. The concept of varying inductors by metal shielding plates has great potential in a wide range of nondestructive sensing and RF applications.

Porous silicon (PSi) has been widely used as a biosensor in recent years due to its large surface area and its optical properties. Most PSi biosensors consist in close-ended porous layers, and, because of the diffusion-limited infiltration of the analyte, they lack sensitivity and speed of response. In order to overcome these shortcomings, PSi membranes (PSiMs) have been fabricated using electrochemical etching and standard microfabrication techniques. In this work, PSiMs have been used for the optical detection of Bacillus cereus lysate. Before detection, the bacteria are selectively lysed by PlyB221, an endolysin encoded by the bacteriophage Deep-Blue targeting B. cereus. The detection relies on the infiltration of bacterial lysate inside the membrane, which induces a shift of the effective optical thickness. The biosensor was able to detect a B. cereus bacterial lysate, with an initial bacteria concentration of 105 colony forming units per mL (CFU/mL), in only 1 h. This proof-of-concept also illustrates the specificity of the lysis before detection. Not only does this detection platform enable the fast detection of bacteria, but the same technique can be extended to other bacteria using selective lysis, as demonstrated by the detection of Staphylococcus epidermidis, selectively lysed by lysostaphin.

Porous silicon (PSi) research has been active for several decades. The multiple properties and structural features of PSi have made it a promising material for a wide variety of applications, going from drug delivery to microelectronics. By removing the bulk silicon below a PSi layer and creating a membrane, a whole new set of physical and chemical characteristics as well as potential uses have been discovered. In this review, recent works on Porous silicon membranes (PSiMs) are analysed and summarised. An updated overview of the progress made in several areas is presented with the purpose of highlighting PSiM's potential. New methods for the fabrication and the integration of PSiMs have been developed, relying more and more on semiconductors microfabrication techniques. Likewise, the properties of PSiMs have been extensively studied, enabling the emergence of a multitude of PSiM-based systems. A critical analysis of the advantages and disadvantages of this material is made, with the emphasis on the integration challenges that PSiMs are facing for future industrialisation.

The paper reports on fabrication processes related to low-cost manufacturing and integration of microfluidic biomedical detection systems fabricated without a cleanroom. First, we developed and demonstrated a process for manufacturing a microfluidic device. Second, we demonstrated a low temperature assembly technique for the packaging of the surface acoustic wave (SAW) sensor die. Sequentially, we demonstrated a low temperature process for the integration of the microfluidic device with a SAW sensor to form a fully functional biomedical detection system. The microfluidic device was manufactured by mechanical micromilling technology that is rapid, conceptually simple and a low-cost process. It is suitable for both prototyping and for a low and a medium scale production to address a niche market that is typical for the intended application. That technology has no specific requirement for a certified clean room environment. Unlikely other technology, such as molding and photolithography, for example, it has a shorter lead-time from design to manufacturing. The assembly technique for a SAW sensor is a carefully selected combination of known and matured processing steps causing no damage to a sensitive biofunctionalization on the sensor. The developed and demonstrated integration process for the in-house manufactured microfluidic device and the SAW sensor is a purely low temperature process that prevents a biological material deposited on the SAW sensor from degradation. Biocompatibility issues were also addressed during the study reported. Finally, we performed an ultrasonic (US) impedance characterization of the fully assembled system and demonstrated that neither the microfluidic system integrated on the sensor nor the integration process itself have an impact on the US impedance of the SAW sensor. That means that it does not affect the sensor performance. (c) 2021 Elsevier B.V. All rights reserved.

The rapid detection of hazardous bacteria is important for healthcare situations, where such identification can lead to substantial gains for patient treatment and recovery and a reduced usage of broad-spectrum antibiotics. Potential biosensors must be able to provide a fast, sensitive and selective response with as little sample preparation as possible. Indeed, some of these pathogens, such as Staphylococcus aureus, can be yet harmful at very low concentrations in the blood stream, e.g., below 10 colony forming units per mL (CFU/mL). These stringent requirements limit the number of candidates, especially for point-of-care applications. Amongst several biosensing techniques, optical sensing using porous silicon (PSi) substrate has been widely suggested in recent years thanks to unique features such as a large surface area, tunable optical characteristics, and above all relatively easy and affordable fabrication techniques. In most configurations, PSi optical biosensors are close-ended porous layers; this limits their sensitivity and responsiveness due to diffusion-limited infiltration of the analytes in the porous layer. Also, PSi is a reactive material, its oxidation in buffer solutions results in time-varying shifts. Despite its attractive properties, several challenges must still be overcome in order to reach practical applications. Our work addresses three main improvement points. The first one is the stability over time in saline solutions helped by atomic layer deposition of metal oxides inside the pores. Besides a better stability, our solution is helping with an increase of the optical signal to noise ratio, thus reducing the limit of detection. The second one is to perform the lysis of the bacteria prior to its exposure to the sensor, such that the selective detection is based upon the percolation of bacterial residues inside the pores rather than the bacteria themselves. The third one is to remove the bulk silicon below a PSi layer to create a membrane, that allows for flow-through of the analytes, thus enhancing the interactions between the lysate and the sensor’s surface. This approach allows us to avoid the step of surface functionalization used in classical biosensors. We tested thanks to these improvements the selective detection of Bacillus cereus lysate with concentrations between 103 and 105 CFU/mL. Future works are dedicated to further improvements, including optical signal enhancement techniques and dielectrophoretic assisted percolation in the porous silicon membrane.

This paper demonstrates a procedure for total insitu recovery of on-membrane n-type MOSFET from Total Ionizing Dose (TID) defects, due to the exposure to gamma radiation. After a total dose of 348 krad (Si), several annealing steps were applied using an integrated micro-heater with a maximum temperature of 364 °C. The electrical characteristics of the transistor are recorded initially in normal conditions, after irradiation and then after each step of the thermal annealing. The electro-thermal annealing of the transistor allowed a total recovery of the original characteristics after a major shift due to radiation-induced defects. Power Spectral Density (PSD) of noise measurements showed a clear domination of the Random Telegraph Noise (RTN) behavior due to the creation of oxide defects after irradiation. After annealing, the RTN behavior vanishes with a further important decrease of flicker noise. Low-frequency noise measurements of the transistor confirmed the neutralization of oxide defects after annealing.

In this work, we present a way to improve piezoresistive MOSFET strain gauges using Lock-In principle. This reduces the influence of 1/f-noise, showing a Limit of Detection (LoD) reduction from 474 (42) μϵ for current measurements to 40.5 (15) μϵ for Lock-In measurements at 10 μA (100μA) bias. This 1/f-noise reduction also allows for using more efficiently averaging, leading to a 50-fold improvement from 387 (30) μϵ for current measurements to 7.8 (2.4) μϵ for Lock-In, with 100 samples averaging.

Ultra-thin silicon-on-insulator-based sensors are presented, featuring a thickness of less than 20 μm, as new integrable items for wearable physical and physiological ultra-low-power applications. Depending on the Si thickness, the back contact realization and the bias conditions, they can be optimized for thermal sensing or optical sensing in the UV-VIS light band. A lateral PIN diode with a transparent graphene back gate shows a maximum responsivity of 0.18 A/W at 390 nm wavelength, and a high sensitivity of ~2.28 mV/°C at fixed 0.01 μA low bias current, whereas a vertical PN strip diode with an Al back contact extends the optical responsivity to the visible range (with e.g. 0.24 A/W at 555nm wavelength when biased at -2 V) and achieves a high-temperature sensitivity using constant reverse voltage method.