Search

Single atomically thick graphene, with unique structural flexibility, surface sensitivity, and effective light-mater interaction, has shown exceptional advances in optoelectronics. It opens a door for diverse functionalized photonic devices, ranging from passive polarizers to active lasers and parametric oscillators. Among them, graphene-fiber biochemical sensors combine the merits of both graphene and fiber structures, demonstrating impressively high performances, such as single-molecule detectability and fast responsibility. These graphene-fiber biochemical sensors can offer tools in various applications, such as gas tracing, chemical analysis, and medical testing. In this paper, we review the emerging graphene-fiber biochemical sensors comprehensively, including the sensing principles, device fabrications, systematic implementations, and advanced applications. Finally, we summarize the state-of-the-art graphene-fiber biochemical sensors and put forward our outlooks on the development in the future.

Refereed/Peer-reviewed A multiplexed fiber sensor is proposed based on Fabry-Perot interferometers formed by serially splicing C-shaped and single mode fibers. We first demonstrate multiplexed refractive index sensing by independently filling and measuring sodium chloride (NaCl) solutions with different concentrations in a two-cavity system. The results show minimal cross-talk between the two interferometers. The dual-cavity interferometric sensor was then applied to biochemical sensing by utilizing polyelectrolyte layer by layer self-assembly followed by the biotin-streptavidin binding mechanism. The proposed sensor solves an important problem in biochemical sensing by providing an ability to simultaneously measure a negative control, critical for reducing false positive measurements.

Wireless monitoring of the physio-biochemical information is becoming increasingly important for healthcare. In this work, we present a proof-of-concept hydrogel-based wireless biochemical sensing scheme utilizing ultrasound. The sensing system utilizes silica-nanoparticle embedded hydrogel deposited on a thin glass substrate, which presents two prominent interfaces for ultrasonic backscattering (tissue/glass and hydrogel/glass). To overcome the effect of the varying acoustic properties of the intervening biological tissues between the sensor and the external transducer, we implemented a differential mode of ultrasonic back-scattering. Here, we demonstrate a wireless pH measurement with a resolution of 0.2 pH level change and a wireless sensing range around 10 cm in a water tank.

A sickle-shaped metamaterial (SSM) based biochemical sensor with multiple resonances was investigated in the terahertz frequency range. The electromagnetic responses of SSM were found to be four resonances, namely dipolar, quadrupolar, octupolar and hexadecapolar plasmon resonances. They were generated from the interactions between SSM and perpendicularly incident terahertz waves. The sensing performances of SSM-based biochemical sensors were evaluated by changing ambient environments and analyte varieties. The highest values of sensitivity and figure of merit (FOM) for SSM covered with analyte thin-films were 471 GHz/RIU (refraction index unit) and 94 RIU&minus, 1, respectively. In order to further investigate the biosensing ability of the proposed SSM device, dielectric hemispheres and microfluidic chips were adopted to imitate dry and hydrous biological specimens, respectively. The results show that the sensing abilities of SSM-based biochemical sensors could be enhanced by increasing either the number of hemispheres or the channel width of the microfluidic chip. The highest sensitivity was 405 GHz/RIU for SSM integrated with microfluidic chips. Finally, three more realistic models were simulated to imitate real sensing situations, and the corresponding highest sensitivity was 502 GHz/RIU. The proposed SSM device paves the way to possible uses in biochemical sensing applications.

International audience; This paper presents the interest of a highly sensitive biosensor coated with a TiO2 mesoporous film as sensitive layer. The main novelty is related to the modelling of the device and simulation by using Finite Element Method with COMSOL Multiphysics software, as a good way to take into account the physical properties of porous 3D-layers. The strategy of using such Love wave devices, with 3D porous layers, offering further easy functionalization, aims not only to increase the amount of targets caught on the sensor surface, but also to enhance the detection mechanism by a higher perturbation of the Love wave acoustic energy which could be trapped inside the 3D sensitive layer. First, as a proof of concept, experimental devices with a 3D titania mesoporous layer were realized, and they have shown a good agreement with simulated results. Furthermore, experimental test with several Newtonian liquids are investigated, in a range of viscosities from 1 to 7 cP, typical of those concerned by our biochemical applications. The sensitivity with a 300 nm thick porous sensing layer was 10 times that of the bare device, with interesting dynamical issues to be further studied, giving rise to the great potentialities of such architectures for biological detection of low weight biochemical targets.

The tilted fiber Bragg grating (TFBG) is a new kind of fiber-optic sensor that possesses all the advantages of well-established Bragg grating technology in addition to being able to excite cladding modes resonantly. This device opens up a multitude of opportunities for single-point sensing in hard-to-reach spaces with very controllable cross-sensitivities, absolute and relative measurements of various parameters, and an extreme sensitivity to materials external to the fiber without requiring the fiber to be etched or tapered. Over the past five years, our research group has been developing multimodal fiber-optic sensors based on TFBG in various shapes and forms, always keeping the device itself simple to fabricate and compatible with low-cost manufacturing. This paper presents a brief review of the principle, fabrication, characterization, and implementation of TFBGs, followed by our progress in TFBG sensors for mechanical and biochemical applications, including one-dimensional TFBG vibroscopes, accelerometers and micro-displacement sensors; two-dimensional TFBG vector vibroscopes and vector rotation sensors; reflective TFBG refractometers with in-fiber and fiber-to-fiber configurations; polarimetric and plasmonic TFBG biochemical sensors for in-situ detection of cell, protein and glucose.

This paper presents a brief overview of the technologies used to implement surface plasmon resonance (SPR) effects into fiber-optic sensors for chemical and biochemical applications and a survey of results reported over the last ten years. The performance indicators that are relevant for such systems, such as refractometric sensitivity, operating wavelength, and figure of merit (FOM), are discussed and listed in table form. A list of experimental results with reported limits of detection (LOD) for proteins, toxins, viruses, DNA, bacteria, glucose, and various chemicals is also provided for the same time period. Configurations discussed include fiber-optic analogues of the Kretschmann–Raether prism SPR platforms, made from geometry-modified multimode and single-mode optical fibers (unclad, side-polished, tapered, and U-shaped), long period fiber gratings (LPFG), tilted fiber Bragg gratings (TFBG), and specialty fibers (plastic or polymer, microstructured, and photonic crystal fibers). Configurations involving the excitation of surface plasmon polaritons (SPP) on continuous thin metal layers as well as those involving localized SPR (LSPR) phenomena in nanoparticle metal coatings of gold, silver, and other metals at visible and near-infrared wavelengths are described and compared quantitatively. Graphical AbstractArtist rendering of light from a tilted fiber Bragg grating probing the cladding surface where a thin gold film and biofunctional layer are used to detects analytes

This work presents different circuit architectures that combine sensing and signal readout functions. The basic building block is a Fin Field-Effect Transistor (Fin-FET) used as both sensor and metal gate transistor. Moreover, a hybrid partially gated FinFET is proposed as a unique device enabling the integration of digital gates with biosensing. Each device has been modeled using Verilog-A to explore different designs through Electronic Design Automation (EDA) simulations. A common-source amplifier has been demonstrated to be a simple circuit for the amplification of a threshold voltage shift upon, e.g., a pH change at the sensor surface. Using an enhancement-mode n-MOS transistor as load, an input variation ΔVth ≈ 60 mV/pH can be amplified up to ΔVout ≈ 1 V/pH with good linearity between pH 6 and 10. A depletion-mode n-MOS transistor load has been used to obtain a steeper transition in DC characteristics. By using a hybrid partially gated FinFET as a driving transistor a sensing NOR logic gate has been shown. The use of such hybrid FinFETs allows for building multi-stage circuits. Two examples of such circuits, capable of both sensing and signal conditioning, have been explored and discussed here. The first circuit is a ring oscillator whose oscillating frequency depends on the analyte concentration, i.e., on the voltage drop in the liquid. The second is a pseudo-differential amplifier for differential measurements with tunable gain. The linearity and the sensitivity of the different designs are analyzed for various applications. To the best of our knowledge, no FinFET-based circuits featuring both sensing and readout capabilities have been previously reported.

While organic semiconductors are being widely investigated for chemical and biochemical sensing applications, major drawbacks such as the poor device stability and low charge carrier mobility in aqueous electrolytes have not yet been solved to complete satisfaction. In this work, solution-gated organic field-effect transistors (SGOFETs) based on the molecule α,ω-dihexyl-sexithiophene (DH6T) are presented as promising platforms for in-electrolyte sensing. Thin films of DH6T were investigated with regard to the influence of the substrate temperature during deposition on the grain size and structural order. The performance of SGOFETs can be improved by choosing suitable growth parameters that lead to a two-dimensional film morphology and a high degree of structural order. Furthermore, the capability of the SGOFETs to detect changes in the pH or ionic strength of the gate electrolyte is demonstrated and simulated. Finally, excellent transistor stability is confirmed by continuously operating the device over a period of several days, which is a consequence of the low threshold voltage of DH6T-based SGOFETs. Altogether, our results demonstrate the feasibility of high performance and highly stable organic semiconductor devices for chemical or biochemical applications., This work has been partially supported by the Nanosystems Initiative Munich (NIM) and the Deutsche Forschungsgemeinschaft (DFG) through the SFB 1032.

International audience; This work reports the design and fabrication of silicon nitride-based microresonators by employing DUV optical lithography and ICP-RIE plasma etching. Microring devices with high Q factors provide high sensitivity and low detection limit, enabling their use in biochemical sensing applications. With these properties, the devices can be used to detect and quantify the biomolecules present in a homogeneous solution, by detecting an effective refractive index change, without using fluorescent labels.

Light manipulation has always been the fundamental subject in the field of optics since centuries ago. Traditional optical devices are usually designed using glasses and other materials, such as semiconductors and metals. Optofluidics is the combination of microfluidics and optics, which brings a host of new advantages to conventional solid systems. The capabilities of light manipulation and biochemical sensing are inherent alongside the emergence of optofluidics. This new research area promotes advancements in optics, biology, and chemistry. The development of fast, accurate, low-cost, and small-sized biochemical micro-sensors is an urgent demand for real-time monitoring. However, the fluid flow in the on-chip sensor is usually non-uniformed, which is a new and emerging challenge for the accuracy of optical detection. It is significant to reveal the principle of light propagation in an inhomogeneous liquid flow and the interaction between biochemical samples and light in flowing liquids. In this review, we summarize the current state of optofluidic lab-on-a-chip techniques from the perspective of light modulation by the unique dynamic properties of fluid in heterogeneous media, such as diffusion, heat transfer, and centrifugation etc. Furthermore, this review introduces several novel photonic phenomena in an inhomogeneous liquid flow and demonstrates their application in biochemical sensing.

Optical fibre gratings have recently been suggested as optical platforms for chemical and biochemical sensing. On the basis of the measurement of refractive index changes induced by a chemical and biochemical interaction in the transmission spectrum along the fibres, they are proposed as a possible alternative to the other label-free optical approaches, such as surface plasmon resonance and optical resonators. The combination of the use of optical fibres with the fact that the signal modulation is spectrally encoded offers multiplexing and remote measurement capabilities which the other technology platforms are not able to or can hardly offer. The fundamentals of the different types of optical fibre gratings are described and the performances of the chemical and biochemical sensors based on this approach are reviewed. Advantages and limitations of optical fibre gratings are considered, with a look at new perspectives for their utilization in the field.