Biomimetic Sensor Research Articles

Molecular Imprinted Based Quartz Crystal Microbalance Sensors for Bacteria and Spores

A molecular imprinting strategy was combined with mass-sensitive transducers to generate robust and reliable biomimetic sensor systems for the detection of bioparticles. The patterning of polymers with bioanalytes enabled us to detect Escherichia coli (E. coli) bacteria with quartz crystal microbalance (QCM). The QCM sensor results were compared with direct Atomic Force Microscopy (AFM) measurements—bacteria cells adhering to the sensor coatings were counted. The recognition sites generated by Bacillus subtilis (B. subtilis) spores could successfully and reversibly recognize the template analyte and ensured rapid sensing. Cross sensitive measurements clearly showed the advantage of the molecular imprinting strategy, by which spores of Bacillus species (subtilis and thuringiensis) could easily be differentiated and selectively detected. The growth of B. subtilis from its spores was observed at 42 °C in appropriate nutrient solution of glucose and ammonium sulfate over a period of 15 h. Moreover, the growth of B. subtilis bacteria from its respective spores was studied by increasing the glucose concentration until saturation effect of the sensor. The polymeric sensor coatings were patterned to fix the B. subtilis in order to investigate osmotic effects according to a frequency response of 400 Hz by altering the ionic strength of 0.1 M.

Engineering a NO-Regulated Nanofluidic Sensor through the Cyclization Reaction Strategy.

Nitric oxide (NO) is known to be a secondary in vivo signaling agent, demonstrating various biological functions through regulating ion flux in channels. Considering the crucial role of NO in vivo, herein, a biomimetic NO-regulated nanofluidic sensor has been fabricated through a cyclization reaction strategy. This nanofluidic sensor exhibited a promising NO selectivity, sensitivity, and non-interference performance in complex matrices. Thus, such a NO-driven nanosensor will be meaningful for scientific researchers to grasp the in vivo functions of NO.

Biomimetic sensor based on Mn(III) meso-tetra(N-methyl-4-pyridyl) porphyrin for non-enzymatic electrocatalytic determination of hydrogen peroxide and as an electrochemical transducer in oxidase biosensor for analysis of biological media

Bioinspired molecular complexes that mimic the enzymatic catalysis of redox transformations offer a versatile platform for the development of non-enzymatic mediatorless sensors with high sensitivity, selectivity, and robustness without the use of precious metals. The aim of this study was to prepare and investigate biomimetic sensors based on the electrocatalytic reduction of hydrogen peroxide and oxygen by a series of immobilized complexes of iron and manganese with porphyrin macrocycles for the detection of hydrogen peroxide and glucose. The influence of substitution of the macroheterocyclic ligand, composition of the adsorption solution, Nafion membrane, and amino acids on the properties of the sensors was studied. Optimized sensor function is based on the electrogenerated reduced form of Mn(II) meso-tetra(N-methyl-4-pyridyl) porphyrin as a catalyst and allows high sensitivity of the hydrogen peroxide detection of 1.8 A M−1 cm−2 and 0.071 A M−1 cm−2 to be achieved in the lower and higher concentration ranges, respectively, with a low detection limit of 5⋅10−7 M at physiological pH 7.4 and in the presence of oxygen. The MnTMPyP electrode was investigated as an electrochemical transducer in the glucose-oxidase-based biosensor. The sensors were successfully applied for the detection of hydrogen peroxide and glucose in human serum samples. Along with a simple fabrication procedure and robustness of the sensor, the biomimetic electrocatalytic properties of the MnTMPyP complex facilitate excellent performance of the proposed sensors for hydrogen peroxide and glucose determination in biological media, emphasizing the importance of bioinspired electrocatalytic metalloporphyrin complexes for the development of sensors and point-of-care devices.

Computational design of molecularly imprinted polymer for electrochemical sensing and stability indicating study of sofosbuvir

In this work, a biomimetic electrochemical sensor for sofosbuvir (SOFO) was designed and optimized for its determination in pure forms, pharmaceutical formulations, urine besides forced degradation products. Computational calculations, based on density functional theory (DFT) at the B3LYP/6-31G(d) level, were initially employed to screen some of the commonly used electropolymerizable functional monomers including para-aminothiophenol (PTP), ortho-aminophenol (OAP), ortho-phenylenediamine (OPD), and pyrrole (PY). Based on the computational calculations, the imprinted sensor active sites were engineered via electropolymerization of OAP, which was found to show the highest binding efficiency to the target drug, on a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (f-MWCNTs) and reduced graphene oxide (RGO) nanocomposite for sensitive determination of SOFO. The fabrication variables of the sensor such as accumulation time, (f-MWCNTs&RGO) loading amount, number of electropolymerization cycles, variation of (template: monomer) ratio, pH, extraction solvent, and binding and rebinding conditions were optimized. The proposed electrchemical sensor was characterized using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM). Differential pulse voltammetry (DPV) was employed for obtaining the calibration curve and optimization of significant factors that control the sensor performance. To prepare the sensor, 2.5 µL of (f-MWCNTs&GO) were first casted on GCE where GO was reduced electrochemically to RGO followed by 20 electropolymerization cycles of a mixture that is (1:11) SOFO: OAP then a mixture of methanol and 0.5 M H2SO4 (4:1 V/V) can be used for template removal after almost 1 min of incubation with the sensor, while 5 min were enough for rebinding with SOFO once more at pH 7. The proposed sensor exhibited a linear range of (0.53–74.13) ng/mL and significant detection limit at 0.05 ng/mL (S/N = 3) using DPV in addition to good reproducibility and selectivity. Finally, the imprinted sensor was successfully applied for the analysis of SOFO in pure samples, urine, two different pharmaceutical formulations, and electrochemical stability indicating study.

A Deep-Learning Model for Underwater Position Sensing of a Wake's Source Using Artificial Seal Whiskers.

Various marine animals possess the ability to track their preys and navigate dark aquatic environments using hydrodynamic sensing of the surrounding flow. In the present study, a deep-learning model is applied to a biomimetic sensor for underwater position detection of a wake-generating body. The sensor is composed of a bundle of spatially-distributed optical fibers that act as artificial seal-like whiskers and interact with the body’s wake in the form of time-variant (bending) deflections. Supervised learning is employed to relate the vibrations of the artificial whiskers to the position of an upstream cylinder. The labeled training data are prepared based on the processing and reduction of the recorded bending responses of the artificial whiskers while the cylinder is placed at various locations. An iterative training algorithm is performed on two neural-network models while using the 10-fold cross-validation technique. The models are able to predict the coordinates of the cylinder in the two-dimensional (2D) space with a high degree of accuracy. The current implementation of the sensor can passively sense the wake generated by the cylinder at Re ≃ 6000 and estimate its position with an average error smaller than the characteristic diameter D of the cylinder and for inter-distances (in the water tunnel) up to 25-times D.

Development of a Passive Spore Sampler for Capture Enhancement of Airborne Crop Pathogens

Yellow rust spores currently blight commercial and domestic wheat production in areas of East Africa such as Ethiopia. Yellow rust is a hazard to crops which appears asymptomatic for a time, but inevitably causes significant losses in yield once symptoms of infection manifest themselves to the point where they can be readily observed by the naked eye. Regionally recurrent losses of up to 5% are common and reach as high as 25% in rare cases. Historically, spore sampling has been undertaken by large, cumbersome devices that require heavy power supplies and significant expertise to reliably operate. Moreover, tools for the design and development of such devices are currently limited. This paper, therefore, proposes design and testing processes to develop a spore sampling device that is compact, passive (requires no power to operate), and can better direct spores onto a biomimetic sensor platform enhancing the capture and detection of pathogens. This represents a novel design context for fluidic devices. Performance of the device has been simulated using Lagrangian particle tracking embedded into computational fluid dynamics (CFD) simulations, demonstrating significant improvements across a range of spore Stokes numbers. Experimental validation of numerical simulations was performed using wind tunnel testing and practical performance such as weathervaning was demonstrated. Results show that that the developed sampler is capable of enhancing the probability of yellow rust spores interacting with an internal sensor by a factor of between 20 and 25; demonstrating the effectiveness of the developed design.

Biomimetic sensor for ethambutol employing β-cyclodextrin mediated chiral copper metal organic framework and carbon nanofibers modified glassy carbon electrode

Stereochemical configuration of the drug is responsible for racemic switch with enantiomers in presence of chiral environment for human beings. Therefore, its determination in racemic and pharmaceutical samples becomes a challenge. Addressing this issue, an enantioselective electrochemical biomimetic sensor for discrimination of isomers of ethambutol (ETB) employing square wave voltammetry (SWV) is reported for the first time. For this purpose, a chiral host, β-Cyclodextrin based copper metal organic framework (CD-CuMOF) was synthesized and used for chelate complexation of ETB isomers (SS-ETB/RR-ETB). A glassy carbon electrode (GCE) is chemically modified using CD-CuMOF and carbon nanofibers (CNF) composite material to construct a sensor in the form of (CD-CuMOF-CNF-GCE). The behaviour of CD-CuMOF for ETB isomers on GCE is postulated to be an artificial enzyme model (AEM) as it mimics the catalytic activity similar to enzyme alcohol dehydrogenase for ETB. The biosensor exhibits excellent peak potential difference (ΔEp (SS-RR) = 108 mV) between ETB isomers using SWV showing a clear distinction in the racemic mixture. It showed a linear response in the range of 1.0 x 10-7 to 1 x 10-4 M and 5.0 x 10-7 to 2.5 x 10-4 M with low detection limit of 3.10 x 10-8 M and 8.52 x 10-8 M for RR-ETB and SS-ETB isomers respectively. The sensor was applied for the estimation of ETB isomers in racemic mixture and real samples viz., blood, urine and pharmaceutical. The CD-CuMOF is a low-cost material with higher stability than enzyme and offers an advantage for sensing and catalysis in future.

Biomimetic and porous nanofiber-based hybrid sensor for multifunctional pressure sensing and human gesture identification via deep learning method

Abstract Near-field electrospinning (NFES) is a site addressable microfabrication process and is utilized to deposit the micro/nano polyvinylidene fluoride (PVDF) fibers arrays on printed circuit board nanofiber-based based piezoelectric sensor architectures. In addition, a biomimetic and flexible hybrid self-powered sensors (BHSS) was created by hybridizing both Cu - biomimetic Polydimethylsiloxane triboelectric sensors to enhance the energy-harvesting characteristic. The optimized BHSS had open-circuit voltage (VOC) of 15 V and 115 nA of short-circuit current (ISC) and a maximum average power density is 675 μW m−2 with a load of 10 MΩ. Furthermore, an intelligent glove and the force sensor with are successively confirmed that the developed BHSS has promising applications in wearable self-power sensor technology. The machine learning algorithm of Long Short-Term Memory (LSTM) in the context of gesture recognition was used and effectively distinguish five human actions satisfactorily. LSTM based real-time electrical signals of five gestures dataset with varying duration and complexity can achieve an overall classification rate of 82.3%.

Research progress on new materials and properties of electronic skin

Human skin is an extraordinary organ; it comprises an integrated, stretchable network of sensors that transmits information to the brain about tactile and thermal stimuli, enabling us to safely and efficiently operate in our environment. Researchers have become interested in large-scale electronic device networks inspired by human skin, motivated by the prospect of developing devices such as autonomous smart robots and bionic prostheses. Developing electronic networks consist of flexible, stretchable, and robust devices that are compliant with large-scale implementation and integrated with multiple functionalities is a testament to the progress in developing human-skin like electronic bodies. In the fields of human physiological parameter detection and robot tactile perception, electronic skin has been commonly used as a kind of flexible tactile biomimetic sensor. Conventional electronic skin tactile sensors based on metal and semiconductor materials do not meet the requirements for stretchability and portability during actual use because of poor flexibility and wearability. Attributed to the rapid development of flexible materials, and manufacturing and sensing technologies, new materials such as polydimethylsiloxane (PDMS), carbon nanotubes, and graphene have been used to prepare or support electronic skin sensors in recent years, thus enabling electronic skin to be more similar to human skin in terms of stretchability, compressibility, and spatial resolution of touch, and other properties. Now, multi-functional integrated electronic skin devices have realized interaction with smart devices to obtain further collection and processing of human body information. This study analyzed and discussed new electronic skin materials and sensing technologies used in electronic skin, including capacitive effects, piezoelectric effects, piezoresistive effects, optical effects, and wireless antenna sensing. We focused on the recent research progress in electronic skin in terms of stretch/compressibility, biocompatibility, biodegradability, self-power, self-healing, temperature sensitivity, and multi-functional integration. Moreover, we anticipate the future research directions of new electronic skin properties and possible ways to achieve large-area, low-cost, multi-function integrated electronic skin sensor arrays.

Constructing stimuli-free self-healing, robust and ultrasensitive biocompatible hydrogel sensors with conductive cellulose nanocrystals

Self-healing conductive hydrogels as artificial skin-like materials hold great potential applications in the fields of artificial intelligence, soft robotics and personal healthcare. However, it remained challenging to construct stimuli-free self-healing biomimetic hydrogels with ultra-stretchability and excellent sensitivity. Herein, polyaniline (PANI) was coated on the surface polycarboxylic multi-branched cellulose nanocrystals (Multi CNC-PANI) via templated polymerization. Afterword, rod-like Multi CNC-PANI served as a dynamic bridge endowed those hydrogels hierarchical structure and dynamic hydrogen bond interactions doped with polyvinyl alcohol (PVA)/borax system. Combined with the dynamic borate ester bonds, the biomimetic nanocomposite hydrogels had high breaking strength (171.52 KPa), ultra-stretchability (1085%), rapid self-healing properties, adhesiveness, decent biocompatibility, and sensitivity. Especially, the hydrogels could keep good self-healing ability both in air and underwater without any stimuli, and the self-healing efficiency could reach up to 99.56% within 120 s. This hydrogel sensor could sensitively detect and distinguish human motions including swallow, fingers, wrist, elbow and knee joints, in real-time. Besides, the self-healed hydrogel gave detective signal with uniform and repeatable sensitivity, which endowed the hydrogels mechanically adaptability and good store stability. Therefore, the strategy may provide unique opportunities in designing biomimetic sensors with skin-like mechanical stretchability, sensitivity and self-healing properties.

Bioinspired Hydrophobic Cellulose Nanocrystal Composite Films as Organic-Solvent-Responsive Structural-Color Rewritable Papers.

Lots of beetles, moths, and birds in the natural world present stunning unique structural colors as well as excellent hydrophobic performances. Herein, a novel bioinspired variable structural-color film with organic-solvent responsiveness and surface hydrophobicity was fabricated. Cellulose nanocrystals (CNCs) provided structural color with left-handed helicity. PEG-PPG-PEG triblock copolymers (PPPTCs) were blended with CNCs, giving rise to the organic-solvent-responsive structural color and wider red-shift window of the reflectance peak. The color of the film could be regulated repeatedly under the stimulus of cyclohexanone with an obvious red shift up to 107 nm, corresponding to a macroscopic color change from blue to yellow. Low-surface-energy compound hexadecyltrimethoxysilane (HDTMS) was covalently grafted on the surface in a one-step method to introduce hydrophobicity, successfully preventing the effect of water on the ordered nanostructure. Based on the bionics principle, the as-prepared CNC/PPPTC nanocomposite films with variable structural colors and hydrophobicity are beneficial to their prospective applications in display screens, rewritable hydrophobic structural-color-changing paper, biomimetic sensors, and so forth.

Experimental Demonstration of Supervised Learning in Spiking Neural Networks with Phase-Change Memory Synapses

Spiking neural networks (SNN) are computational models inspired by the brain’s ability to naturally encode and process information in the time domain. The added temporal dimension is believed to render them more computationally efficient than the conventional artificial neural networks, though their full computational capabilities are yet to be explored. Recently, in-memory computing architectures based on non-volatile memory crossbar arrays have shown great promise to implement parallel computations in artificial and spiking neural networks. In this work, we evaluate the feasibility to realize high-performance event-driven in-situ supervised learning systems using nanoscale and stochastic analog memory synapses. For the first time, the potential of analog memory synapses to generate precisely timed spikes in SNNs is experimentally demonstrated. The experiment targets applications which directly integrates spike encoded signals generated from bio-mimetic sensors with in-memory computing based learning systems to generate precisely timed control signal spikes for neuromorphic actuators. More than 170,000 phase-change memory (PCM) based synapses from our prototype chip were trained based on an event-driven learning rule, to generate spike patterns with more than 85% of the spikes within a 25 ms tolerance interval in a 1250 ms long spike pattern. We observe that the accuracy is mainly limited by the imprecision related to device programming and temporal drift of conductance values. We show that an array level scaling scheme can significantly improve the retention of the trained SNN states in the presence of conductance drift in the PCM. Combining the computational potential of supervised SNNs with the parallel compute power of in-memory computing, this work paves the way for next-generation of efficient brain-inspired systems.

Development of an Ultra-Sensitive and Flexible Piezoresistive Flow Sensor Using Vertical Graphene Nanosheets

HighlightsA novel biomimetic flow sensor based on vertically grown graphene nanosheets with a mazelike structure is fabricated which closely mimics the structure of auditory hair cells.The proposed sensor demonstrated an ultra-high sensitivity of 103.91 mV (mm/s)−1, very low-velocity detection threshold (1.127 mm s−1), and excellent performance in a wide range of frequencies (0.1–25 Hz) for underwater sensing applications.The proposed sensor revealed a strong capability in development of an artificial lateral semicircular canal.

Deposition of Gold Nano-Micro Islands on Electrochemically Reduced Graphene Oxide to Use in Combination with Molecularly Imprinted Polymers

Molecularly imprinted polymers (MIPs) are known as an alternative for antibodies in immunosensors with high stability and low production cost. MIP approach relies on polymerization in the presence of a template molecule and subsequent template removal. In this process, the template molecule is exactly the same as the target molecule leading to a good selectivity for the biomimetic sensor [1]. The integration of MIPs with nanomaterials enables ultrasensitive sensors for various analytes. Besides, nanomaterials with uniform distribution and suitable morphology provide a wide linear range of detection for the sensor [1]. In particular, the controlled electrodeposition of gold can supply gold nano-micro islands (NMIs) with remarkable electrochemical behavior and high active surface area [2, 3]. However, it is found that the modification of an electrode surface using electrochemically reduced graphene oxide (ERGO), as a facile and fast method, not only increases the surface area but also improves its electrochemical behavior [4]. Herein, we describe a surface modification strategy based on indium tin oxide (ITO) electrode coated with ERGO to increase the surface active sites for nucleation and deposition of NMI. For this aim, we electrochemically reduced graphene oxide (GO) by one cycle in cyclic voltammetry (CV) with a scan rate of 100 mV s-1 in the range of -0.6 to -2 VAg/AgCl. The succeed of the electrochemical reduction was confirmed through ID/IG ratio in Raman spectroscopy and observing the enhanced electrochemical behavior in CV and electrochemical impedance spectroscopy (EIS) tests. The gold layers were deposited at 0 and -0.4 VAg/AgCl in 5, 50 and 100 mM HAuCl4 solutions for 50 and 300 s. The surface area of the resulted structures was also determined by integrating the reduction peak in CV tests in 50 mM H2SO4 solution [2]. The results showed that the gold structure deposited from 100 mM HAuCl4 at 0 VAg/AgCl for 50 s provided a significant surface area (0.47 cm2) on the electrode surface of 1 mm diameter, while this value for gold nanoparticles, as the common form of gold nanostructure in electrochemical biosensing, was determined only 0.063 cm2. This noticeable increase in surface area can result in a wide linear range of detection as well as excellent electrochemical behavior in biosensing applications. Scanning electron microscopy (SEM) of NMI structures deposited on both ITO and ERGO/ITO electrodes indicated a shrub-like structure because of the concentration polarization governed during gold deposition. Transmission scanning electron microscopy (TEM) of the NMI displayed Au (113) as the main crystalline plane. Based on the chronoamperometry plots, the gold deposition mechanism on the surface of both electrodes was according to the instantaneous deposition mode [2]. However, the electrode background surface indicated that the ERGO/ITO was uniformly covered by gold. This was attributed to the higher nucleation sites on the ERGO-modified electrode, which was confirmed by the increase of double-layer formation time (tmax). Accordingly, several nucleation stages on the chronoamperometry plot during NMI deposition on the ERGO/ITO electrode, were related to the formation of gold shrub-like structures with more needle-shaped structures. Finally, electropolymerization of a thin layer of o-phenylenediamine in the presence of Heart-fatty acid binding protein (H-FABP) as the template molecule and its subsequent removal was applied to make a biomimetic sensor. In this study, we demonstrated that the biomimetic developed electrode with high surface area, low production cost, and facile and fast synthesis method is acceptably selective to H-FABP against other cardiac biomarkers and serum proteins.KEYWORDS: Electrodeposition; Electrochemically reduced graphene oxide; Electrochemical sensors; Gold nano-micro islands; Molecularly imprinted polymers.

Foveal scanning based on an optical-phases array.

We utilize the space-variant structure of the human fovea as a basis for a novel, to the best of our knowledge, foveal approach based on optical-phases array (OPA). This approach can be used to solve issues in 3D imaging and achieve a large field of view and high resolution with real-time application. A foveal scanning model based on the OPA is established. Simulations and experiments are performed to verify the models and illustrate the advantages of foveal scanning compared with traditional raster scanning. Simulations agree well with the theory, and the foveal approach has higher efficiency than traditional raster scanning. These results can serve as a reference for developing biomimetic sensors that mimic the human eye.

Massive Growth of Graphene Quartz Fiber as a Multifunctional Electrode.

Quartz fiber, a widely used reinforcer with high tensile strength and excellent heat resistance, can have more attractive electrical applications such as electromagnetic interference shielding, static dissipation, and strain sensing if it becomes conductive. Many attempts have been made to increase the electrical conductivity of quartz fiber by surface coating of conductive polymers or plating of metal films, but suffers from sacrificing flexibility and causing heavy metal pollution. Here we designed and massively produced a hybrid structure of graphene quartz fiber (GQF) by a forced-flow chemical vapor deposition (CVD) method, which combines the excellent conductivity of graphene and the extraordinary properties of quartz fiber. The as-fabricated flexible GQF exhibited high sensitivity, fast response (<0.5 s) and good durability (∼5000 cycles) to organic solvent vapor, suitable as a real-time biomimetic gas sensor. Furthermore, the massively produced GQFs can be knitted into meter-scale fabrics with tunable conductivity (sheet resistances of 0.2-10 kΩ/sq) and superior electrothermal conversion efficiency (up to 980 °C within a few seconds at 24 V), thus propelling its promising application in industrial electric heaters. We expect this hybrid GQF material will greatly expand the applications of traditional quartz fiber into an infusive multifunctional regime.

Biomimetic sensors targeting oxidized-low-density lipoprotein with molecularly imprinted polymers

Oxidized-low-density lipoprotein (oxLDL) is well-recognized as an actual patho-atherogenic lipoprotein: elevated serum concentration of oxLDL increases the risk for developing atherosclerosis, leading to coronary artery disease (CAD). Herein, we report an approach for sensing oxLDL directly in serum with molecularly imprinted polymer (MIP) thin films on quartz crystal microbalance (QCM). The resulting MIP sensors show low cross-reaction toward low-density lipoprotein (LDL) and high-density lipoprotein (HDL): signals are around one magnitude smaller. Very-low-density lipoprotein (VLDL) and human serum albumin (HSA) do not lead to any significant sensor response. The sensor allowed for accurately assessing oxLDL over the detection range of 86–5600 μg dL−1, which covers the clinically relevant concentrations. The sensor determines oxLDL with recovery accuracy of 92–107% and a precision of 1–8% coefficient variation. Compared with commercially available oxLDL ELISA test kit our sensor reveals similar characteristics obtaining a correlation coefficient of 0.98. However, the sensors have rapid response times of 10 min compared to 210 min of ELISA, which demonstrates their efficiency in assessing this sensitive atherogenic biomarker for CAD diagnostics.

Manganese-doped tremella-like nickel oxide as biomimetic sensors toward highly sensitive detection of glucose in human serum

Tremella-like Mn-doped NiO nanomaterials (Mn-NiO) were synthesized via a simple hydrothermal process followed by calcination and then applied for biomimetic glucose sensing in an alkaline condition. Compared with regular NiO-based sensor, the Mn-NiO-based sensor performs higher electrocatalytic performance toward glucose oxidation reaction, which could be ascribed to a synergistic effect of Mn doping and tremella-like physical nanostructure. In more detail, Mn doping results in alteration of the surface electronic structure to promote the electro-oxidation activity, while the tremella-like nanostructure of NiO increases the electrochemical reaction surface area. This enzyme-free biomimetic glucose sensor demonstrates a high sensitivity of 3212.52 μA·mM−1·cm−2, fast response time (< 5 s), low limit of detection of 0.8 μM (S/N = 3) and long-term stability for glucose detection, along with reliable results in the human serum analysis. This work offers a facile approach to make a unique tremella-like nanostructure with specifically doped element to construct a biomimetic sensor with high electro-catalytic activity.

A biomimetic photonic crystal sensor for label-free detection of urinary venous thromboembolism biomarker

This work reports a novel label-free sensor combining photonic crystals and molecularly-imprinted polymer materials for targeting a protein in human samples within levels of clinical interest. This concept was applied to detect fibrinopeptide B (FPB) in urine, a biomarker of venous thromboembolism, which is a disease of great concern and demands innovative point-of-care devices for improved diagnosis.The molecularly-imprinted photonic polymer (MIPP) was obtained by tailoring an imprinted polymer on highly ordered silica nanoparticles assembled by vertical deposition. Owing to the hierarchical structure, the resulting MIPP exhibited optical properties that changed upon rebinding of the target analyte, FPB. Thus, the changes in reflectance intensity enabled a rapid and sensitive detection of FPB in human urine. The observed response was linear between 0.2 ng mL−1 and 22 ng mL-1 and showed a limit of detection of 0.13 ng mL-1. These features of the sensing material allow the assessment of urinary FPB at relevant clinical levels. In addition, the sensor was selective for FPB compared to the standard biomarker of venous thromboembolism, D-Dimer. The stability of the material was evidenced by the reusability study, which demonstrated reversibility of the maximum intensity after three cycles of recognition and regeneration. Moreover, the sensor showed good performance for the spiked FPB detection in control human urine.Overall, the application of such label-free sensor offers high selectivity and stability, as well as easy operation. It may constitute an alternative method for non-invasive and real-time detection of various protein biomarkers in point-of-care.

Poly(3,4-ethylene dioxythiophene):Poly(styrene sulfonate)-Functionalized Reduced Graphene Oxide Electrode for Ionic Electroactive Polymer Actuators

Ionic electroactive polymer (IEAP) actuators, which offer advantages such as reduced device weight, flexibility, and large deformation under low voltages (1–5 V), have found utility in applications such as biomimetic robots, actuators, and sensors. In this context, in this study, we fabricate poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)-reduced graphene oxide (PEDOT:PSS-rGO) composite paper electrodes for actuator application. PEDOT:PSS-rGO paper electrodes are prepared by vacuum filtration of a PEDOT:PSS-rGO mixture that is subsequently subjected to heat treatment under an argon atmosphere via furnace annealing. We find that a 5:1 weight ratio of PEDOT:PSS-GO provides the lowest sheet resistance. We next fabricate a PEDOT:PSS-rGO actuator via filtration and the hot-pressing method with rGO paper electrodes, which have hydrophobic properties and low liquid permeability that effectively prevents water evaporation, and we examine its actuating performance. Our results indicate that after functionalization with PEDOT:PSS, the electrical properties and surface roughness of PEDOT:PSS-rGO composite paper electrode are improved. Further, the mechanical properties of the IEAP actuator based on the PEDOT:PSS-rGO paper electrodes exhibits enhanced performance by a factor of 4 relative to an actuator with conventional rGO electrodes.