Polymer-based Sensor Research Articles

Electrochemically Deposited Molecularly Imprinted Polymer-Based Sensors.

This review is dedicated to the development of molecularly imprinted polymers (MIPs) and the application of MIPs in sensor design. MIP-based biological recognition parts can replace receptors or antibodies, which are rather expensive. Conducting polymers show unique properties that are applicable in sensor design. Therefore, MIP-based conducting polymers, including polypyrrole, polythiophene, poly(3,4-ethylenedioxythiophene), polyaniline and ortho-phenylenediamine are frequently applied in sensor design. Some other materials that can be molecularly imprinted are also overviewed in this review. Among many imprintable materials conducting polymer, polypyrrole is one of the most suitable for molecular imprinting of various targets ranging from small organics up to rather large proteins. Some attention in this review is dedicated to overview methods applied to design MIP-based sensing structures. Some attention is dedicated to the physicochemical methods applied for the transduction of analytical signals. Expected new trends and horizons in the application of MIP-based structures are also discussed.

Molecularly imprinted polymer-based electrochemical impedimetric sensors on screen-printed carbon electrodes for the detection of trace cytokine IL-1β

In this study, protein-imprinted sensors were electrochemically fabricated on screen-printed carbon electrodes (SPCEs) for the cytokine interleukin-1β (IL-1β) detection. A double layer comprising poly(o-phenylenediamine) and poly(chromotrope 2R) with a template (i.e., IL-1β biomacromolecules) was formed through the cyclic voltammetry (CV) technique to modify the molecularly imprinted polymer (MIP) films on the SPCEs. The electrochemical sensing properties were investigated via CV and electrochemical impedance spectroscopy to confirm the imprinting effect on the MIP films. The results show that the MIP sensor has a highly sensitive response in the trace IL-1β solution (a few pg/mL) with a limit of detection of 0.23 pg/mL and a limit of quantification of 0.78 pg/mL. Furthermore, the MIP sensor showed high selectivity for IL-1β adsorption compared to other proteins. In summary, based on binary double layers, the impedance sensing platforms of electropolymerized MIP films show potential application in the practical detection of macromolecular proteins.

Microchannel tube NH3 sensor based on metal-organic framework UiO-66 modified polyaniline

Despite the remarkable development in conductive polymer-based NH3 sensors, there are still several obstacles such as long response/recovery time and difficulty in detecting low concentrations of NH3. In this work, polyaniline (PANI) was modified using a metal-organic framework (MOF) UiO-66 to construct a microchannel tube NH3 sensor. Scanning Electron Microscope (SEM) and Brunauer-Emmett-Teller (BET) characterizations disclose that the addition of UiO-66 could induce formation of a highly porous nanofiber PANI film. The sensor can realize the gas response up to 2540% for 100 ppm NH3, and 20% response to 10 ppb NH3 with excellent reversibility and response/recovery time (25 s/14 s). The improved sensing performance is ascribed to the high specific surface area of the PANI/UiO-66 film. Furthermore, the sensor has a microchannel tube structure which can realize fast and effective on-time detection of small-volume NH3 gas. The as-fabricated sensor could be a potential candidate in practical medical monitoring applications.

A Novel Motion Recognition Method Based on Force Myography of Dynamic Muscle Contractions.

Surface electromyogram-based pattern recognition (sEMG-PR) has been considered as the most promising method to control multifunctional prostheses for decades. However, the commercial applications of sEMG-PR in prosthetic control is still limited due to the ambient noise and impedance variation between electrodes and skin surface. In order to reduce these issues, a force-myography-based pattern recognition method was proposed. In this method, a type of polymer-based flexible film sensors, the piezoelectrets, were used to record the rate of stress change (RSC) signals on the muscle surface of eight able-bodied subjects for six hand motions. Thirteen time domain features and four classification algorithms of linear discriminant analysis (LDA), K-nearest neighbor (KNN), artificial neural network (ANN), and support vector machine (SVM) were adopted to decode the RSC signals of different motion classes. In addition, the optimal feature set, classifier, and analysis window length were investigated systematically. Results showed that the average classification accuracy was 95.5 ± 2.2% by using the feature combination of root mean square (RMS) and waveform length (WL) for the classifier of KNN, and the analysis window length of 300 ms was found to obtain the best classification performance. Moreover, the robustness of the proposed method was investigated, and the classification accuracies were observed above 90% even when the white noise ratio increased to 50%. The work of this study demonstrated the effectiveness of RSC-based pattern recognition method for motion classification, and it would provide an alternative approach for the control of multifunctional prostheses.

Ultra-sensitive nano- molecular imprinting polymer-based electrochemical sensor for Follicle-Stimulating Hormone (FSH) detection

A novel nano-molecular imprinting polymer-based electrochemical sensor for follicle-stimulating hormone (FSH) in polycystic ovary syndrome (PCOS) has been developed. The present methods available for PCOS detection are associated with several disadvantages such as they are costly, time-consuming process, and low sensitivity. This proposed biosensor can help to overcome these conditions while providing a dynamic detection range, a lower limit of detection, higher sensitivity, rapid detection, and low-cost detection. As this biosensor is based on the molecular imprinting approach it is highly specific and stable at a higher temperature. To our knowledge, no such biosensor is developed for the diagnosis of PCOS. Highly selective and specific recognition of the follicle-stimulating hormone-molecular imprinting polymer (FSH-MIP) film onto the nanomaterial (NiCo2O4/rGO) modified indium tin oxide (ITO) electrode was done by electropolymerization method. Characterization and behavior of the electrode surface fabricated were investigated by using various surface and electrochemical measurements. Under optimal conditions, the detection limit and linear working range obtained were 0.1 pM and 0.1 pM to 1 µM, respectively. This fabricated biosensor is simple, rapid, and sensitive for the electrochemical detection of FSH based on the MIP technique.

Secondary embossing method for the capsulation of high-sensitive flexible piezoresistive sensors

Due to the mismatch between thermal expansion and hygroscopic expansion coefficients of polymer packaging materials, the stress and reliability of packaging structure present significant influences on the performance of flexible sensors. In this work, a new capsulation method for polymer-based flexible piezoresistive sensing systems was proposed based on differential-temperature hot embossing. The capsulate mold of the flexible sensing system is designed and the flexible sensor is packaged into a polydimethylsiloxane (PDMS) film to form a “sandwich” structure. The influences of the first embossing pressure and the second embossing time on capsulation result were investigated systematically. The results showed that the optimal parameters for the first embossing pressure and second embossing time were 1.4 MPa and 180 s, respectively. The interlayer peel force of obtained samples under this condition could reach a maximum of 5.7 N. This PDMS bulk bonding method can improve the cracking problem of the sample and provide more effective protection for the flexible sensors, compared with the traditional capsulation methods, this packaging method has little effect on sensor sensitivity (decreased by 0.64 kPa−1). After the packaging is completed, the polymer-based flexible piezoresistive sensor presents a high sensitivity (−5.64 kPa−1), and at the same time, a fast response (92 ms).

An Ultra-Sensitive Molecularly Imprinted Poly(Aniline) Based Electrochemical Sensor for the Determination of Bisphenol A in Synthetic Human Serum Specimen and Plastic Bottled Water Samples

We explain the development of an ultra-sensitive molecularly imprinted polymer-based electrochemical sensor for rapid and selective determination of bisphenol A (BPA) in human serum and water samples. Electropolymerization of functional monomer aniline was performed in the presence of BPA by cyclic voltammetry (CV) to prepare a molecularly imprinted poly(aniline) based GCE sensor (MIP(ANI)/GCE). The developed MIP surface was characterized using Fourier-transform infrared spectroscopy, Raman spectrometry, scanning electron microscopy, contact angle measurements, CV, and electrochemical impedance spectroscopy. The MIP(ANI)/GCE sensor showed a highly sensitive performance with a linear range of 1.0 and 8.0 × 10−15 M. The limit of detection (LOD) and limit of quantification (LOQ) values were 0.193 and 0.643 fM, respectively. The applicability of the MIP(ANI)/GCE was assessed by applying it to human serum and plastic bottled water samples. The LOD and LOQ values were calculated as 0.257 and 0.856 fM for the serum sample. Imprinting factor and interference studies were also carried out using similarly structured compounds and the most common interfering agents showing the selectivity of the MIP(ANI)/GCE sensor. Finally, the non-imprinted polymer (NIP)-based sensor was prepared to control the MIP(ANI)/GCE performance.

Uncertainty Analysis of Polymer-Based Capacitive Relative Humidity Sensor at Negative Temperatures and Low Humidity Levels

Uncertainty Analysis of Polymer-Based Capacitive Relative Humidity Sensor at Negative Temperatures and Low Humidity Levels

Novel polymer-based thermoresponsive photonic crystal sensors with broad wavelength shifts

Novel broad wavelength-shifted thermoresponsive sensors were fabricated by introducing ferrocene groups into polymeric photonic crystals.

Facile fabrication and luminescence properties of a new ZnII coordination polymer-based fluorescent sensor toward antibiotics

A new ZnII-based coordination polymer could selectively and sensitively recognize NFT and DCN via turn-off effect. Interestingly, a mixed matrix film for visualizable sensing has been successfully developed.

Selective Detection of Penicillin G Antibiotic in Milk by Molecularly Imprinted Polymer-Based Plasmonic SPR Sensor.

Molecularly imprinted polymer-based surface plasmon resonance sensor prepared using silver nanoparticles was designed for the selective recognition of Penicillin G (PEN-G) antibiotic from both aqueous solution and milk sample. PEN-G imprinted sensors (NpMIPs) SPR sensor was fabricated using poly (2-hydroxyethyl methacrylate-N-methacroyl-(L)-cysteine methyl ester)-silver nanoparticles-N-methacryloyl-L-phenylalanine methyl ester polymer by embedding silver nanoparticles (AgNPs) into the polymeric film structure. In addition, a non-imprinted (NpNIPs) SPR sensor was prepared by utilizing the same polymerization recipe without addition of the PEN-G template molecule to evaluate the imprinting effect. FTIR-ATR spectrophotometer, ellipsometer, contact angle measurements were used for the characterization of NpMIPs SPR sensors. The linear concentration range of 0.01–10 ng/mL PEN-G was studied for kinetic analyses. The augmenting effect of AgNPs used to increase the surface plasmon resonance signal response was examined using polymer-based PEN-G imprinted (MIPs) sensor without the addition of AgNPs. The antibiotic amount present in milk chosen as a real sample was measured by spiking PEN-G into the milk. According to the Scatchard, Langmuir, Freundlich and Langmuir–Freundlich adsorption models, the interaction mechanism was estimated to be compatible with the Langmuir model.

Conducting polymer-based sensors for food and drug analysis.

Conducting polymers (CPs) are a category of polymeric materials with conjugated main chains. The characteristic electrical and optical properties of CPs can be fine-tuned through controlling the doping states of CPs. Because of their long-term stability in water, CPs have been demonstrated as electroactive biointerfaces and electrode materials especially in aqueous environments. Serving as multifunctional interfaces and organic electrodes for the integration bioelectronics and devices, CPs have been studied and applied in various biological applications. This paper provides a review of conducting polymer-based electrochemical sensors, particularly those used in biological fields. General conducting polymers and derivatives and their main electrochemical sensing platforms with different design of devices are introduced. Cyclic voltammetry, differential pulse voltammetry, chronoamperometry, electrochemical impedance spectroscopy, and quartz crystal microbalance methods and their features are then explored as detection methods for the analysis of drugs and food. To enhance the sensitivity and lower the detection limit of sensing platforms, various CP-based nanocomposites have been designed and developed. Although the electrodes made of CP-based nanocomposites usually outperform those made of pristine CPs, more systematic studies are required to provide insights into the design of nanocomposite-based electrodes. More applications of CP-based sensors for advanced food and drug analyses are expected.

Micromachined Tactile Sensor Array for RTSA.

This work presents a polymer-based tactile capacitive sensor capable of measuring joint reaction forces of reverse total shoulder arthroplasty (RTSA). The capacitive sensor contains a polydimethylsiloxane (PDMS) dielectric layer with an array of electrodes. The sensor was designed in such a way that four components of glenohumeral contact forces can be quantified to help ensure proper soft tissue tensioning during the procedure. Fabricated using soft lithography, the sensor has a loading time of approximately 400 ms when a 14.13 kPa load is applied and has a sensitivity of 1.24 × 10−3 pF/kPa at a load of 1649 kPa. A replica RTSA prothesis was 3D printed, and the sensor was mounted inside the humeral cap. Four static right shoulder positions were tested, and the results provided an intuitive graphical description of the pressure distribution across four quadrants of the glenohumeral joint contact surface. It may help clinicians choose a right implant size and offset that best fit a patient’s anatomy and reduce postoperative biomechanical complications such as dislocation and stress fracture of the scapula.

Molecularly imprinted polymer-based chemiresistive sensor for detection of nonanal as a cancer related biomarker

Volatile organic compounds are valuable biomarkers for monitoring the metabolic status of cells and even diagnosing diseases, like cancer. Herein, a chemiresistive sensor was developed to detect gaseous nonanal which is one of the biomarkers associated with cancers. Molecularly imprinted polymers (MIPs) and organic solvent-synthesized gold nanoparticles (AuNPs) were combined with a simple process to form a conductive composite as the active layer, which was then drop-casted on the surface of the interdigitated electrodes (IDEs). The conductivity changes that occurred in the presence of the target analyte were measured using a highly accurate potentiostat in a two electrode system. The limit of detection (LOD) and linear range of the sensor were determined as 4.5 ppm and 2.5–100 ppm, respectively. Sensor selectivity was assessed and the analytes were successfully classified using partial least squares discriminant analysis (PLS-DA). The sensor operates at room temperature and is able to detect nonanal in the head space of human plasma in real time mode without the need for pre-concentration.

Dual-Mode Polymer-Based Temperature Sensor by Dedoping of Electrochemically Doped, Conjugated Polymer Thin Films

Polymer temperature sensors are important for applications in food packaging, air conditioning, wearable devices, and biomedicine. However, the sensing range of these sensors is narrow, and the mod...

Highly Elastic and Fatigue-Resistant Graphene-Wrapped Lamellar Wood Sponges for High-Performance Piezoresistive Sensors

Three-dimensional (3D) conductive aerogels with structural robustness and mechanical resilience are highly attractive for sensitive and stable pressure sensing. However, the fabrication of such 3D aerogels often relies on complicated bottom-up assembly processes that involve costly raw materials or intensive energy consumption or directly coating synthetic polymer sponges (e.g., polyurethane) with conductive materials, which may pose environmental concerns for their disposal. Herein, a simple and sustainable strategy is proposed to fabricate a reduced graphene oxide-coated wood sponge (RGO@WS) with a lamellar structure for high-performance piezoresistive sensors. The introduced RGO nanosheets endow the RGO@WS not only with high conductivity but also with high elasticity and excellent fatigue resistance. These features make it an ideal piezoresistive sensor with a high sensitivity of 0.32 kPa–1 (superior to most polymeric sponge-based sensors), high working stability over 10 000 cycles, and excellent sensing reproducibility at ultralow temperatures. Thanks to its prominent sensing performance, the RGO@WS-based sensor can serve as a wearable device for detecting human motions and physiological signals and allows for spatially resolved pressure mapping via integrating the sensors into a large-area sensing array. The developed highly elastic and fatigue-resistant RGO@WS represents a promising and sustainable alternative to the synthetic polymer-based piezoresistive sensors.

Molecularly imprinted polymer-based sensors for cancer biomarker detection

Ultrasensitive, quick, and non-invasive recognition of biomarkers is very useful for detection, screening, and management of cancer effectively. In this regard, there have been enormous number of articles published each year comprising natural biomolecules e.g., antibodies, enzymes, receptors and aptamers as a recognition element of sensors for the detection of cancer biomarkers. However, due to stability issue and high-cost of natural biomolecules, polymeric material-based recognition element involving molecular imprinting has drawn a huge attention over the last couple of decades. The molecularly imprinted polymers (MIPs), also known as “artificial antibodies”, show sensitivity comparable to natural receptors. This review aims to deliver an insight and potential application of the MIPs towards cancer biomarker detection methods. Some discussion about classical recognition elements is also included here for better understanding the biomimicking approach. Many industries have already proved the potential of the new alterative sensing platform and if some of the drawbacks can be addressed carefully during the synthesis of the MIPs, we hope to see MIP-based diagnostic kits for cancer detection. The review is aimed to help the readers and the researchers to understand the potential of MIPs in cancer biomarker detection as well as recognition element for sensors.

An ultrasensitive molecularly imprinted polymer-based electrochemical sensor for the determination of SARS-CoV-2-RBD by using macroporous gold screen-printed electrode

Herein, a novel molecularly imprinted polymer (MIP) based electrochemical sensor for the determination of the receptor-binding domain of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2-RBD) has been developed. For this purpose, first, a macroporous gold screen-printed electrode (MP-Au-SPE) has been fabricated. The MIP was then synthesized on the surface of the MP-Au-SPE through the electro-polymerization of ortho-phenylenediamine in the presence of SARS-CoV-2-RBD molecules as matrix polymer, and template molecules, respectively. During the fabrication process, the SARS-CoV-2-RBD molecules were embedded in the polymer matrix. Subsequently, the template molecules were removed from the electrode by using alkaline ethanol. The template molecules removal was studied using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), and attenuated total reflectance spectroscopy (ATR). The fabricated MIP film acted as an artificial recognition element for the measurement of SARS-CoV-2-RBD. The EIS technique was used for the measurement of the SARS-CoV-2-RBD in the saliva solution. The electron transfer resistance (Ret) of the MIP-based sensor in a ferri/ferrocyanide solution increased as the SARS-CoV-2-RBD concentration increased due to the occupation of the imprinted cavities by the SARS-CoV-2-RBD. The MIP-based sensor exhibited a good response to the SARS-CoV-2-RBD in the concentration range between 2.0 and 40.0 pg mL-1 with a limit of detection of 0.7 pg mL-1. The obtained results showed that the fabricated MIP sensor has high selectivity sensitivity, and stability.

A direct relationship between the sensitivity of the sensors and the intensity of IR CO2 peak in in situ FTIR-LCR meter chemi-impedance SnO2–carbon nanoparticles polymer-based sensors in the detection of organic compounds vapor

Three sensors were prepared with SnO2, carbon nanoparticles (CNPs), and cellulose acetate (CA) composites, and each sensor containing different amounts of SnO2 powder were prepared for the detection of n-dodecane, 2-hexanone, and 3-methylcyclopentanone vapor at room temperature. Sensors with a combination of CNP:CA, SnO2:CA, SnO2:CNPs, and SnO2 composites were used as control, and their performance was compared with that of the sensor based on SnO2:CNPs:CA toward a wide range of 2-hexanone and 3-methylcyclopentanone vapor concentrations. Sensors based on CNPs:CA and SnO2:CNPs:CA selectively responded very well to 3-methylcyclopentanone and 2-hexanone, respectively. The in situ FTIR study revealed that both sensors undergo a deep oxidation process during sensing and the sensitivity of the sensors directly relates to the IR intensity of the CO2 peak at 668 cm−1, and for highly sensitive sensors, the CO2 peak at 668 cm−1 is found to be very intense. The gradient area under the curve of the IR CO2 band at 668 cm−1 against time for more sensitive sensors toward the analyte is larger than that for less sensitive ones. The effect of the amount of SnO2 in the composites indicated that the sensors based on three sensing materials combined at a mass ratio of 1:1:3 were highly selective toward 3-methylcyclopentanone and less selective toward the other two analytes. Sensors based on the composition of SnO2:CNPs:CA at a mass ratio of 1.5:1:3 and those based on the composition of SnO2:CNPs:CA at a mass ratio of 2:1:3 were selective toward 2-hexanone and n-dodecane, respectively. All the fabricated sensors were found to have their sensing ability regenerated after the analytes were removed from the system without losing their sensing and recovery abilities.

Effects of electroactive group and enzyme crosslinkers numbers on analytical performance for conductive polymer-based sensor platforms

This manuscript describes an amperometric sensor application of a new class of triazine-centered monomers functionalized with different numbers of carbazole and hydrazine. In the sensor system, carbazole and hydrazine are designed as transducer and enzyme crosslinker groups, respectively. The monomers (TECA and CTDA) containing different numbers of carbazole and hydrazine were electrochemically polymerized on a graphite (GR) electrode. A new sensor platforms for glucose determination have been obtained by immobilizing glucose oxidase (GOx) on the polymer film surfaces. The pTECA/GOx and pCTDA/GOx-based electrodes were investigated for an evaluation of electron transfer between the enzyme and electrode at bioelectrochemically relevant potentials via pTECA and pCTDA layer. The results show that amperometric response values were greater for the polymer containing more hydrazine ends than the polymer containing more carbazole groups. This is due to the that as the hydrazine ends increased, the more enzyme crosslinker groups at the same surface size. The evaluation of two different configurations (pTECA/GOx and pCTDA/GOx) of working electrodes suggested that the pTECA/GOx configuration, which was composed of more hydrazine ends and enzyme, is the more suitable candidate for biosensor applications. Moreover, it was determined that the pTECA/GOx and pCTDA/GOx-based electrodes are reliable for the establishment of advanced electron transfer between enzyme and electrode for the application in amperometric biosensors because of the observed high amperometric response values, and low LOD values.