Search

Building an optical filtration function into a microfluidic chip is a promising way of simplifying the optical detection system of a microfluidic device. In this paper, a PDMS microfluidic chip filter that is capable of transmitting chlorophyll fluorescence and blocking interfering light in the visible wavelength range was developed for living algae detection with a smartphone. The chip was fabricated by sealing a layer of crystal violet solution in a PDMS layer on the top of the Sudan II-doped PDMS slab, which has a straight microchannel. Optimum dye concentrations and thicknesses for the crystal violet solution layer and Sudan II-doped PDMS slab were investigated and determined by spectrum measurements. It was found that the cut-on range of this integrated microfluidic chip is extended to about 625 nm and the transmittance in the chlorophyll fluorescence range (650 nm to 710 nm) is as high as 95%, when 25 mg L

In this article we demonstrated a novel interference behavior excited by visible light in the capillary waveguide (CWG). We investigated the sensing principle of CWG with filling liquid and optical characteristics of interference systematically. This CWG-based sensing element is theoretically verified to possess continuously tunable thermal sensitivity by changing the thermo-optic coefficient of the filling liquid. As expected, experimental results show that the proposed sensor possesses sharp interference fringes and the tunable sensitivity of temperature. Unlike most optical fiber interferometers, the optical path difference of our sensing element is generated in the wall of CWG instead of air cavity. Besides, interference occurs in the visible light band, which greatly improves dynamic range and reduces the cost of system setup. The novel optical behavior we investigated offers a way to the utility of the waveguide as an optical interferometer.

Wearable devices such as data gloves have experienced tremendous growth over the past two decades. It is vital to develop flexible sensors with fast response, high sensitivity and high stability for intelligent data gloves. Therefore, a tractable low-cost flexible data glove with self-calibration function based on a space-division multiplexed flexible optical fiber sensor is proposed. A simple, stable and economical method was used to fabricate flexible silicone rubber fiber for a stretchable double-layered coaxial cylinder. The test results show that the fiber is not sensitive to the temperature range of (20~50 °C) and exhibits excellent flexibility and high stability under tensile, bending and torsional deformation. In addition, the signal detection part of the data glove enables compact and efficient real-time information acquisition and processing. Combined with a self-calibration function that can improve the accuracy of data acquisition, the data glove can be self-adaptive according to different hand sizes and bending habits. In a gesture capture test, it can accurately recognize and capture each gesture, and guide the manipulator to make the same action. The low-cost, fast-responding and structurally robust data glove has potential applications in areas such as sign language recognition, telemedicine and human–robot interaction.

A facile hydrothermal method is used to simultaneously introduce S2– and Se2– in Mn–Co precursor to fabricate a novel quaternary metal sulfur selenide electrode. Mn–Co–S–Se electrodes exhibit excel...

A microcapillary-based localized surface plasmon resonance (LSPR) sensor with a large dynamic refractive index (RI) detection range was reported in the present article. Au nanoparticles (NPs) were immobilized onto the inner wall of microcapillary to achieve LSPR sensing. By establishing an energy loss model for evanescent field, we investigate the optical characteristics of Au NPs in microcapillary-based evanescent field and the sensing properties of LSPR sensors systematically. Unlike traditional LSPR sensors, simulated and experimental results demonstrate that these sensors possesses a large dynamic detection range and high tunable-sensitivity due to the extinction efficiency of Au NPs in evanescent field. In addition, the hollow structure of microcapillary can be used as a sensing element as well as a fluid channel. It can reduce the length of sensing region and realize the extraction and detection of trace sample simultaneously, which is very helpful for achieving miniaturization and integration of sensing system. The proposed sensor can achieve a large dynamic RI detection range between 1.328 and 1.470 and offer favorable biosensing property with 3 nm detection limit for human IgG. Being cost-effective, miniaturized and integrated, it is potentially used for environmental monitoring and minimally invasive medical diagnostics.

Heterozygous variants of KCNQ2 can cause KCNQ2 associated neurodevelopmental disorder, mainly are benign (familial) neonatal or infantile epilepsy (B(F)NE or B(F)IE) and developmental epileptic encephalopathy(DEE). Moreover, some intermediate phenotypes, including intellectual disability (ID), and myokymia are related to the gene.We collected a non-syndromic ID male patient with a novel KCNQ2 missense variant. Whole cell electrophysiology, western blotting, and immunofluorescence were adopted to analyze the variant's functional alterations.The patient presented with global developmental delay since his infancy. He still had profound ID but did not have epilepsy at the adolescence. The de novo KCNQ2 variant p.R75C (NM_172107) in the NH2 domain identified here showed a slightly hyperpolarized shift of activation curves and larger current density in homomeric configurations, which could be abolished in co-expression with Kv7.2 or Kv7.3 wild-type. Western blotting and immunocytochemistry supported that the expression of variant p.R75C is lower than the Kv7.2 wild-type. The findings indicated variant p.R75C causes mild gain-of-function (GOF) of Kv7.2 channel.We report a non-syndromic ID patient with a KCNQ2 mild GOF variant, adding evidence for this rare clinical phenotype in the disorder. We propose that individuals with KCNQ2 GOF variants are prone to have cognitive impairments.

The development of data glove is very rapid, and it is widely used in the field of human-robot interaction. Flexible optical fiber sensors are widely used in data gloves. Hereby, a flexible data glove based on space-division multiplexed flexible optical fiber sensor is proposed. The fiber exhibits high optical transmission stability and good sensing performance under deformation. Our data glove accurately recognizes and tracks gestures, and then guide the manipulator to make the same gesture. It is believed that the application of data glove will be more widespread.

Binding behaviors of proteins are important for applications in the field of biochemistry. Though a standard assay has a favorable limit of detection (LOD), it is mainly limited to indirect observation via fluorescence labeling. We reported and demonstrated a novel label-free sensing approach based on a near-infrared (NIR) surface plasmon resonance (SPR) sensing chip modified with a graphene-gold surface architecture in this paper. The NIR excitation wavelength can greatly improve the sensitivity of SPR sensing derived from the wavelength modulation-based methodology. Moreover, benefiting from the excellent electro-optical properties of graphene in NIR range, the graphene-gold surface architecture was built to further improve the sensing sensitivity. Experimental results proved the superiority over most of those reported previously in terms of ultra-sensitivity (39,160 nm/RIU) and resolution (5.107 × 10

Background Autism spectrum disorder (ASD), a neurodevelopmental disorder, is featured by impaired social communication and restricted and repetitive behaviors and interests. ASD and comorbid neurodevelopmental disorders (ASD-NDDs), especially epilepsy and intellectual disability (ID)/global developmental delay (GDD) are frequently presented in genetic disorders. The aim of this study was to explore the clinical and genetic profile of ASD in combination with epilepsy or ID/GDD. Methods We retrospectively analyzed the clinical characteristics, and genetic spectrum of pediatric patients presenting ASD-NDDs with proven genetic etiology. The pathogenicity of variants was conducted by molecular geneticists and clinicians complied with the guidelines of the American College of Medical Genetics and Genomics (ACMG). Results Among 154 patients with ASD-NDDs, 79 (51.3%) patients gained a genetic diagnosis. Most patients (78/79, 98.7%) had comorbid ID or GDD, and 49 (49/79, 62.0%) had comorbid epilepsy. The clinical characteristics of those 79 patients were varied. 87 genetic variants were found among the 79 pedigrees. Most of the involved genes have roles in gene expression regulation (GER) and neuronal communication (NC). Most genes have been proven to be ASD-related genes, and some of them were not reported to contribute to ASD previously. Conclusion We summarized the genetic and clinical profile of 79 ASD-NDDs patients with proven genetic etiology. The genetic spectrum of ASD was expanded, and we highlighted a novel possible ASD candidate gene PRTG.

Background SYN1 encodes synapsin I, which is a neuronal phosphoprotein involving in regulating axonogenesis and synaptogenesis. Variants in the gene have been associated with X-linked neurodevelopmental disorders in recent years. Methods In the study, we reported two male patients with familial SYN1 variants related neurodevelopmental disorders from Asian population. Previously published cases with significant SYN1 variants from the literature were also included to analyze the phenotype and genotype of the disorder. Results Two maternally inherited SYN1 variants, including c.C1076A, p.T359K in proband A and c.C1444T, p. Q482X in proband B (NM_133499) were found, which have never been described in detail. Combining with our research, all reported probands were male in the condition, whose significant SYN1 variants were inherited from their asymptomatic or mild affected mother. Although the disorder encompasses three main clinical presentations: mental deficiency, easily controlled reflex seizure and behavior problems, patients’ clinical manifestations vary in genders and individuals, even in the same pedigree. Conclusion We firstly reported two familial SYN1-related neurodevelopmental disorders in Asian pediatric patients. Gender and phenotype differences should be highly valued in the disorder.

Cardio-facio-cutaneous (CFC) syndrome is an extremely rare autosomal dominant genetic disease due to BRAF and other gene mutations. The main characteristics of the patients are craniofacial deformities, cardiac malformations, skin abnormalities, delay of language and motor development, gastrointestinal dysfunction, intellectual disability, and epilepsy. In this case, the child has a typical CFC syndrome face and developmental delay. The gene results of the second-generation sequencing technology showed that there was a mutation site c.1741AG (p. Asn581Asp) (heterozygous) in exon 14 of the BRAF (NM_004333.5) gene. The mutation was not observed in the child's parents. The above-mentioned mutation may be a de novo mutation. There is no effective therapy for this disease so far.心-面-皮肤(cardio-facio-cutaneous，CFC)综合征是一种极其罕见的常染色体显性遗传病。患者的主要特征为颅面部畸形、心脏畸形、皮肤异常、语言和运动发育迟缓、胃肠道功能障碍、智力障碍及癫痫。本例患儿具有典型的CFC综合征面容以及发育迟滞。二代测序技术结果显示：患儿BRAF(NM_004333.5)基因14号外显子上存在1个突变位点c.1741AG(p. Asn581Asp)(杂合)，其父母均未发现上述变异，该变异可能为新生突变。本病尚没有特效的治疗方法。.

Background It has been reported that de novo heterozygous variants of DEAF1 can cause DEAF1-associated neurodevelopmental disorder. The purpose of this article is to explore the clinical and genetic characteristics of Chinese patients harboring de novo DEAF1 variants. Methods We assembled a cohort of six unrelated patients with de novo variants in DEAF1. Clinical and genetic features of these patients were summarized. Results Each child showed intellectual disability (ID)/ global developmental delay (GDD). Severe language impairment was prominent. Behavior problems, seizures, sleep disturbance, and a high pain threshold were common features. DEAF1-related seizures were reported to be difficult to treat or intractable. Seizures in our cohort were almost all treatable. Valproic acid was the most commonly used drug. Five heterozygous missense mutations of DEAF1 gene were identified, three of which (p.W234C, p.L203P, p.H275Q) were not published in literature before. Conclusion Mutations of DEAF1 gene should be considered in ID/GDD patients with a nonspecific phenotype, comprising intellectual disability, prominent speech delay, abnormal behaviors, especially autism. In our study, DEAF1-related epilepsy is completely treatable in Eastern-Asian individuals when compared to patients in other regions, and valproic acid can be used as a first choice. The knowledge of DEAF1-related neurodevelopmental disorder and the de novo variant database of DEAF1 were expanded.

Background: SYN1 encodes synapsin I, which is a neuronal phosphoprotein in relation to the membranes of small synaptic vesicles. Pathogenic variants in the gene have been confirmed as genetic causes of neurodevelopmental disorders. Methods: In our study, we collected clinical information of two male probands with intellectual disability, and performed whole exome sequencing on both patients and their parents. We also reviewed more SYN1 variant cases in pervious publications.Results: Two maternally inherited variants in SYN1 gene (NM_133499:c.C1076A (p.T359K) in proband A and NM_133499:c.C1444T (p. Q482X) in proband B) were found in our patients, which have never been described in detail before. After a literature review, we found that all probands have been reported so far were male, who inherited the significant SYN1 variants from their asymptomatic or mild affected mother. Although the disease encompasses three main clinical presentations: mental deficiency, easily controlled reflex seizure and behavior problems, the phenotypes of family members vary in gender.Conclusion: Here, we firstly report two familial SYN1-related neurodevelopmental disorders in Asian pediatric patients. Our results supported that gender and phenotype differences should be highly valued in this disorder.

Biomolecular detection at a low concentration is usually the most important criterion for biological measurement and early stage disease diagnosis. In this paper, a highly sensitive nanoplasmonic biosensing approach is demonstrated by achieving near‐infrared plasmonic excitation on a continuous gold‐coated nanotriangular array. Near‐infrared incident light at a small incident angle excites surface plasmon resonance with much higher spectral sensitivity compared with traditional configuration, due to its greater interactive volume and the stronger electric field intensity. By introducing sharp nanotriangular metallic tips, intense localization of plasmonic near‐fields is realized to enhance the molecular perception ability on sensing surface. This approach with an enhanced sensitivity (42103.8 nm per RIU) and a high figure of merit (367.812) achieves a direct assay of ssDNA at nanomolar level, which is a further step in label‐free ultrasensitive sensing technique. Considerable improvement is recorded in the detection limit of ssDNA as 1.2 × 10−18 m based on the coupling effect between nanotriangles and gold nanoparticles. This work combines high bulk‐ and surface‐sensitivities, providing a simple way toward label‐free ultralow‐concentration biomolecular detection., A highly sensitive nanoplasmonic biosensing approach is reported by achieving near‐infrared plasmonic excitation on a continuous gold‐coated nanotriangular array. This sensor possesses an enhanced sensitivity of 42 103.8 nm per RIU and a high figure of merit of 367.812. This technical approach is used to detect single‐stranded DNA hybridization adsorption events by using gold nanoparticles and achieves an estimated detection limit of 1.2 × 10−18 m.

To investigate the effects of ventricular shunt placement in children with post-infective hydrocephalus. Methods: A total of 24 cases of post-infectious hydrocephalus, who received ventricular shunt, were enrolled. Age, gender, disease progression, clinical manifestation, laboratory data, treatment, prognosis, complication, and sequela for each patient were retrospectively reviewed. Results: Of the 24 cases, 8 had a full recovery, 11 had slight sequela, 2 had severe sequela, 1 was in vegetative state, and 2 died because of bacterial meningitis and tubercular meningitis. Epilepsy, mental impairment, visual and hearing damage were the main sequelae. Conclusion: Ventricular shunt is the preferred treatment in children with post-infective hydrocephalus, which shows positive clinical efficacy and can improve the long-term prognosis of such patients.目的：探讨脑室分流术在感染后脑积水患儿中的应用价值。方法：选取行脑室分流术的脑膜炎后脑积水患儿24例。对患儿的临床资料进行回顾性分析，包括性别、起病年龄、病程、临床表现、实验室检查结果、治疗经过、手术方式、并发症及后遗症等。结果：24例患儿，痊愈8例，遗留轻微后遗症11例，严重后遗症2例，植物状态1例，死亡2例(细菌性脑膜炎1例、结核性脑膜炎1例)，后遗症以癫痫、智力损害、视听损害为主。结论：脑室分流术对脑膜炎后脑积水患儿有确切的临床疗效，有助于改善患者远期预后，是治疗感染后脑积水的重要方法。.

We demonstrated a novel self-reference surface plasmon resonance (SPR) fiber biosensor, which provided a multiple-beam interference referencing signal for refractive index (RI) compensating. The sensor was fabricated by splicing a capillary to a multimode fiber (MMF) coated with a gold film. The gilded MMF acts as the measuring channel while the capillary is used as referencing channel. The experiment result showed that the measuring signal has an irreversible change corresponding specific binding and referencing signal has reversible change. It indicated that the measuring signal can inspect biomolecular interactions in real time and the referencing signal can be used to compensate for interference effects due to bulk RI changes. The sensor provides a high sensitivity of 1470.291 nm/RIU and a resolution about $3.536 \times {10}^{\mathrm { {-5}}}$ RIU. In addition, this self-reference SPR biosensor we proposed is low cost, simple, and reproduction, which can be applied in biochemical sensing field.

A highly sensitive localized surface plasmon resonance (LSPR)-based micro-capillary biosensor for micro-measurement was described in this letter. The sensing strategy relies on the interrogation of changes in transmission intensity due to the evanescent field absorption of gold nanoparticles immobilized on the inner wall of micro-capillary. The absorbance due to the LSPR was found to be linear to refractive index changes between 1.328 and 1.3617, and the sensitivity was calculated to be 937%RIU -1 . Then, to evaluate the biosensing performance of the LSPR sensor, we demonstrated the capture of transferrin protein by a layer of anti-transferrin solution immobilized on the LSPR sensor at different concentrations. Experimental results suggest that the biosensor we reported presents a good performance in real-time biochemical detection. In addition, with the advantages of low cost, simplicity, high sensitivity, and less amount of samples required, the biosensor we reported can be used for rapid micro measurement in chemical, biological, and medical applications.

We report a capillary-based surface plasmon resonance sensor that integrates sample collection, injection, and measurement. The sensor reported here can be fabricated at low cost and possesses a small and robust package. The hollow structure of the capillary not only can be used as a fluid channel but also allows light to travel along a spiral and straight line, which is very helpful for reducing the length of the sensing region. The operation wavelength of the sensor can be tuned with a harmless high-index dielectric layer, which makes it possible to generate a reference signal to correct the effect of changes in the bulk refractive index or temperature. Our experiments show that the sensor can operate at room temperature and is capable of performing label-free detection and real-time monitoring through a single sensing device. Furthermore, similar to needles and insertable probes, the sensor could also potentially be used for minimally invasive medical diagnostics and monitoring. As a biosensor, it will be a practical and specific detection device that can be widely used, such as in biological and life sciences research, and rapid diagnostics.

There is an urgent need of label-free technique with low limit of detection (LOD) for biomedical research and early clinical diagnostics. Surface plasmon resonance (SPR) as a label-free approach has been exploited in DNA determination, but the LOD of most SPR sensors is inferior to labeling approaches. A novel approach for SPR biosensing with low LOD was reported in the present study. SPR for long wavelength excitation is theoretically and experimentally demonstrated to possess a high refractive index sensitivity of 11773.93 nm/RIU due to the long decay length of the electromagnetic field near the metal surface, which is optimized by an order of magnitude compared to traditional SPR sensor. Subsequently, self-referencing sensing strategy was employed to eliminate cross-sensitivity problem and further improve sensing accuracy significantly. Finally, we focused on using this sensor to measure DNA hybridization events using graphene oxide-assisted Au nanoparticle conjugates as signal amplification tags. It achieves a large dynamic range of 10−15-10-11 M and a low LOD of 0.2 fM for target DNA determination. The proposed SPR sensing architecture is technologically simple, highly sensitive and extensively appropriate for existing SPR instrumentation, so it has a great potential for low LOD of various biomolecules.

A temperature-compensating fiber-optic surface plasmon resonance (SPR) biosensor based on a Fabry–Perot (FP) interference is described and demonstrated in this letter. The sensing element includes an SPR measuring signal and an FP referencing signal, which appear on gold-coated multimode fiber and capillary, respectively. Because the FP sensing element is sensitive to temperature while insensitive to the refractive index, the referencing channel compensates for the impact of external ambient temperature and enhances the accuracy and reliability of the biosensor. The performance of the temperature-compensating SPR biosensor for accurate measurements is evaluated through the specific binding between Con A and RNase B under interference temperature. In addition, the design and fabrication of the temperature-compensating fiber SPR biosensor are cost effective and simple.

An optical fiber displacement sensor with a large measuring range for simultaneous displacement and temperature measurement is presented in this paper. We developed a specific transducer based on the piston and hydraumatic structure to realize a large displacement measurement, which combined the large measuring range and high precision into a single sensor system. The spectrum showed two reflection peaks used to compensate for cross-sensitivity in the displacement detection. This displacement sensor can linearly work in a large measuring displacement range greater than 45 mm with a high sensitivity of 0.036 nm/mm. The sensor we reported can be developed for real-time displacement monitoring in many industrial environments such as the mechanical shape or liquid level monitoring.

A high-sensitivity and wavelength-tunable temperature sensor based on a short piece of fused-silica microcapillary (FSC) spliced between two single mode fibers (FSCs) and immerged in ethonal solution is proposed and experimentally investigated. Using the thermo-optic effect of ethanol and high sensitivity to refractive index of the FSC modal interference, the temperature sensitivity of the sensor immerged in ethanol solutions is significantly increased over an FSC sensor in air. Besides, the sensitivity and the feature wavelength of the interferometer can be tuned by adjusting the concentration and refractive index of the filling ethonal solution, which is important for achieving the maximum measurement range.

A miniaturization and integration dual-channel fiber optic surface plasmon resonance (SPR) system was proposed and demonstrated in this paper. We used a yellow light-emitting diode (LED, peak wavelength 595 nm) and built-in web camera as a light source and detector, respectively. Except for the detection channel, one of the sensors was used as a reference channel to compensate nonspecific binding and physical absorption. We packaged the LED and surface plasmon resonance (SPR) sensors together, which are flexible enough to be applied to mobile devices as a compact and portable system. Experimental results show that the normalized intensity shift and refractive index (RI) of the sample have a good linear relationship in the RI range from 1.328 to 1.348. We used this sensor to monitor the reversible, specific interaction between lectin concanavalin A (Con A) and glycoprotein ribonuclease B (RNase B), which demonstrate its capabilities of specific identification and biochemical samples concentration detection. This sensor system has potential applications in various fields, such as medical diagnosis, public health, food safety, and environment monitoring.

We introduced a nanopatterned fiber-optic interferometer (FOI) based on an optical fiber line embedded with a short capillary which excites the evanescent field by total reflection of light in the wall waveguide interacting with the fluid and causing the optical signal change. As modal interference was generated with near-infrared light in the tube wall, we detected a reversible wavelength shifts of the proposed FOI in the interference fringe upon water vapor exposure by using an optical fiber interrogator. We also deposited a patterned palladium (Pd) nanoparticle film on the outer surface of the FOI by using self-assembly microspheres as a template and detected the reaction of the Pd membrane with hydrogen through monitoring the wavelength shifts of interference fringes. The Pd nanoparticle restrained the fiber stress response caused by hydrogen-induced expansion of the Pd film, and theoretically helped to improve the evaluation accuracy of the Pd permittivity in hydrogen. In addition, the nanoparticle-coated FOI with asymmetric structure could serve as a Mach-Zehnder interferometer (MZI) for fast hydrogen sensing and air refractive index measurement. Considering sensitivity and detector parameters, the FOI could provide a high resolution up to 7.57 × 10−7 RIU.

Because relative humidity is an important indicator to evaluate the environment quality of production and daily life, humidity sensors have been widely used in various fields. In this work, we proposed a high-sensitivity evanescent field humidity sensor based on micro-capillary and graphene oxide (GO) film. The capillary wall was coated by GO sheets for 1, 3 and 5 cycles, and the interaction between GO and the evanescent field on the capillary wall was experimentally and theoretically investigated. We tested the performance of the sensor with a relative humidity range of 30%RH-70%RH at 25°C. The experimental results show that the sensitivity of the sensor to humidity increases with the compactness of the GO coating. In addition, considering the extinction caused by the GO sheet, the transmission loss and the number of reflections in the capillary wall, the optimal length of the capillary was investigated in order to obtain a good spectral response. Since the cycle of GO coating was controllable, we found that the sensor has a tunable humidity sensitivity. This evanescent field humidity sensor can be applied in all-fiber optic networks for environmental sensing and health monitoring.

A novel self-referencing surface plasmon resonance (SPR) biosensor for detection of transferrin is demonstrated using a micro-capillary as the sensing element. The biosensor employs the SPR mode as a measuring signal and the Fabry-Perot (FP) mode as a referencing signal. The SPR mode is generated in the gold film that is coated on the outside of the capillary; instead, the FP mode is excited in the capillary, which is filled with de-ionized water. The FP mode is sensitive to temperature and insensitive to refractive index, which can be used as a referencing signal to compensate the effects caused by the temperature fluctuation. The sensor provides a high sensitivity of 1783.943 nm/RIU (refractive index unit) and a resolution of about 7.287×10sup-5/sup RIU. The self-referencing biosensor was applied to measurement of transferrin protein. It can monitor the interaction of transferrin protein with anti-transferrin in real time (0-5.228 μM). The simple and low-cost SPR sensor can be used for highly sensitive self-referencing biosensing for further investigations.

In this paper, we propose and demonstrate a novel self-referencing surface plasmon resonance (SPR) fiber-optic sensor which provides a Fabry-Perot (FP) interference referencing signal for temperature compensating. The sensor is fabricated by splicing a capillary partly coated with gold film between multimode fibers. The multimode fibers act as the lead-in and lead-out fibers while the capillary is used as sensing element. Because the FP interference and SPR effects can occur in the capillary simultaneously, the spectrum of the sensor exhibits SPR absorption and FP interference fringes. Due to the FP interference fringe sensitive to temperature while insensitive to refractive index (RI), it can be used as referencing signal and the SPR absorption was used as measuring signal. Experimental results show that this approach we presented can compensate temperature effect and develop this sensor as a practicable high-sensitivity sensing device. Moreover, as a self-referencing fiber-optic SPR sensor, this simple and low-cost element can be used for highly sensitive biosensing for further investigations.

We present a localized surface plasmon resonance fiber optic biosensor based on an intensity interrogation mechanism. A layer of gold nano sphere is deposited on a fiber optic sensor probe which works as the sensing element and is immobilized on the sidewall of an unclad optical fiber via two different immobilization methods (amino silane method and layer by layer self-assembly method). Different self-assembly layers were also respectively investigated by using layer by layer self-assembly method to explore the optimum layer number. Experimental results reveal that PDDA/PSS/PAH layer self-assembly method provides the best LSPR response. We obtain a refractive index sensitivity as 6.57RIU-1 in a RI range of 1.3266~1.3730. We also conduct real-time and label free monitoring of Ribonuclease B/Con A biomolecular interaction by using this sensor prototype and demonstrate it can perform qualitative and quantitative detection in real-time biomolecular sensing.

We proposed and demonstrated a micro-capillary-based, high-sensitivity evanescent field biosensor for the cost-effective, rapid, and sensitive analysis and detection of specific DNA sequences. By functionalizing the surface of the tubing wall with ssDNA probe sequences, label-free DNA detection is achieved. The wavelength shift response of the surface-functionalized biosensors to DNA hybridization is monitored in real time. Our experiments show that the biosensor can operate at room temperature and is capable of performing label-free hybridization detection, analyte concentration measurement and nucleotide mismatch detection through a single sensing device. The sensor has many advantages, such as a simple manufacturing process, standardized production control, reliable quality, low cost and an economic demodulator. The compact nature and miniature size of the biosensing detection system makes it a good candidate for the rapid and highly sensitive detection of low-concentration analytes in micro-samples for cost-effective, real-time, and on-site analysis in the fields of life science, pharmaceutical chemistry, medical science and criminal investigation.

We demonstrate a fiber optic surface plasmon resonance (SPR) biosensor based on smart phone platforms. The light-weight optical components and sensing element are connected by optical fibers on a phone case. This SPR adaptor can be conveniently installed or removed from smart phones. The measurement, control and reference channels are illuminated by the light entering the lead-in fibers from the phone’s LED flash, while the light from the end faces of the lead-out fibers is detected by the phone’s camera. The SPR-sensing element is fabricated by a light-guiding silica capillary that is stripped off its cladding and coated with 50-nm gold film. Utilizing a smart application to extract the light intensity information from the camera images, the light intensities of each channel are recorded every 0.5 s with refractive index (RI) changes. The performance of the smart phone-based SPR platform for accurate and repeatable measurements was evaluated by detecting different concentrations of antibody binding to a functionalized sensing element and the experiment results were validated through contrast experiments with a commercial SPR instrument. This cost-effective and portable SPR biosensor based on smart phones has many applications, such as medicine, health and environmental monitoring.

We demonstrated a simple method for self-reference and label free biosensing based on a capillary sensing element and common optoelectronic devices. The capillary sensing element is illuminated by a light-emitting diode (LED) light source and detected by a webcam. Part of gold film that deposited on the tubing wall is functionalized to carry on the biological information in the excited SPR modes. The end face of the capillary was monitored and separate regions of interest (ROIs) were selected as the measurement channel and the reference channel. In the ROIs, the biological information can be accurately extracted from the image by simple image processing. Moreover, temperature fluctuation, bulk RI fluctuation, light source fluctuation and other factors can be effectively compensated during detection. Our biosensing device has a sensitivity of 1145%/RIU and a resolution better than 5.287 × 10-4 RIU, considering a 0.79% noise level. We apply it for concanavalin A (Con A) biological measurement, which has an approximately linear response to the specific analyte concentration. This simple method provides a new approach for multichannel SPR sensing and reference-compensated calibration of SPR signal for label-free detection.

A novel evanescent field refractometer based on a two-core photonic crystal fiber (TWPCF) sandwiched between multimode fibers(MMFs) is demonstrated. Through splicing a short piece of TWPCF between two MMFs, a simple structure and high sensitivity RI sensor can be constructed. Instead of using wavelength information as sensor signal, we focus more on the light intensity signal different from most PCF based RI sensor. The TWPCF section functions as a tailorable bridge between the excited high order modes and the surrounding refractive index (SRI). With a light filter inserting in the front of white light, the transmission spectrum of the light through the sensing region occurs in a welldefined wavelength bands. As a result, the peak power of the transmission light is tailored with the SRI perturbation via the MMF-TWPCF–MMF structure. The experiment result shows a quadratic relation between the light intensity and samples within RI range of 1.33-1.41 while a linear response can be achieved from the 1.33-1.35 which is a most used RI range for biologically sensing.

We present a wavelength-tunable tapered optics fiber surface Plasmon resonance (SPR) sensor by polishing the end faces of multimode fibers(MMF).Two hard plastic clad optical fibers joint closely and are used as the light input and output channels. Their end faces are polished to produce two oblique planes, which are coated with gold film to be the sensing surface and the front mirror. The presence of the tapered geometry formed by the two oblique planes in the orthogonal directions makes it possible to adjust incident angle through changing the tilt angles of the two end faces, so as to achieve tuning the SPR coupling wavelength-angle pair. Compared with previous researches based a tapered optic fiber probe, we report the approach theoretically increase the signal noise ratio (SNR) by separating incident and emergent light propagating in the different coordinate fiber. Since fabricating the sensing surface and the front mirror on the two fibers to replace one single fiber tip, there is more incident light can reach the sensing surface and satisfy SPR effective. In addition, this improvement in structure has advantages of large grinding and sensing area, which can lead to high sensitivity and simple manufacture process of the sensor. Experimental measurement demonstrates the sensor has a favorable SPR resonanceabsorption and the ability of measuring refractive index (RI) of aqueous solution. This novel tapered SPR sensor has the potential to be applied to the biological sensing field.