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papers from the latest issue:
A nanostructured SAW chip-based biosensor detecting cancer cells
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Patrick Bröker, Klaus Lücke, Markus Perpeet, Thomas M.A. Gronewold
A nanostructured chip surface was fabricated enabling binding via spaced antibodies specifically targeting surface proteins of cancer cells and detection of extremely low numbers of circulating tumor cells (CTC) without labeling using a sam® 5 biosensor. The antibody surfaces mostly were generated by self assembly of antibodies to gold nanospots on the sensitive SiO2-surface of a sam® 5 chip. Compared with a complete gold surface, only 40% of the amount of antibodies was bound to the nanospot surface, but structured such that 15-fold higher sensitivity to vital cancer cells was achieved. Human cancer cell lines JEG-3 (lymphoblastic leukemia) and MOLT-17 (placental choriocarcinoma) from cell cultures were successfully detected. The sensor showed significant responses on less than 10 cells injected in a single run. The extreme increase in sensitivity and its simple regeneration emphasizes the usefulness of its introduction in biomedical applications.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Patrick Bröker, Klaus Lücke, Markus Perpeet, Thomas M.A. Gronewold
A nanostructured chip surface was fabricated enabling binding via spaced antibodies specifically targeting surface proteins of cancer cells and detection of extremely low numbers of circulating tumor cells (CTC) without labeling using a sam® 5 biosensor. The antibody surfaces mostly were generated by self assembly of antibodies to gold nanospots on the sensitive SiO2-surface of a sam® 5 chip. Compared with a complete gold surface, only 40% of the amount of antibodies was bound to the nanospot surface, but structured such that 15-fold higher sensitivity to vital cancer cells was achieved. Human cancer cell lines JEG-3 (lymphoblastic leukemia) and MOLT-17 (placental choriocarcinoma) from cell cultures were successfully detected. The sensor showed significant responses on less than 10 cells injected in a single run. The extreme increase in sensitivity and its simple regeneration emphasizes the usefulness of its introduction in biomedical applications.
A novel surface acoustic wave-impedance humidity sensor based on the composite of polyaniline and poly(vinyl alcohol) with a capability of detecting low humidity
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Yang Li, Chao Deng, Mujie Yang
This paper presents a novel humidity sensor composed of a 433MHz surface acoustic wave (SAW) resonator and an interdigitated gold electrode connected in series. The gold electrode was covered with a sensitive film of a composite of processable conductive polyaniline and polyvinyl alcohol. The frequency response of the novel SAW-impedance humidity sensor toward relative humidity (RH) was investigated at room temperature. The sensitivity of the SAW-impedance humidity sensors increased with the increase in the conductivity of the sensitive film. The sensor showed a sensitivity of ∼7.4kHz/%RH at 30%RH, which was increased to 60kHz/%RH at 47%RH. Moreover, such sensors exhibited short response and recovery times and good repeatability. It is worth noting that the sensor showed a linear frequency response to humidity over the range of 0.4–20%RH with a good sensitivity of ∼2kHz/%RH, which reveals its potentials for detecting low humidity.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Yang Li, Chao Deng, Mujie Yang
This paper presents a novel humidity sensor composed of a 433MHz surface acoustic wave (SAW) resonator and an interdigitated gold electrode connected in series. The gold electrode was covered with a sensitive film of a composite of processable conductive polyaniline and polyvinyl alcohol. The frequency response of the novel SAW-impedance humidity sensor toward relative humidity (RH) was investigated at room temperature. The sensitivity of the SAW-impedance humidity sensors increased with the increase in the conductivity of the sensitive film. The sensor showed a sensitivity of ∼7.4kHz/%RH at 30%RH, which was increased to 60kHz/%RH at 47%RH. Moreover, such sensors exhibited short response and recovery times and good repeatability. It is worth noting that the sensor showed a linear frequency response to humidity over the range of 0.4–20%RH with a good sensitivity of ∼2kHz/%RH, which reveals its potentials for detecting low humidity.
Comparison of gas sensor performance of SnO2 nano-structures on microhotplate platforms
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Mark A. Andio, Paul N. Browning, Patricia A. Morris, Sheikh A. Akbar
Metal oxide nano-structures on microhotplate platforms have attracted a great deal of interest in gas sensor research for their potential to create both highly responsive and extremely portable gas sensors. Much of the current research on these sensors has focused upon the creation of hierarchical nanostructures, as van der Waals attraction between nanoparticles leads to agglomeration that impair sensor performance. In this research article, ink-jet printing onto microhotplates was explored as a method of avoiding nanoparticle agglomeration to produce an open film microstructure. Scanning electron microscopy was used to study the deposited thin nanoparticle film featuring an open microstructure free of large agglomeration. Sensor response and response times of ink-jet printed SnO2 nanoparticles were found to be comparable to hierarchical particle films when exposed to methane and carbon monoxide in a background of dry air. Both the SnO2 nanoparticles and microspheres had superior response compared to SnO2 micron-size particles due to increased surface area of the nano-structures. This implies that proper control of the microstructure of the SnO2 nanoparticle films produces similar gas sensor performance to SnO2 hierarchical structures and has the potential for use in reproducibly manufacturing high-performance gas sensors.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Mark A. Andio, Paul N. Browning, Patricia A. Morris, Sheikh A. Akbar
Metal oxide nano-structures on microhotplate platforms have attracted a great deal of interest in gas sensor research for their potential to create both highly responsive and extremely portable gas sensors. Much of the current research on these sensors has focused upon the creation of hierarchical nanostructures, as van der Waals attraction between nanoparticles leads to agglomeration that impair sensor performance. In this research article, ink-jet printing onto microhotplates was explored as a method of avoiding nanoparticle agglomeration to produce an open film microstructure. Scanning electron microscopy was used to study the deposited thin nanoparticle film featuring an open microstructure free of large agglomeration. Sensor response and response times of ink-jet printed SnO2 nanoparticles were found to be comparable to hierarchical particle films when exposed to methane and carbon monoxide in a background of dry air. Both the SnO2 nanoparticles and microspheres had superior response compared to SnO2 micron-size particles due to increased surface area of the nano-structures. This implies that proper control of the microstructure of the SnO2 nanoparticle films produces similar gas sensor performance to SnO2 hierarchical structures and has the potential for use in reproducibly manufacturing high-performance gas sensors.
On the hydrogen sensing characteristics of a Pd/AlGaN/GaN heterostructure field-effect transistor (HFET)
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Chi-Shiang Hsu, Huey-Ing Chen, Chung-Fu Chang, Tai-You Chen, Chien-Chang Huang, Po-Cheng Chou, Wen-Chau Liu
The interesting temperature-dependent hydrogen sensing characteristics of a Pd/AlGaN/GaN heterostructure field-effect transistor (HFET) are studied and demonstrated. Remarkable hydrogen sensing performance is found at a very low concentration of hydrogen gases (≤1ppm H2/air). In addition, a good transistor switching behavior with the high drain current on/off value of 93,680 is obtained for 1% ppm H2/air gas at 523K. The fast transient response as comparable with a Schottky-type hydrogen sensor is also observed. Based on these advantages, the studied device shows a promise for high-performance, high-temperature electronics, and micro electro-mechanical system (MEMS) applications.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Chi-Shiang Hsu, Huey-Ing Chen, Chung-Fu Chang, Tai-You Chen, Chien-Chang Huang, Po-Cheng Chou, Wen-Chau Liu
The interesting temperature-dependent hydrogen sensing characteristics of a Pd/AlGaN/GaN heterostructure field-effect transistor (HFET) are studied and demonstrated. Remarkable hydrogen sensing performance is found at a very low concentration of hydrogen gases (≤1ppm H2/air). In addition, a good transistor switching behavior with the high drain current on/off value of 93,680 is obtained for 1% ppm H2/air gas at 523K. The fast transient response as comparable with a Schottky-type hydrogen sensor is also observed. Based on these advantages, the studied device shows a promise for high-performance, high-temperature electronics, and micro electro-mechanical system (MEMS) applications.
Sensitive detection of indoor air contaminants using a novel gas sensor based on coral-shaped tin dioxide nanostructures
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Yuteng Wan, Huihua Li, Jinyun Liu, Fanli Meng, Zhen Jin, Lingtao Kong, Jinhuai Liu
In order to sensitively detect indoor air contaminants including benzene, formaldehyde, toluene, and acetone, an effective method using a gas sensor based on coral-shaped tin dioxide nanostructures is reported. It is found that the presented gas sensor exhibits obviously enhanced sensing performance toward indoor air contaminants compared with the ones based on some conventional nanostructures, like nanospheres and nanoparticle-based thin film. The mechanism for such fascinating improvement is demonstrated from the nanoscale size-dependent effect by following theoretical models. Our findings not only provide a promising environmental sensor for sensitively detecting indoor air contaminants, but also suggest a general strategy for utilizing the nanoscale effects of nanoparticles in other environmental and energy-related applications, like waste-water absorbents, catalysts, and solar cells.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Yuteng Wan, Huihua Li, Jinyun Liu, Fanli Meng, Zhen Jin, Lingtao Kong, Jinhuai Liu
In order to sensitively detect indoor air contaminants including benzene, formaldehyde, toluene, and acetone, an effective method using a gas sensor based on coral-shaped tin dioxide nanostructures is reported. It is found that the presented gas sensor exhibits obviously enhanced sensing performance toward indoor air contaminants compared with the ones based on some conventional nanostructures, like nanospheres and nanoparticle-based thin film. The mechanism for such fascinating improvement is demonstrated from the nanoscale size-dependent effect by following theoretical models. Our findings not only provide a promising environmental sensor for sensitively detecting indoor air contaminants, but also suggest a general strategy for utilizing the nanoscale effects of nanoparticles in other environmental and energy-related applications, like waste-water absorbents, catalysts, and solar cells.
Optical temperature sensing through extraordinary enhancement of green up-conversion emissions for Er–Yb–Mo:Al2O3
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
B. Dong, B.S. Cao, Z.Q. Feng, X.J. Wang, Y.Y. He
The extraordinary enhancement of green up-conversion emissions originated from the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions is obtained for the Er–Yb–Mo:Al2O3 with a 976nm laser diode excitation. It indicates that such green enhancement arises from the high excited state energy transfer with |2F7/2, 3T2> state of the Yb3+–MoO4 2− dimer to the 4F7/2 level of Er3+. Fluorescence intensity ratio (FIR) technique based on the green up-conversion emissions of the Er–Yb–Mo:Al2O3 has been studied as a function of temperature. With an excitation power of 2mW, the maximum of sensitivity and temperature revolution is approximately 0.0051K−1 and 0.3K in the range of 294–973K, respectively. The Er–Yb–Mo:Al2O3 with intense green up-conversion emissions, a higher operating temperature and revolution indicates that it is a promising material for application in optical temperature sensing.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
B. Dong, B.S. Cao, Z.Q. Feng, X.J. Wang, Y.Y. He
The extraordinary enhancement of green up-conversion emissions originated from the 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions is obtained for the Er–Yb–Mo:Al2O3 with a 976nm laser diode excitation. It indicates that such green enhancement arises from the high excited state energy transfer with |2F7/2, 3T2> state of the Yb3+–MoO4 2− dimer to the 4F7/2 level of Er3+. Fluorescence intensity ratio (FIR) technique based on the green up-conversion emissions of the Er–Yb–Mo:Al2O3 has been studied as a function of temperature. With an excitation power of 2mW, the maximum of sensitivity and temperature revolution is approximately 0.0051K−1 and 0.3K in the range of 294–973K, respectively. The Er–Yb–Mo:Al2O3 with intense green up-conversion emissions, a higher operating temperature and revolution indicates that it is a promising material for application in optical temperature sensing.
Lab-on-a-chip spectrophotometric characterization of porcine oocytes
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Rafał Walczak, Patrycja Śniadek, Jan A. Dziuban, Bartosz Kempisty, Marta Jackowska, Paweł Antosik, Jędrzej M. Jaśkowski
The method of quality assessment of the oocytes of breeding animals based on morphological criteria very often leads to unsuccessful in vitro fertilization and pure breeding result. In this paper we present a spectrophotometric methodology utilizing lab-on-a-chip techniques for optical and subjective characterization of porcine oocytes. A set of parameters describing the features of oocytes deduced from collected absorbance spectra of a single oocyte, has been proposed. Differentiation of the spectra of oocytes coming from different sizes of porcine follicle has been observed. The obtained results are the first step towards an objective quality assessment of porcine oocytes, which in the future may be extended to other breeding animals.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Rafał Walczak, Patrycja Śniadek, Jan A. Dziuban, Bartosz Kempisty, Marta Jackowska, Paweł Antosik, Jędrzej M. Jaśkowski
The method of quality assessment of the oocytes of breeding animals based on morphological criteria very often leads to unsuccessful in vitro fertilization and pure breeding result. In this paper we present a spectrophotometric methodology utilizing lab-on-a-chip techniques for optical and subjective characterization of porcine oocytes. A set of parameters describing the features of oocytes deduced from collected absorbance spectra of a single oocyte, has been proposed. Differentiation of the spectra of oocytes coming from different sizes of porcine follicle has been observed. The obtained results are the first step towards an objective quality assessment of porcine oocytes, which in the future may be extended to other breeding animals.
Highly sensitive and selective colorimetric detection of Ag(I) ion using 3,3′,5,5′,-tetramethylbenzidine (TMB) as an indicator
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Sen Liu, Jingqi Tian, Lei Wang, Xuping Sun
In this paper, we report on our recent finding that Ag+ can oxidize 3,3′,5,5′,-tetramethylbenzidine (TMB) to develop a blue color in aqueous solution, leading to a simple approach to colorimetric detection of Ag+ with a detection limit of 50nM. Most importantly, we demonstrate its practical application to detect Ag+ in real sample.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Sen Liu, Jingqi Tian, Lei Wang, Xuping Sun
In this paper, we report on our recent finding that Ag+ can oxidize 3,3′,5,5′,-tetramethylbenzidine (TMB) to develop a blue color in aqueous solution, leading to a simple approach to colorimetric detection of Ag+ with a detection limit of 50nM. Most importantly, we demonstrate its practical application to detect Ag+ in real sample.
Chlorella sp. based biosensor for selective determination of mercury in presence of silver ions
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Jasminder Singh, Susheel K. Mittal
Whole cell based biosensor is prepared by immobilizing Chlorella sp. microbes over glassy carbon electrode. The proposed biosensor is optimized for characteristics like substrate concentration, pH, response time, and durability. The electrode responds linearly in concentration range of 10−14 M to 10−6 M for mercury and showed its rare selectivity over silver, alkali metals, alkaline earth metals and transition metals with an expected life of 14 days.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Jasminder Singh, Susheel K. Mittal
Whole cell based biosensor is prepared by immobilizing Chlorella sp. microbes over glassy carbon electrode. The proposed biosensor is optimized for characteristics like substrate concentration, pH, response time, and durability. The electrode responds linearly in concentration range of 10−14 M to 10−6 M for mercury and showed its rare selectivity over silver, alkali metals, alkaline earth metals and transition metals with an expected life of 14 days.
A spheroid-based biosensor for the label-free detection of drug-induced field potential alterations
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Andreas W. Daus, Paul G. Layer, Christiane Thielemann
A valuable method for evaluating the functional effects of promising candidates in cardiac drug discovery is the analysis of electrophysiological characteristics. In vitro techniques facilitate the investigation of physiological parameters, including action potential generation, conduction, arrhythmia and QT duration, to chemical provocation and at the same time benefit from defined experimental conditions as well as enhanced accessibility. A widespread approach to studying the electrophysiological properties of developing and mature cellular networks in vitro is the multichannel recording of cardiac cells cultured as monolayers on microelectrode arrays. However, common two-dimensional monolayer cell cultures do not accurately reflect in vivo conditions. Cells within a tissue are organized into a complex three-dimensional pattern, and cellular interactions are not limited to a two-dimensional environment. Here, we report on a biosensor that combines the microelectrode array technique with cardiac three-dimensional cellular networks. Fully dissociated primary cells from chicken embryonic hearts were re-aggregated into spheroids. We found that action potentials could be recorded with an excellent signal-to-noise-ratio for up to several weeks. The administration of cardioactive drugs significantly altered the electrophysiological characteristics of the spheroids. Cellular responses were investigated along with the biosensor's potential as a tool for estimating the effectiveness and the risk of adverse reactions of drugs.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Andreas W. Daus, Paul G. Layer, Christiane Thielemann
A valuable method for evaluating the functional effects of promising candidates in cardiac drug discovery is the analysis of electrophysiological characteristics. In vitro techniques facilitate the investigation of physiological parameters, including action potential generation, conduction, arrhythmia and QT duration, to chemical provocation and at the same time benefit from defined experimental conditions as well as enhanced accessibility. A widespread approach to studying the electrophysiological properties of developing and mature cellular networks in vitro is the multichannel recording of cardiac cells cultured as monolayers on microelectrode arrays. However, common two-dimensional monolayer cell cultures do not accurately reflect in vivo conditions. Cells within a tissue are organized into a complex three-dimensional pattern, and cellular interactions are not limited to a two-dimensional environment. Here, we report on a biosensor that combines the microelectrode array technique with cardiac three-dimensional cellular networks. Fully dissociated primary cells from chicken embryonic hearts were re-aggregated into spheroids. We found that action potentials could be recorded with an excellent signal-to-noise-ratio for up to several weeks. The administration of cardioactive drugs significantly altered the electrophysiological characteristics of the spheroids. Cellular responses were investigated along with the biosensor's potential as a tool for estimating the effectiveness and the risk of adverse reactions of drugs.
WO3 sensing properties enhanced by UV illumination: An evidence of surface effect
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
A. Giberti, C. Malagù, V. Guidi
The behaviour of the conductance of a nanostructured WO3-based chemioresistive gas sensor under UV illumination was investigated in a synthetic air and in a pure nitrogen environment. The observed increase in conductance under illumination is expected to depend on interband electronic transitions, being the bandgap of the material smaller than the energy of the incident photons. In the present work we show an evidence that an important contribution to this increase is given by surface barrier modulation rather than interband transitions. Indeed, the conductance variation from the dark to the light was interpreted in terms of a direct effect of the light on the adsorbed oxygen ions.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
A. Giberti, C. Malagù, V. Guidi
The behaviour of the conductance of a nanostructured WO3-based chemioresistive gas sensor under UV illumination was investigated in a synthetic air and in a pure nitrogen environment. The observed increase in conductance under illumination is expected to depend on interband electronic transitions, being the bandgap of the material smaller than the energy of the incident photons. In the present work we show an evidence that an important contribution to this increase is given by surface barrier modulation rather than interband transitions. Indeed, the conductance variation from the dark to the light was interpreted in terms of a direct effect of the light on the adsorbed oxygen ions.
An inward replacement/etching route to controllable fabrication of zinc sulfide nanotube arrays for humidity sensing
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Weixin Zhang, Cheng Feng, Zeheng Yang
Well-aligned arrays of polycrystalline ZnS nanotubes with close-tips have been successfully prepared by using ZnO nanorod arrays grown on zinc substrate as sacrificial precursors. The method is based on chemical conversion and inward etching of the ZnO sacrificial precursors. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images show that the highly ordered ZnS nanotube arrays are 300nm in average diameter, 6–8μm in length and about 60nm in wall thickness. A room temperature photoluminescence-type gas sensing device based on the nanostructured arrays has been established to investigate their humidity sensing properties. ZnS nanotube array-based sensor presents higher response and quicker response/recovery than the intermediate ZnO/ZnS nanorod arrays and the precursor ZnO nanorod arrays, respectively. Moreover, the ZnS nanotube array-based sensor exhibits good linearity in response to relative humidity (RH) and reliable reproducibility in a wide range of RH at room temperature. Compared with powder-form nanomaterials, the as-prepared nanotube arrays as the humidity sensing materials can provide much more open surfaces between neighboring nanotubes and inner surfaces inside the nanotubes and allow for easy diffusion and efficient transportation of sensed gas. As a prototype sensor, the nanotube arrays can avoid tedious process of fabricating a sensor from powder and may hold great potential applications in humidity sensing.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Weixin Zhang, Cheng Feng, Zeheng Yang
Well-aligned arrays of polycrystalline ZnS nanotubes with close-tips have been successfully prepared by using ZnO nanorod arrays grown on zinc substrate as sacrificial precursors. The method is based on chemical conversion and inward etching of the ZnO sacrificial precursors. Field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) images show that the highly ordered ZnS nanotube arrays are 300nm in average diameter, 6–8μm in length and about 60nm in wall thickness. A room temperature photoluminescence-type gas sensing device based on the nanostructured arrays has been established to investigate their humidity sensing properties. ZnS nanotube array-based sensor presents higher response and quicker response/recovery than the intermediate ZnO/ZnS nanorod arrays and the precursor ZnO nanorod arrays, respectively. Moreover, the ZnS nanotube array-based sensor exhibits good linearity in response to relative humidity (RH) and reliable reproducibility in a wide range of RH at room temperature. Compared with powder-form nanomaterials, the as-prepared nanotube arrays as the humidity sensing materials can provide much more open surfaces between neighboring nanotubes and inner surfaces inside the nanotubes and allow for easy diffusion and efficient transportation of sensed gas. As a prototype sensor, the nanotube arrays can avoid tedious process of fabricating a sensor from powder and may hold great potential applications in humidity sensing.
Various photonic crystal bio-sensor configurations based on optical surface modes
23 March 2012,
10:54:13
Publication year:
2012
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Hamza Kurt, Muhammed Necip Erim, Nur Erim
We design a new bio-sensor concept that incorporates photonic crystal (PC) surface modes to sense small refractive index changes. The initial attempt creates optical surface modes by first enlarging and then perforating the radii of rods residing along the end surface of the square-lattice PC. The strongly confined mode which decays both evanescently along transverse to propagation direction interacts with the substance while propagating along the PC-air interface. Due to index change of the ambient medium, the transmission spectrum experiences linear shift with a large dynamic range. The relocation of the surface defects enhances the sensitivity of bio-sensor from ∼8 to ∼93nm/RIU. The second type of investigated PC structure is based on triangular-lattice PC and it provides a surface state bio-sensor with a sensitivity of 117nm/RIU. In addition to these designs, we propose a final structure that incorporates air slot along one side of triangular-lattice PC. We succeeded to obtain a new sensitivity value of 396nm/RIU. The investigation shows that even higher sensitivities can be achieved. The different RIU values are reminiscent of group velocity of the relevant modes which can be extracted from the dispersion analysis. Compact, sensitive and label-free optical sensors based on surface modes may become part of the important applications in opto-fluidic technology and lab-on-a-chip.
Source:Sensors and Actuators B: Chemical, Volume 165, Issue 1
Hamza Kurt, Muhammed Necip Erim, Nur Erim
We design a new bio-sensor concept that incorporates photonic crystal (PC) surface modes to sense small refractive index changes. The initial attempt creates optical surface modes by first enlarging and then perforating the radii of rods residing along the end surface of the square-lattice PC. The strongly confined mode which decays both evanescently along transverse to propagation direction interacts with the substance while propagating along the PC-air interface. Due to index change of the ambient medium, the transmission spectrum experiences linear shift with a large dynamic range. The relocation of the surface defects enhances the sensitivity of bio-sensor from ∼8 to ∼93nm/RIU. The second type of investigated PC structure is based on triangular-lattice PC and it provides a surface state bio-sensor with a sensitivity of 117nm/RIU. In addition to these designs, we propose a final structure that incorporates air slot along one side of triangular-lattice PC. We succeeded to obtain a new sensitivity value of 396nm/RIU. The investigation shows that even higher sensitivities can be achieved. The different RIU values are reminiscent of group velocity of the relevant modes which can be extracted from the dispersion analysis. Compact, sensitive and label-free optical sensors based on surface modes may become part of the important applications in opto-fluidic technology and lab-on-a-chip.
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