Jun Kameoka - Academia.edu (original) (raw)
Papers by Jun Kameoka
Journal of Photopolymer Science and Technology, 2006
Scientific Reports
We have developed a microscale hydraulic soft gripper and demonstrated the handling of an insect ... more We have developed a microscale hydraulic soft gripper and demonstrated the handling of an insect without damage. This gripper is built on Polydimethylsiloxane (PDMS) with the soft material casting technique to form three finger-like columns, which are placed on a circular membrane. The fingers have a length of 1.5 mm and a diameter of 300 µm each; the distance between the two fingers is 600 µm of center-to-center distance. A membrane as a 150 µm soft film is built on top of a cylindrical hollow space. Applying pressure to the interior space can bend the membrane. Bending the membrane causes the motion of opening/closing of the gripper, and as a result, the three fingers can grip an object or release it. The PDMS was characterized, and the experimental results were used later in Abaqus software to simulate the gripping motion. The range of deformation of the gripper was investigated by simulation and experiment. The result of the simulation agrees with the experiments. The maximum 54...
IECB 2022, Feb 14, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This thesis works deals with the fabrication and characterization of Josephson Junctions. An upgr... more This thesis works deals with the fabrication and characterization of Josephson Junctions. An upgrade over the existing fabricating process with the aim of integrating Josephson Junctions with hetero-structure based HEMT devices was the main aim of this research work. In order to achieve this, new fabrication technique with aim of fabricating small area overlap junction is presented. Josephson Junctions are a Metal-Insulator-Metal capacitor, with both of its electrodes as superconductor metals having femto Farad capacitance and low resistance.
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), 2020
A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucos... more A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucose test strips. This paper-based glucose sensor is prepared with molecularly imprinted (MIP) polyaniline (PANI) electrode. The determination of glucose concentrations was studied by the impedance change of the paper sensor before and after the blood samples dispensing at a low frequency. A comparison of the linear and polynomial regression was applied to analyze the impedance ratio as a function of glucose concentrations. The proposed glucose paper sensor showed a limit of detection (LoD) of 1.135 mM. This novel and non-enzymatic paper sensor suggests a low-cost glucose test assay and can improve the quality of routine testing for diabetic patients.
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), 2020
A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucos... more A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucose test strips. This paper-based glucose sensor is prepared with molecularly imprinted (MIP) polyaniline (PANI) electrode. The determination of glucose concentrations was studied by the impedance change of the paper sensor before and after the blood samples dispensing at a low frequency. A comparison of the linear and polynomial regression was applied to analyze the impedance ratio as a function of glucose concentrations. The proposed glucose paper sensor showed a limit of detection (LoD) of 1.135 mM. This novel and non-enzymatic paper sensor suggests a low-cost glucose test assay and can improve the quality of routine testing for diabetic patients.
Micromachines
An open-water wave energy converter (OWEC) made of a new soft platform has been developed by comb... more An open-water wave energy converter (OWEC) made of a new soft platform has been developed by combining piezoelectric macro-fiber composites (MFCs) and a low-cost elastomer. In the past decades, numerous types of water wave energy conversion platform have been developed and investigated, from buoys to overtopping devices. These harvesters mainly use electromagnetic-based generators, and they have faced challenges such as their enormous size, high deployment and maintenance costs, and negative effects on the environment. These problems hinder their practicality and competitiveness. In this paper, a soft open-water wave energy converter is introduced which integrates piezoelectric MFCs and bubble wrap into an elastomer sheet. The performance of the OWEC was investigated in a wave flume as a floatable structure. The maximum 29.7 µW energy harvested from the small OWEC represents a promising energy conversion performance at low frequencies (<2 Hz). The elastomer was able to protect th...
Nanofluidics
Nanofluidic system can be used as powerful tool for detecting single molecules through fluorescen... more Nanofluidic system can be used as powerful tool for detecting single molecules through fluorescence correlation spectroscopy (FCS). Several types of nanofluidic channels, such as hollow nanofibres or nanotrenches, can be constructed on quartz wafers, though electrospinning and nanolithography, respectively. The advantages of nanofluidic channels in molecule detection are not only in reducing the amount of volume of analyte, but also for improving electrokinetic molecule transport. Therefore, small molecules, like proteins or DNA, can be detected in nanochannels. Furthermore, nanofluidic channels can be used to monitor protein–protein, post translational modification, protein–DNA, and protein–RNA interactions, which rely on labelling proteins of interest within fluorescent molecules, in tissue samples directly. Based on these results, nanofluidic channels can be used in diagnostic application for early diagnosis of cancers and drug screenings.
SPIE Proceedings, 2016
Signal transductions including multiple protein post-translational modifications (PTM), protein-p... more Signal transductions including multiple protein post-translational modifications (PTM), protein-protein interactions (PPI), and protein-nucleic acid interaction (PNI) play critical roles for cell proliferation and differentiation that are directly related to the cancer biology. Traditional methods, like mass spectrometry, immunoprecipitation, fluorescence resonance energy transfer, and fluorescence correlation spectroscopy require a large amount of sample and long processing time. “microchannel for multiple-parameter analysis of proteins in single-complex (mMAPS)”we proposed can reduce the process time and sample volume because this system is composed by microfluidic channels, fluorescence microscopy, and computerized data analysis. In this paper, we will present an automated mMAPS including integrated microfluidic device, automated stage and electrical relay for high-throughput clinical screening. Based on this result, we estimated that this automated detection system will be able to screen approximately 150 patient samples in a 24-hour period, providing a practical application to analyze tissue samples in a clinical setting.
Colloidal Nanoparticles for Biomedical Applications XI, 2016
Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanop... more Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a 'target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.
Optical Diagnostics and Sensing XVI: Toward Point-of-Care Diagnostics, 2016
Rapid assessment of radiation exposure to sensitive organs like the gut is extremely important fo... more Rapid assessment of radiation exposure to sensitive organs like the gut is extremely important for large populations exposed to ionized radiation, for instance during warfare. Recent results have shown that plasma citrulline levels appear to track gut function after irradiation levels in mice and humans. The current ways to monitor blood citrulline levels are bulky, laborious, time-consuming and expensive methods. Therefore, an optofludic point-of-care (POC) system using surface enhanced Raman spectroscopy to measure plasma citrulline as a marker for radiation exposure that overcomes the above issues is being developed. As a first step toward development of this system four colloidal nanoparticles, spherical gold, silver cubes, silica-gold nanoshells, and silver-gold nanocages have been analyzed for use in the POC system. Transmission electron microscopy (TEM) images have been taken of each nanoparticle to visualize the morphology of the nanoparticles, which is vital for SERS. Ultraviolet-visible (UV/Vis) spectroscopy was also collected to verify the extinction spectra for each nanoparticle was in resonance with the excitation wavelength. The nanoparticles were functionalized with mercaptobenzoic acid (MBA), a Raman reporter molecule, and SERS spectra were collected to determine which has better utility in a novel micro-to-nanochannel. The data showed that the silver nanocubes have a larger enhancement factor than the gold nanospheres, nanoshells, or nanocages. Currently, these nanocubes are being functionalized with the citulline for assessing the concentration sensitivity and dynamic range for ultimate use as a marker for radiation.
Handbook of Optofluidics, 2010
Microfluidics and Nanofluidics, 2009
An optofluidic device is reported in this paper that can highly improve the robustness of surface... more An optofluidic device is reported in this paper that can highly improve the robustness of surface-enhanced Raman scattering (SERS) detection and provide fingerprint information of proteins with a concentration in the nanogram per liter range within minutes. Moreover, the conformational change of protein can also be obtained using this device. Fabricated by standard photolithography processes, the optofluidic device has a step microfluidicnanofluidic structure, which provides robust SERS detection. The sensitivity of the device is investigated using insulin and albumin as target analytes at a concentration of 0.9 ng/L. The ability to detect conformational changes of proteins using this technology is also shown by probing these analytes before and after their denaturation.
Micro Total Analysis Systems 2002, 2002
We have fabricated and tested a new electrospray ionization source integrated with a microfluidic... more We have fabricated and tested a new electrospray ionization source integrated with a microfluidic channel for interfacing to a Time-of-Flight mass spectrometry (TOF MS). A triangle shaped polymeric tip was patterned using an optical lithography and plasma etching from a polymeric thin film deposited on a silicon wafer. The shaped emitter was peeled from a silicon wafer. The emitter tip was aligned at the exit of the microfluidic channel and bonded between two plastic pieces; one of which had a microfluidic channel embossed. Liquid was supplied to the emitter tip via a reservoir hole connected to the embossed microfluidic channel by a syringe pump. A gold wire was inserted into the reservoir as a high voltage supply for an electrospray ionization. The polymeric electrospray source tip was placed 1.0 cm away from an entrance orifice of TOF MS. Berberine was used as a test sample to characterize the performance of the electrospray device. The total ion current was stable for many minutes with fluctuations ofless than 4.0%.
We have developed an optofluidic device that can significantly improve the sensitivity, efficienc... more We have developed an optofluidic device that can significantly improve the sensitivity, efficiency and reproducibility of the surface enhanced Raman spectroscopy (SERS). This device has demonstrated the capalibity of detecting molecules of interest at ultra-low concentration and is able to identify fingerprint signals from multiple analytes. This device can potentially be used for the definitive early stage diagnostics of disease associated with protein conformation change such as Alzheimer's disease (AD) or Bovine Spongiform Encephalopathy (BSE) .
The width and shape of photon burst histograms pose significant limitations to the identification... more The width and shape of photon burst histograms pose significant limitations to the identification of single molecules in micro/nano-fluidic channels, and the nature of these histograms is not fully understood. To reach a deeper understanding, we performed computer simulations based on a Gaussian beam intensity profile with various fluidic channel diameters and assuming (i) a deterministic (noise-free) case, (ii) photon emission/absorption noise, and (iii) photon noise with diffusion. Photon noise in narrow channels yields a Gaussian burst distribution while additional strong diffusion produces skewed histograms. We use the fluctuating residence time picture [Phys. Rev. Lett. 80, 2386-2388 (1998)] and conclude that the skewness of the photon number distribution is caused by the longitudinal diffusive component of the motion of the molecules as they traverse the laser beam. In the case of strong diffusion in narrow channels, this effect leads to a log-normal distribution. We show that...
Photonic burst histograms can be used to identify single protein molecules in micro/nano-fluidic ... more Photonic burst histograms can be used to identify single protein molecules in micro/nano-fluidic channels provided the width of the histogram is narrow. Photonic shot noise and residence time fluctuations, caused by longitudinal diffusion, are the major sources of the histogram width. This Communication is a sequel to an earlier Letter of ours [L. L. Kish et al., Appl. Phys. Lett. 99, 143121 (2011)] and demonstrates that, for a given diffusion coefficient, an increase of the drift velocity enhances the relative shot noise and decreases the relative residence time fluctuations. This leads to an optimum drift velocity which minimizes the histogram width and maximizes the ability to identify single molecules, which is an important result for applications.
Trace detection of the conformational transition of -amyloid peptide (A) from a predominantly r-h... more Trace detection of the conformational transition of -amyloid peptide (A) from a predominantly r-helical structure to -sheet could have a large impact in understanding and diagnosing Alzheimer’s disease. We demonstrate how a novel nanofluidic biosensor using a controlled, reproducible surface enhanced Raman spectroscopy active site was developed to observe A in different conformational states during the A self-assembly process as well as to distinguish A from confounder proteins commonly found in cerebral spinal fluid. Alzheimer’s disease (AD), a progressive neurodegenerative disease and the leading cause of dementia in the aging population, affects 4.5 million people according to the 2000 U.S. census.1 One of the primary pathological hallmarks of Alzheimer’s disease is the presence of insoluble neuritic plaques, composed primarily of -amyloid peptide (A), in the cerebral cortex. A peptide, a natural metabolic byprod-uct, results from the proteolytic cleavage of the amyloid precursor...
Journal of Photopolymer Science and Technology, 2006
Scientific Reports
We have developed a microscale hydraulic soft gripper and demonstrated the handling of an insect ... more We have developed a microscale hydraulic soft gripper and demonstrated the handling of an insect without damage. This gripper is built on Polydimethylsiloxane (PDMS) with the soft material casting technique to form three finger-like columns, which are placed on a circular membrane. The fingers have a length of 1.5 mm and a diameter of 300 µm each; the distance between the two fingers is 600 µm of center-to-center distance. A membrane as a 150 µm soft film is built on top of a cylindrical hollow space. Applying pressure to the interior space can bend the membrane. Bending the membrane causes the motion of opening/closing of the gripper, and as a result, the three fingers can grip an object or release it. The PDMS was characterized, and the experimental results were used later in Abaqus software to simulate the gripping motion. The range of deformation of the gripper was investigated by simulation and experiment. The result of the simulation agrees with the experiments. The maximum 54...
IECB 2022, Feb 14, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
This thesis works deals with the fabrication and characterization of Josephson Junctions. An upgr... more This thesis works deals with the fabrication and characterization of Josephson Junctions. An upgrade over the existing fabricating process with the aim of integrating Josephson Junctions with hetero-structure based HEMT devices was the main aim of this research work. In order to achieve this, new fabrication technique with aim of fabricating small area overlap junction is presented. Josephson Junctions are a Metal-Insulator-Metal capacitor, with both of its electrodes as superconductor metals having femto Farad capacitance and low resistance.
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), 2020
A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucos... more A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucose test strips. This paper-based glucose sensor is prepared with molecularly imprinted (MIP) polyaniline (PANI) electrode. The determination of glucose concentrations was studied by the impedance change of the paper sensor before and after the blood samples dispensing at a low frequency. A comparison of the linear and polynomial regression was applied to analyze the impedance ratio as a function of glucose concentrations. The proposed glucose paper sensor showed a limit of detection (LoD) of 1.135 mM. This novel and non-enzymatic paper sensor suggests a low-cost glucose test assay and can improve the quality of routine testing for diabetic patients.
2020 42nd Annual International Conference of the IEEE Engineering in Medicine & Biology Society (EMBC), 2020
A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucos... more A low-cost and enzyme-free glucose paper sensor is presented as a promising alternative to glucose test strips. This paper-based glucose sensor is prepared with molecularly imprinted (MIP) polyaniline (PANI) electrode. The determination of glucose concentrations was studied by the impedance change of the paper sensor before and after the blood samples dispensing at a low frequency. A comparison of the linear and polynomial regression was applied to analyze the impedance ratio as a function of glucose concentrations. The proposed glucose paper sensor showed a limit of detection (LoD) of 1.135 mM. This novel and non-enzymatic paper sensor suggests a low-cost glucose test assay and can improve the quality of routine testing for diabetic patients.
Micromachines
An open-water wave energy converter (OWEC) made of a new soft platform has been developed by comb... more An open-water wave energy converter (OWEC) made of a new soft platform has been developed by combining piezoelectric macro-fiber composites (MFCs) and a low-cost elastomer. In the past decades, numerous types of water wave energy conversion platform have been developed and investigated, from buoys to overtopping devices. These harvesters mainly use electromagnetic-based generators, and they have faced challenges such as their enormous size, high deployment and maintenance costs, and negative effects on the environment. These problems hinder their practicality and competitiveness. In this paper, a soft open-water wave energy converter is introduced which integrates piezoelectric MFCs and bubble wrap into an elastomer sheet. The performance of the OWEC was investigated in a wave flume as a floatable structure. The maximum 29.7 µW energy harvested from the small OWEC represents a promising energy conversion performance at low frequencies (<2 Hz). The elastomer was able to protect th...
Nanofluidics
Nanofluidic system can be used as powerful tool for detecting single molecules through fluorescen... more Nanofluidic system can be used as powerful tool for detecting single molecules through fluorescence correlation spectroscopy (FCS). Several types of nanofluidic channels, such as hollow nanofibres or nanotrenches, can be constructed on quartz wafers, though electrospinning and nanolithography, respectively. The advantages of nanofluidic channels in molecule detection are not only in reducing the amount of volume of analyte, but also for improving electrokinetic molecule transport. Therefore, small molecules, like proteins or DNA, can be detected in nanochannels. Furthermore, nanofluidic channels can be used to monitor protein–protein, post translational modification, protein–DNA, and protein–RNA interactions, which rely on labelling proteins of interest within fluorescent molecules, in tissue samples directly. Based on these results, nanofluidic channels can be used in diagnostic application for early diagnosis of cancers and drug screenings.
SPIE Proceedings, 2016
Signal transductions including multiple protein post-translational modifications (PTM), protein-p... more Signal transductions including multiple protein post-translational modifications (PTM), protein-protein interactions (PPI), and protein-nucleic acid interaction (PNI) play critical roles for cell proliferation and differentiation that are directly related to the cancer biology. Traditional methods, like mass spectrometry, immunoprecipitation, fluorescence resonance energy transfer, and fluorescence correlation spectroscopy require a large amount of sample and long processing time. “microchannel for multiple-parameter analysis of proteins in single-complex (mMAPS)”we proposed can reduce the process time and sample volume because this system is composed by microfluidic channels, fluorescence microscopy, and computerized data analysis. In this paper, we will present an automated mMAPS including integrated microfluidic device, automated stage and electrical relay for high-throughput clinical screening. Based on this result, we estimated that this automated detection system will be able to screen approximately 150 patient samples in a 24-hour period, providing a practical application to analyze tissue samples in a clinical setting.
Colloidal Nanoparticles for Biomedical Applications XI, 2016
Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanop... more Conjugation of oligonucleotides or aptamers and their corresponding analytes onto plasmonic nanoparticles mediates the formation of nanoparticle assemblies: molecularly bound bundles of nanoparticles which cause a measurable change in the colloid's optical properties. Here, we present further optimization of a "SERS off" competitive binding assay utilizing plasmonic and magnetic nanoparticles for the detection of the toxin bisphenol A (BPA). The assay involves 1) a 'target' silver nanoparticle functionalized with a Raman reporter dye and PEGylated BPA-binding DNA aptamers, and 2) a version of the toxin BPA, bisphenol A diglycidyl ether (BADGE), PEGylated and immobilized onto a silver coated magnetic 'probe' nanoparticle. When mixed, these target and probe nanoparticles cluster into magnetic dimers and trimers and an enhancement in their SERS spectra is observed. Upon introduction of free BPA in its native form, target AgNPs are competitively freed; reversing the nanoparticle assembly and causing the SERS signal to "turn-off" and decrease in response to the competitive binding event. The assay particles were housed inside two types of optofluidic chips containing magnetically active nickel pads, in either a straight or spotted pattern, and both Fe2O3 and Fe2CoO4 were compared as magnetic cores for the silver coated probe nanoparticle. We found that the Ag@ Fe2O3 particles were, on average, more uniform in size and more stable than Ag@ Fe2CoO4, while the addition of cobalt significantly improved the collection time of particles within the magnetic chips. Using 3D Raman mapping, we found that the straight channel design with the Ag@ Fe2O3 particles provided the most uniform nanoparticle organization, while the spotted channel design with Ag@ Fe2CoO4 demonstrated a larger SERS enhancement, and thus a lower limit of detection.
Optical Diagnostics and Sensing XVI: Toward Point-of-Care Diagnostics, 2016
Rapid assessment of radiation exposure to sensitive organs like the gut is extremely important fo... more Rapid assessment of radiation exposure to sensitive organs like the gut is extremely important for large populations exposed to ionized radiation, for instance during warfare. Recent results have shown that plasma citrulline levels appear to track gut function after irradiation levels in mice and humans. The current ways to monitor blood citrulline levels are bulky, laborious, time-consuming and expensive methods. Therefore, an optofludic point-of-care (POC) system using surface enhanced Raman spectroscopy to measure plasma citrulline as a marker for radiation exposure that overcomes the above issues is being developed. As a first step toward development of this system four colloidal nanoparticles, spherical gold, silver cubes, silica-gold nanoshells, and silver-gold nanocages have been analyzed for use in the POC system. Transmission electron microscopy (TEM) images have been taken of each nanoparticle to visualize the morphology of the nanoparticles, which is vital for SERS. Ultraviolet-visible (UV/Vis) spectroscopy was also collected to verify the extinction spectra for each nanoparticle was in resonance with the excitation wavelength. The nanoparticles were functionalized with mercaptobenzoic acid (MBA), a Raman reporter molecule, and SERS spectra were collected to determine which has better utility in a novel micro-to-nanochannel. The data showed that the silver nanocubes have a larger enhancement factor than the gold nanospheres, nanoshells, or nanocages. Currently, these nanocubes are being functionalized with the citulline for assessing the concentration sensitivity and dynamic range for ultimate use as a marker for radiation.
Handbook of Optofluidics, 2010
Microfluidics and Nanofluidics, 2009
An optofluidic device is reported in this paper that can highly improve the robustness of surface... more An optofluidic device is reported in this paper that can highly improve the robustness of surface-enhanced Raman scattering (SERS) detection and provide fingerprint information of proteins with a concentration in the nanogram per liter range within minutes. Moreover, the conformational change of protein can also be obtained using this device. Fabricated by standard photolithography processes, the optofluidic device has a step microfluidicnanofluidic structure, which provides robust SERS detection. The sensitivity of the device is investigated using insulin and albumin as target analytes at a concentration of 0.9 ng/L. The ability to detect conformational changes of proteins using this technology is also shown by probing these analytes before and after their denaturation.
Micro Total Analysis Systems 2002, 2002
We have fabricated and tested a new electrospray ionization source integrated with a microfluidic... more We have fabricated and tested a new electrospray ionization source integrated with a microfluidic channel for interfacing to a Time-of-Flight mass spectrometry (TOF MS). A triangle shaped polymeric tip was patterned using an optical lithography and plasma etching from a polymeric thin film deposited on a silicon wafer. The shaped emitter was peeled from a silicon wafer. The emitter tip was aligned at the exit of the microfluidic channel and bonded between two plastic pieces; one of which had a microfluidic channel embossed. Liquid was supplied to the emitter tip via a reservoir hole connected to the embossed microfluidic channel by a syringe pump. A gold wire was inserted into the reservoir as a high voltage supply for an electrospray ionization. The polymeric electrospray source tip was placed 1.0 cm away from an entrance orifice of TOF MS. Berberine was used as a test sample to characterize the performance of the electrospray device. The total ion current was stable for many minutes with fluctuations ofless than 4.0%.
We have developed an optofluidic device that can significantly improve the sensitivity, efficienc... more We have developed an optofluidic device that can significantly improve the sensitivity, efficiency and reproducibility of the surface enhanced Raman spectroscopy (SERS). This device has demonstrated the capalibity of detecting molecules of interest at ultra-low concentration and is able to identify fingerprint signals from multiple analytes. This device can potentially be used for the definitive early stage diagnostics of disease associated with protein conformation change such as Alzheimer's disease (AD) or Bovine Spongiform Encephalopathy (BSE) .
The width and shape of photon burst histograms pose significant limitations to the identification... more The width and shape of photon burst histograms pose significant limitations to the identification of single molecules in micro/nano-fluidic channels, and the nature of these histograms is not fully understood. To reach a deeper understanding, we performed computer simulations based on a Gaussian beam intensity profile with various fluidic channel diameters and assuming (i) a deterministic (noise-free) case, (ii) photon emission/absorption noise, and (iii) photon noise with diffusion. Photon noise in narrow channels yields a Gaussian burst distribution while additional strong diffusion produces skewed histograms. We use the fluctuating residence time picture [Phys. Rev. Lett. 80, 2386-2388 (1998)] and conclude that the skewness of the photon number distribution is caused by the longitudinal diffusive component of the motion of the molecules as they traverse the laser beam. In the case of strong diffusion in narrow channels, this effect leads to a log-normal distribution. We show that...
Photonic burst histograms can be used to identify single protein molecules in micro/nano-fluidic ... more Photonic burst histograms can be used to identify single protein molecules in micro/nano-fluidic channels provided the width of the histogram is narrow. Photonic shot noise and residence time fluctuations, caused by longitudinal diffusion, are the major sources of the histogram width. This Communication is a sequel to an earlier Letter of ours [L. L. Kish et al., Appl. Phys. Lett. 99, 143121 (2011)] and demonstrates that, for a given diffusion coefficient, an increase of the drift velocity enhances the relative shot noise and decreases the relative residence time fluctuations. This leads to an optimum drift velocity which minimizes the histogram width and maximizes the ability to identify single molecules, which is an important result for applications.
Trace detection of the conformational transition of -amyloid peptide (A) from a predominantly r-h... more Trace detection of the conformational transition of -amyloid peptide (A) from a predominantly r-helical structure to -sheet could have a large impact in understanding and diagnosing Alzheimer’s disease. We demonstrate how a novel nanofluidic biosensor using a controlled, reproducible surface enhanced Raman spectroscopy active site was developed to observe A in different conformational states during the A self-assembly process as well as to distinguish A from confounder proteins commonly found in cerebral spinal fluid. Alzheimer’s disease (AD), a progressive neurodegenerative disease and the leading cause of dementia in the aging population, affects 4.5 million people according to the 2000 U.S. census.1 One of the primary pathological hallmarks of Alzheimer’s disease is the presence of insoluble neuritic plaques, composed primarily of -amyloid peptide (A), in the cerebral cortex. A peptide, a natural metabolic byprod-uct, results from the proteolytic cleavage of the amyloid precursor...