Hyerin Song

Microfluidic assay-based optical measurement techniques for cell analysis: A review of recent progress.

Since the early 2000s, microfluidic cell culture systems have attracted significant attention as a promising alternative to conventional cell culture methods and the importance of designing an efficient detection system to analyze cell behavior on a chip in real time is raised. For this reason, various measurement techniques for microfluidic devices have been developed with the development of microfluidic assays for high-throughput screening and mimicking of in vivo conditions. In this review, we discuss optical measurement techniques for microfluidic assays. First of all, the recent development of fluorescence- and absorbance-based optical measurement systems is described. Next, advanced optical detection systems are introduced with respect to three emphases: 1) optimization for long-term, real-time, and in situ measurements; 2) performance improvements; and 3) multimodal analysis conjugations. Moreover, we explore presents future prospects for the establishment of optical detection systems following the development of complex, multi-dimensional microfluidic cell culture assays to mimic in vivo tissue, organ, and human systems.

A Localized Surface Plasmon Resonance Sensor Using Double-Metal-Complex Nanostructures and a Review of Recent Approaches

From active developments and applications of various devices to acquire outside and inside information and to operate based on feedback from that information, the sensor market is growing rapidly. In accordance to this trend, the surface plasmon resonance (SPR) sensor, an optical sensor, has been actively developed for high-sensitivity real-time detection. In this study, the fundamentals of SPR sensors and recent approaches for enhancing sensing performance are reported. In the section on the fundamentals of SPR sensors, a brief description of surface plasmon phenomena, SPR, SPR-based sensing applications, and several configuration types of SPR sensors are introduced. In addition, advanced nanotechnology- and nanofabrication-based techniques for improving the sensing performance of SPR sensors are proposed: (1) localized SPR (LSPR) using nanostructures or nanoparticles; (2) long-range SPR (LRSPR); and (3) double-metal-layer SPR sensors for additional performance improvements. Consequently, a high-sensitivity, high-biocompatibility SPR sensor method is suggested. Moreover, we briefly describe issues (miniaturization and communication technology integration) for future SPR sensors.

Current achievements of nanoparticle applications in developing optical sensing and imaging techniques

Metallic nanostructures have recently been demonstrated to improve the performance of optical sensing and imaging techniques due to their remarkable localization capability of electromagnetic fields. Particularly, the zero-dimensional nanostructure, commonly called a nanoparticle, is a promising component for optical measurement systems due to its attractive features, e.g., ease of fabrication, capability of surface modification and relatively high biocompatibility. This review summarizes the work to date on metallic nanoparticles for optical sensing and imaging applications, starting with the theoretical backgrounds of plasmonic effects in nanoparticles and moving through the applications in Raman spectroscopy and fluorescence biosensors. Various efforts for enhancing the sensitivity, selectivity and biocompatibility are summarized, and the future outlooks for this field are discussed. Convergent studies in optical sensing and imaging have been emerging field for the development of medical applications, including clinical diagnosis and therapeutic applications.

Biomimetic self-templating optical structures fabricated by genetically engineered M13 bacteriophage

Here, we describe a highly sensitive and selective surface plasmon resonance sensor system by utilizing self-assembly of genetically engineered M13 bacteriophage. About 2700 copies of genetically expressed peptide copies give superior selectivity and sensitivity to M13 phage-based SPR sensor. Furthermore, the sensitivity of the M13 phage-based SPR sensor was enhanced due to the aligning of receptor matrix in specific direction. Incorporation of specific binding peptide (His Pro Gln: HPQ) gives M13 bacteriophage high selectivity for the streptavidin. Our M13 phage-based SPR sensor takes advantage of simplicity of self-assembly compared with relatively complex photolithography techniques or chemical conjugations. Additionally, designed structure which is composed of functionalized M13 bacteriophage can simultaneously improve the sensitivity and selectivity of SPR sensor evidently. By taking advantages of the genetic engineering and self-assembly, we propose the simple method for fabricating novel M13 phage-based SPR sensor system which has a high sensitivity and high selectivity.

Plasmonic signal enhancements using randomly distributed nanoparticles on a stochastic nanostructure substrate

ABSTRACT The surface-enhanced Raman spectrum was investigated through a numerical model and experiments constructed based on the stochastic Ag nanoislands (AgNIs) substrate. By a rigorous coupled-wave analysis (RCWA) method, the basic properties of electric field were calculated for numerical analysis. The plasmonic coupling between Au nanoparticles (AuNPs) and AgNI substrate was optimized by changing the position of AuNPs on the Ag nanostructured substrate. Furthermore, we experimentally confirmed that AgNIs substrate enable that the intensity of Raman spectra were dramatically improved up to ∼20-fold compared to that of a silver thin film as we expected in numerical calculations. The results gained in this work suggest that we could significantly enhance the Raman signal using easily fabricable AgNI substrates, and can provide the potential applications, such as food, pharmaceutical, and security inspections.

Identification of Endocrine Disrupting Chemicals using a Virus-Based Colorimetric Sensor

A simple and portable colorimetric sensor based on M13 bacteriophage (phage) was devised to identify a class of endocrine disrupting chemicals, including benzene, phthalate, and chlorobenzene derivatives. Arrays of structurally and genetically modified M13 bacteriophage were fabricated so as to produce a biomimetic colorimetric sensor, and color changes in the phage arrays in response to several benzene derivatives were characterized. The sensor was also used to classify phthalate and chlorobenzene derivatives as representatives of endocrine disrupting chemicals. The characteristic color patterns obtained on exposure to various benzene derivatives enabled similar chemical structures in the vapor phase to be classified. Our sensing approach based on the use of a genetically surface modified M13 bacteriophage offers a promising platform for portable, simple environmental monitors that could be extended for use in numerous application areas, including food monitoring, security monitoring, explosive risk assessment, and point of care testing.

Virus based Full Colour Pixels using a Microheater.

Mimicking natural structures has been received considerable attentions, and there have been a few practical advances. Tremendous efforts based on a self-assembly technique have been contributed to the development of the novel photonic structures which are mimicking nature’s inventions. We emulate the photonic structures from an origin of colour generation of mammalian skins and avian skin/feathers using M13 phage. The structures can be generated a full range of RGB colours that can be sensitively switched by temperature and substrate materials. Consequently, we developed an M13 phage-based temperature-dependent actively controllable colour pixels platform on a microheater chip. Given the simplicity of the fabrication process, the low voltage requirements and cycling stability, the virus colour pixels enable us to substitute for conventional colour pixels for the development of various implantable, wearable and flexible devices in future.

Emerging optical spectroscopy techniques for biomedical applications—A brief review of recent progress

ABSTRACT Optical measurement methods are widely employed in both industrial and medical fields for two reasons: (1) they are non-invasive and (2) they have a high resolution. Among the various optical methods currently available, those based on spectroscopy are actively employed to monitor multiple factors using spectral information. In this review article, three categories of optical spectroscopic methods for biomedical diagnosis are discussed: (1) in vitro preclinical diagnosis using optical spectroscopy, (2) non-invasive early-stage diagnosis based on optical spectroscopy at the surface of the skin and (3) minimally-invasive diagnosis using spectroscopy-integrated endoscopies. We also highlight the advances in nanomaterials, molecular probes, and photonic system constructions that have led to improvements in the sensitivity, diagnostic speed, and capability to analyze multiple medical parameters. Additionally, we briefly discuss the future prospects of these spectroscopic applications and the combination of optical techniques with information technology.

Optimization of a Plasmon Enhanced Field Emitter Array Using a Nano-Tip-Based Plasmonic Double-Gate Structure

A nano-tip-based plasmonic double-gate structure (NPDS) excited by the surface plasmon polariton (SPP) resonance of the gate electrode has recently been proposed to achieve the specifications of the UV laser-induced copper cathode. The function of the NPDS is to generate a high bunch charge via near-infrared laser-induced field emission without increasing the cathode size. In this study, we report detailed numerical studies of the proposed NPDS to elucidate the physical mechanism of SPP propagation and light-tip coupling via internal SPP resonance. The simulation results show the relationship between the internal SPP resonance and the tip-light coupling in the NPDS, and the feasibility to achieve significant field emission enhancements with the NPDS. Understanding the internal SPP field in the plasmonic double-gate structure and the light field-tip coupling process in the NPDS is of practical importance in designing field emitter devices and could become an important factor in future high-brightness free-electron laser cathodes and high-sensitivity optical biosensors.

The trapezoidal nanostructure based surface plasmon resonance

The surface plasmon erupted by bare metallic film has limitation of localizing high intensity field. Thus, nanostructures on the metallic film (such as nanowire, nanopost) have been used to enhance the Plasmon field by antenna effect. In the case of nanowire, field is highly localized at the sharpened edge of the nanowire. If there is an additional enhancing factor such as a gap between the edges of the nanostructures, area of highly localized field is formed. By adopting reversed trapezoidal structure, we expected to control area and intensity of highly localized plasmon field from both the nano-antenna effect and the gap plasmonic effect. So, we simulated trapezoidal nanowire structure changing the ratio of bottom length and top length of nanostructure. Then we can observe the variation of Plasmon field and intensity. In addition, we can obtain unusual result that the intensity of Plasmon field is highly reduced at specific ratio of bottom length and top length.