Optofluidic bio-lasers are an emerging technology for next generation biochemical detection and clinical applications. Recent advances has been made to achieve lasing from biomolecules and single living cells. Tissues, which consist of cells embedded in extracellular matrix, mimic more closely the actual complex biological environment in a living body and therefore are of more practical significance in medicine. In this talk, I will introduce the current implementations of “optofluidic tissue lasers”, including lasing from human whole blood and cancer tissue biopsies. Distinct and controllable laser emissions from tissues thus enable highly multiplexed detection of tissues, which opens a door to a plethora of biomedical applications in bio-imaging with superior contrast and high spectral/spatial resolution. Finally, discussion and outlook is made on the strategies to differentiate/monitor various diseases through tissue lasers and to pioneer novel on-chip devices for future clinical diagnosis, prognosis, and therapy.

Abstract

Portable electronic devices and wireless communication enable a broad range of applications including environmental surveillance, food safety monitoring and point-of-care testing. Particularly, by incorporating smartphone and microfluidic paper-based device, rapid analysis, mobile laboratories for chemical assay, remote sensing and data management become more available. In this work, we designed and fabricated a 12-unit paper chip for colorimetric detection of Fe, Ni, Cu and Co. Cellphone’s camera was used to capture colorimetric images, and then the RGB values of the color images were converted to grayscale via a custom designed app. The intensity reflecting metal concentrations were processed and analyzed by the same app and a remote server. Log-linear calibration curves were generated for each metal, with method detection limits ranging from 0.8 to 1.2 μg for each metal. The presented device and data processing tools hold a potential to assist mobile sensing, pollution detection and healthcare in low-resource areas.

Keywords: Paper-based microfluidics, Smartphone image processing, Metals detection

Publishing in reputable international journals is an important part of academic life. The process requires time to ensure the suitability of the submission and also, the quality. Finding the right journal is an essential first step. Being out of scope will lead to rejection, regardless of the quality of the work. Furthermore, an inappropriate paper will not reach the intended readership, and may therefore be lost. This presentation will explain the procedure for review, considerations when preparing a paper and also issues such as authors rights and plagiarism.

Molecular breeding of rice is crucial for feeding the world’s rapidly growing population, for limited land resources, superior grain quality, and severe environmental situation[1]. Single nucleotide polymorphism(SNP) is regarded as the third genetic marker, having the potential to increase the speed and cost-effectiveness of genotyping and breeding applications, as well as routine genetic diversity analysis, linkage mapping, and marker-assisted selection in rice[2]. High resolution melting (HRM) analysis is a new methodology for mutation scanning that has gained considerable popularity in recent years[3]. The advantages of HRM for variant scanning include rapid turn-around times, closed-system that greatly reduces contamination risk, directly analysis after PCR, and unconsidering novel variants or genotyping known type[4]. However, due to HRM requiring high temperature resolution during heating process, traditional tube method is difficult to meet the demands for SNP detection in rice molecular breeding. Here we reported a microfluidic chip and a real-time PCR system integrated high precise thermal cycler and online fluorescence detection module (Fig.1/2) [5]. This platform ingeniously utilized the advantage of microfluidic chip, such as heat fast transfered and well-distributed in the chamber. We used Oryza sativa L. and 9311 as the experimental material, and selected a few important SNPs for breeding as our research objects by comparing genomes database of two species. The result demonstrated that this platform can rapidly detected the SNPs through PCR and HRM analysis on the chip (Fig.3/4). It also indicated that the device can be applied widely in applications screening of mutants in molecular breeding.

Zinc Oxide Nanowires (ZnO-NWs) gained a lot of interest due to their diverse and unique semiconductive, optical, and piezoelectric properties. ZnO-NWs has been used in different applications such as nanogenerator of electricity ‎[1], chemical sensors ‎[2], photovoltaic cells ‎[3] and recently in water purification ‎[4]. In all those applications, performance is directly related to the actual properties of the ZnO-NWs. The latter properties can be investigated in detail using Scanning Electron Microscopy (SEM), X-Ray Diffraction and High Resolution Transmission Electron Microscopy for the purpose of characterization and optimization of the growth process.

However, once ZnO-NWs are integrated within a microfluidic device, there is a need for a much simpler characterization technique for checking in situ the quality and uniformity of ZnO-NWs during and after their growth. In this work, we take advantage of the strong dependence of the ZnO-NWs properties on their dimensions, density and possible contamination, considered here as quality indicators. We also note that those indicators can be obtained by optical measurement of effective thickness (d_eff), effective refraction index (n_eff) and light absorption, respectively, of the ZnO-NW array, which is considered here as a thin film layer (Fig.1). We propose herein a simple and time-saving method measuring all those parameters in the same experiment, based on the reflection spectral response in the Ultraviolet (UV), Visible (Vis) and Near-Infra-Red (NIR) range.

The purity of the ZnO growth is observed through absorbance, while, ZnO-NWs density (n_eff) and height can be obtained from the reflection response, which reveals interference patterns in the ZnO-NWs layer. The optical path (d_eff x n_eff) is retrieved by the Free Spectral Range (FSR).

The ZnO-NWs are synthesized using the hydrothermal method ‎[5]. Typical results for different growth times are shown in Fig. 2. A top view of the synthesized NWs array grown over silicon is shown in Fig. 1 together with illustrative schematic of the synthesized NWs cross-section at different positions. Denser and longer NWs are synthesized on the edge of the chip while the density and length decrease moving away from the edge. The n_eff of the ZnO-NWs layer is in-between air and ZnO refractive indices, based on the ZnO-NWs density. The measured absorbance (normalized to silicon) is shown in Fig. 3 for ZnO growth for 2 hours (2h) at different positions. Absorbance cut-off is observed around 370 nm corresponding to the ZnO bandgap absorption. The ripples correspond to the reflection response of the ZnO thin film where the smallest FSR observed at the edge relates to the denser ZnO-NWs growth (higher n_eff) compared to the other two regions. Fig. 4 relates to a 3h growth where some residual Zn(OH)_x masking the reflection response at the edge in addition to the expanded absorption. Besides density, the purity of the synthesized ZnO can be evaluated by the absorbance cut-off wavelength. However, pure ZnO has cut-off around 370 nm, the non-pure ZnO have higher cut-off (Fig. 5) for the 4h growth where the purest ZnO is synthesized at the center of the chip

Understanding light interaction with microorganisms is of crucial importance in relation to the development of bio-fuels, solar cells, bio-lasers, as well as of fundamental interest in biophotonics, optofluidics, soft-matter physics, and life science. Despite of significant efforts in the study of optical properties of biological media, it is commonly pictured that light cannot penetrate deeply into biological environments due to their strong scattering loss and weak optical nonlinearity. In this talk, we report on our recent demonstration of robust propagation and enhanced transmission of a light beam over long distances through a biological suspension of marine bacteria. By deliberately altering the host environments, we show dramatic change of nonlinear propagation dynamics of the light beam, while the viability of the microorganisms remains intact. A theoretical model is developed to show that a nonlocal nonlinearity mediated by optical forces acting on the bacteria could explain the observed phenomenon. In particular, we found that the scattering force from light in the forward direction appears to play a pivotal role in forming the “biological” waveguide that is able to sustain needle-like light propagation through the cell susupension. These findings may open up new opportunities in developing bio-soft-matter systems with tunable optical nonlinearities for various applications.

An innovative label free optical fiber biosensor based on Mach-Zehender interferometer for Bovine Serum Albumin density detection will be introduced. The fiber biosensor employs a micro-cavity within the single mode fiber to form Mach-Zehender interference. The device is fabricated by means of femtosecond laser micromachining and chemical etching. Such a fiber interferometer exhibits an ultrahigh refractive index sensitivity of -10055 nm/RIU. The biosensor exerted the BSA solution concentration sensitivity of -38.9 nm/(mg/mL) and detection limit of 257 ng/mL respectively.

In this paper, we present a novel platform based on a hybrid photonic cavity with metal-organic framework (MOF) coatings for VOCs detection. We have fabricated a compact gas sensor with detection limitation ranging from 29 to 99 ppb for various VOCs including styrene, toluene, benzene, propylene and methanol. Our results demonstrate that MOF coatings have significant potential in enhancing the sensitivity of miniaturized gas sensors.

Our design fully utilizes the strong absorption properties of MOFs[1] and the ultra-high quality factor (Q-factor) of photonic resonator structures. We selected ZIF-8 as the external MOF coating material because of its high surface area (1840 m² g^-1), hydrophobicity, good water stability, and high light transmittance in NIR.^{[2, 3]} As shown in Fig 1, ZIF-8 pre-concentration coating was grown on the Si₃N₄ waveguide based micro-ring resonator (MRR) by a layer-by-layer intergrowth process, after which the coating was patterned using lithography and etched by sulfuric acid. An illustration of the experimental apparatus is shown in Fig 2.

The resonant wavelength of the MRR is strongly dependent on the changes of ZIF-8 RI induced by gas adsorption. As shown in Fig 3, the resonant wavelength exhibited a blueshift firstly, and then started to redshift upon exposure to each gas with a concentration of 100 ppm. The equilibrium during the exposure time is between 30 to 45 minutes for these five VOC vapours, and the final shifts of the resonance are 172 pm, 341 pm, 282 pm, 131 pm, and 101 pm for methanol, propylene, benzene, toluene, and styrene, respectively. Compared to a MRR without pre-concentration/absorption layers, the hybrid photonic-MOF devices can improve the sensitivity up to 568, 1025, 621, 300, and 220 times for methanol, propylene, benzene, toluene, and styrene, respectively, as shown in Fig 4. Besides, as the resonant wavelength variation induced by the environmental temperature variation and tunable laser instability is around +/- 0.1 pm in the experiments as previous mentioned,^[4] the detection limits for these five VOC vapours are determined in the range from 29 to 99 ppb.

Achieving broadband total light absorption of unpolarized light within a subwavelength
ultrathin film is critical for optoelectronic applications such as photovoltaics,
photodetectors, thermal emitters and optical modulators. Here we experimentally
demonstrate a low-cost and scalable multilayer graphene ultra-broadband total light
absorber of record-high 90% of unpolarized light absorption at near infrared
wavelengths with a bandwidth of more than 300 nm. The thin metamaterial consists of
alternating monolayer graphene and dielectric material prepared by a low-cost wet
chemical layer-by-layer method. A simple grating is fabricated using flexible
femtosecond laser writing that simultaneously removes the graphene in the ablated
regions and converts the remaining graphene oxide to graphene via photo-reduction.
Our results open a novel, flexible and viable approach to practical applications of
nanostructured photonic devices based on 2D materials, which require strong
absorption.