Microphotonics and Nanoislands Integrated Lab-on-Chips (LOCs) for the Detection of Growth Hormones in Milk

Lab-on-a-chips (LOCs), alternatively called micro total analysis systems (μTAS) are miniaturized chemical or biological analytical devices that integrate one or several laboratory functions on a single chip. LOCs handle small amount of sample volume and enable the analysis and detection with enhanced performances in short time. This thesis focuses on developing LOC platforms for the detection of growth hormones such as bovine somatotropin (bST) and recombinant bovine somatotropin (rbST) in milk. Bovine somatotropin is a polypeptide growth hormone naturally produced by the anterior pituitary gland in mammals, which has strong influences on the biological effects such as growth, developments and reproductive functions. The bST is useful to increase the milk and meat production. With the emergence of the recombinant DNA technology, large quantities of artificial hormones called recombinant bovine somatotropin (rbST) are produced and used for the production of milk and meat in dairy industry. Use of growth hormones for the production of milk and meat is still controversial due to its potential effects on animal and human health. Hence, there is a huge demand for highly sensitive, rapid and low cost devices for the detection of growth hormones. Currently, the growth hormones are detected by large equipment which needs large amounts of reagents and bio-liquids in addition to longer analysis time. In this context, there is a large demand for developing a miniaturized bio-analytical platform for the rapid and precise screening of growth hormones in milk. In this thesis, development of LOC platforms for the labeled and label-free detection of growth hormone is attempted. The labeled detection of the rbST was demonstrated in a low cost lab-on-a-chip platform fabricated by integrating an optical microfluidic system on silica-on-silicon (SOS) waveguide with a PDMS (polydimethylsiloxane) microfluidic chip. In order to achieve higher sensitivity and specificity, a novel cascaded waveguide coupler (CWC) system is designed and fabricated on the silica-on-silicon platform. A novel method of fabricating nano-island morphology is developed for the label-free detection of bovine growth hormone. Experimental and theoretical analysis of tuning the gold nano-island morphology is investigated and implemented for the label-free detection of growth hormone. Subsequently, the nano-island morphology is integrated into a PDMS microfluidic chip and a LOC is realized. A low cost, all polymer lab-on-a-chip is developed by integrating silver-PDMS nanocomposite by in-situ synthesis of nano-composite inside the microfluidic chip and detection of growth hormone is also demonstrated. The nano-islands are integrated into silica-on-silicon waveguides for the development of a nano-enhanced evanescent wave sensor for the detection of rbST. Extraction of growth hormone from milk by solid phase extraction and its detection are also demonstrated. Finally, a monolithically integrated LOC on silica-on-silicon (SOS) comprising of microfluidics, optical waveguides and Echelle grating based spectrometer is realized. The simulation and integration process of a micro-spectrometer with the optical waveguide and microfluidic channel are also presented

Microfluidic coupler for hybrid integrated lab-on-a-chip

Paper presented to the 10th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Florida, 14-16 July 2014.Lab-on-chips (LOCs) or miniaturized total analytical systems (μTAS) are attractive to perform chemical and biological analysis using small amounts of samples in a short time. Micro machined fluidics and optical devices are integral components of LOCs, which are fabricated monolithically or by hybrid integration in order to perform various analytical process in a single chip. In this work, simulation and implementation of a microfluidic coupler for the hybrid integration of an optical microfluidic system by using silica-on-silicon waveguides and polydimethylsiloxane (PDMS) microfluidic chips are demonstrated. The presented microfluidic coupler simplifies the fabrication of optical microfluidic systems by coupling the fluid from the PDMS chip to the micro channel in the silica-onwaveguide. The micro-flow behavior through the coupler is investigated by the simulations carried out using the COMSOL multiphysics and the experiments as well.dc201

Simulation and Implementation of a Morphology-Tuned Gold Nano-Islands Integrated Plasmonic Sensor

This work presents simulation, analysis and implementation of morphology tuning of gold nano-island structures deposited by a novel convective assembly technique. The gold nano-islands were simulated using 3D Finite-Difference Time-Domain (FDTD) techniques to investigate the effect of morphological changes and adsorption of protein layers on the localized surface plasmon resonance (LSPR) properties. Gold nano-island structures were deposited on glass substrates by a novel and low-cost convective assembly process. The structure formed by an uncontrolled deposition method resulted in a nano-cluster morphology, which was annealed at various temperatures to tune the optical absorbance properties by transforming the nano-clusters to a nano-island morphology by modifying the structural shape and interparticle separation distances. The dependence of the size and the interparticle separation distance of the nano-islands on the LSPR properties were analyzed in the simulation. The effect of adsorption of protein layer on the nano-island structures was simulated and a relation between the thickness and the refractive index of the protein layer on the LSPR peak was presented. Further, the sensitivity of the gold nano-island integrated sensor against refractive index was computed and compared with the experimental results