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Listeria monocytogenes is one of the most common causes of food illness deaths worldwide, with multiple outbreaks in the United States alone. Current methods to detect foodborne pathogens are laborious and can take several hours to days to produce results. Thus, faster techniques are needed to detect bacteria within the same reliability level as traditional techniques. This study reports on a rapid, accurate, and sensitive aptamer biosensor device for Listeria spp. detection based on platinum interdigitated array microelectrodes (Pt-IDEs). Pt-IDEs with different geometric electrode gaps were fabricated by lithographic techniques and characterized by cyclic voltammetric (CV), electrochemical impedance spectroscopy (EIS), and potential amperometry (DCPA) measurements of reversible redox species. Based on these results, 50 μm Pt-IDE was chosen to further functionalize with a Listeria monocytogenes DNA aptamer selective to the cell surface protein internalin A, via metal-thiol self-assembly at the 5' end of the 47-mer's. EIS analysis was used to detect Listeria spp. without the need for label amplification and pre-concentration steps. The optimized aptamer concentration of 800 nM was selected to capture the bacteria through internalin A binding and the aptamer hairpin structure near the 3' end. The aptasensor was capable of detecting a wide range of bacteria concentration from 10 to 106 CFU/mL at lower detection limit of 5.39 ± 0.21 CFU/mL with sensitivity of 268.1 ± 25.40 (Ohms/log [CFU/mL]) in 17 min. The aptamer based biosensor offers a portable, rapid and sensitive alternative for food safety applications with one of the lowest detection limits reported to date.

We present research results centered on development of a highly sensitive handheld chem/biosensor device using a novel class of engineered proteins, designed to undergo extreme conformational changes upon binding their target, which in turn cause extreme changes in refractive index in the protein layer. These proteins are attached to a detector chip with a structured metasurface, to translate the refractive index change into an enhanced shift in surface plasmon resonances (SPR), thereby improving the sensitivity of the overall detector relatively to current commercially available SPR systems. Theoretical calculations have demonstrated the potential of the conformational changes in the engineered proteins to provide the desired change in refractive index. A plasmonic chip with a simple grating metasurface structure was designed to maximize the SPR shift. A prototype chip and a prototype for the overall device housing were fabricated with the inclusion of all other required (commercially available) optical components. The proposed device holds considerable promise as a low-cost, highly sensitive, field-deployable detection system for chemical and biological toxins.

A silicon-based athermal double-ring resonator biosensor with a vertically coupled configuration is developed. We present an optimal design of the sensor structure by specifying the radii of the reference and the sensing rings, the vertical coupling offset, d, between the two rings and the bus waveguide, and the lateral offset, l, between the edges of the rings and the bus waveguide. By using Lumerical software package, we demonstrate that the optimal vertical and lateral offsets are d=325 nm and l=-80 nm, respectively. One major challenge faced by ring based biosensors is their temperature dependent characteristics. In this study, the sensing ring is exposed to the biomaterial under test, while the reference ring provides a temperature-insensitive reference to the sensing measurements. By assuming the biomaterial medium has small variations in temperature, we conclude that the proposed biosensor device offers temperature insensitive measurement, where the temperature effects are fully corrected by the reference ring response. The double-ring sensors are proposed to be fabricated with the local oxidation of silicon process, without the need for advanced lithography methods such as e-beam or deep UV lithography. In addition, the vertically coupled double-ring configuration allows precise control of the critical coupling separation between the rings and the bus waveguide. The proposed silicon double-ring biosensor can be used for highly sensitive and stable sensing for both biomedical and environmental applications.

Bio-security for health monitoring and diagnosis are the needs of the hour, for rapid detection of biological and chemical species. This calls for a necessity to develop a cost effective miniaturized and portable biosensor device for in-situ biomedical applications and Point-of-Care Testing (POCT). While portability of the biosensor is required for in-situ medical detections, miniaturization is essential for handling smaller sample volumes and high throughput. Thus, the above mentioned concerns cannot be addressed unless a fully integrated biosensor system is developed. In this work, an integrated opto microfluidic based Lab-on-a-chip device is proposed for carrying out fluorescence based biodetection. The input and output fibers were integrated with the microfluidic channel so as to make a robust setup. Fluorescence detection was carried out using Alexafluor 647 tagged antibody particles and the output was measured with a Spectrometer-on-Chip, integrated with the device. The experimental results prove that the proposed device is highly suitable for Lab-on-a-Chip applications.

This paper deals with the generation, measurement and control of micro liquid droplet jet in water. In connection with the development of a lipid membrane biosensor device for underground water pollution, a method of working liquid transportation by micro droplet jet has been proposed. The generation and the behavior of micro droplet jet have been investigated by the method of flow visualization. Experimental results show that the behavior of micro droplet is controllable by changing the driven pressure and the duration time of jet ejection. It is feasible to transport the working liquid to a given place by arranging the relative position according to the trajectory of droplet jet.