Active micromixer platform based on Lorentz force for lab-on-a-chip application.

Mixing in an active micromixer was achieved using Lorentz force-assisted actuation of an enameled copper wire. A single-step template-assisted soft lithography technique was used to construct the mixing chamber. The chamber had a volume of 1.86 µl. The application of a square wave alternating current in tandem with tension in the wire provided the necessary conditions for the resonant oscillation frequency of the wire. The repeatability of the ratio of higher harmonics to the fundamental frequencies of the oscillating wire conforms to standardization of the device fabrication, assembly, and functionality. Simulations and experiments were performed to validate uniform temperature distribution in the mixing chamber. Real-time optical detection of the sample assisted in sensing the completion of chemical reactions in the chamber. Mixing of various aqueous based chemical reactions was performed. It was found that mixing efficiency was greater than 95 percent. Multiple devices were fabricated to show the usability and reproducibility of the system.

Multiplexed detection of waterborne pathogens in circular microfluidics.

Microfluidic lab-on-a-chip presents an ideal solution for bacterial sensing and identification due to its advantages like large surface-to-volume ratio, requirement of low sample volume and multiplexing possibility. The present work deals with the development of an immunosensor chip using circular microchannels fabricated directly with microdimensional copper wire and permanent magnet for capture of Fe(3)O(4) magnetic nanoparticle (MNP) conjugate. The MNP facilitate capture of the antigen in a confined space and hence, enhanced fluorescence signal for detection. The multiplexed microfluidic chip permits visual detection and quantification of waterborne pathogens viz. Escherichia coli and Salmonella typhimurium simultaneously. CdTe quantum dots (QDs) with different emission wavelengths were conjugated with anti-E. coli and anti-S. typhimurium antibodies for concurrent fluorescence detection. The present technique provides an inexpensive yet powerful tool to image and quantify pathogens at low numbers with passage of large sample volumes.

Quantum dot based immunosensor using 3D circular microchannels fabricated in PDMS.

Microchannel is basic functional component of microfluidic chip and every step-forward of its construction technique has been receiving concern all over the world. The present work describes a novel, rapid and simple fabrication technique for building 3D microchannels in poly(dimethyl siloxane) (PDMS) elastomer. These microchannels were used for rapid detection of antigens (E. coli) by quantum dot (QD) based approach. Luminescent QD (CdTe) were synthesized by aqueous method and characterized using high resolution transmission electron microscopy (HRTEM), fluorescence spectroscopy and X-ray diffraction (XRD). The QDs were functionalized with anti-E. coli antibodies for immuno-detection. The reported process allowed easier and faster method of fabrication of circular 3D micochannels and demonstrated their potential use in an immuno-biosensor device.