In order to solve the drawbacks of sensitivity and portability in optical biosensors we have developed ultrasensitive and miniaturized photonic silicon sensors able to be integrated in a "lab-on-a-chip" microsystem platform. The sensors are integrated Mach-Zehnder interferometers based on TIR optical waveguides (Si/SiO2/Si3N4) of micro/nanodimensions. We have applied this biosensor for DNA testing and for detection of single nucleotide polymorphisms at BRCA-1 gene, involved in breast cancer development, without target labeling. The oligonucleotide probe is immobilized by covalent attachment to the sensor surface through silanization procedures. The hybridization was performed for different DNA target concentrations showing a lowest detection limit at 10 pM. Additionally, we have detected the hybridization of different concentrations of DNA target with two mismatching bases corresponding to a mutation of the BRCA-1 gene. Following the way of the lab-on-a-chip microsystem, integration with the microfluidics has been achieved by using a novel fabrication method of 3-D embedded microchannels using the polymer SU-8 as structural material. The optofluidic chip shows good performances for biosensing.
This paper describes the fabrication, packaging and characterization of novel multilayer polymer microfluidic systems fabricated by a CMOS compatible process. These microfluidic devices were specially designed for BioMOEMS applications. Embedded multilayer rectangular smooth and uniform microchannels, 50 to 150 mm wide and 18mm deep were studied. Steady-state flow rates and pressure driven flow control were measured in the laminar flow regime. Flow rates ranging from 1 to 100 μl/min, at pressure drop ranging from 10 to 600 kPa, were obtained. These flow rates yield Reynolds numbers (Re) up to 20. Results indicate that the experimental Re and the flow friction coefficient (f) are in good agreement with the laminar flow theory. These experimental results facilitate the future designs of different microfluidic devices designed by using classical fluidic theory.
We also present two different methods developed for macro/microfluidic packaging in order to connect these microfluidic devices to the macroscopic world. The microsystem packaging can withstand pressure drops up from 500 to 2000 kPa with any liquid leakage.
We show the design, fabrication and testing of micro/nanobiosensor devices based on optical waveguides in a highly sensitive interferometric configuration and by using evanescent wave detection. The devices are fabricated by standard Silicon CMOS microelectronics technology after a precise design for achieving a high sensitivity for biosensing applications. Two integrated Mach-Zehnder interferometric (MZI) devices, using two technologies, have been developed: (a) a MZI Microdevice based on ARROW waveguide (b) a MZI Nanodevice based on TIR waveguide. Direct biosensing with both sensors has been tested, after a specific receptor coupling to the surface device using nanometer scale immobilization techniques. Further integration of the microoptical sensors, the microfluidics, the photodetectors and the CMOS electronics will render in a lab-on-a-chip microsystem.
This article describes a novel low temperature full wafer adhesive bonding process to fabricate three-dimensional (3-D) embedded microchannels using SU-8 photoresist as structural material.
The technology development includes an improvement of the SU-8 photolithography process in order to produce high uniformity films using Taguchi methodology. After that, 3-D embedded microchannels are fabricated by a low temperature adhesive bonding of the the SU-8 thick-films. The process parameters have been chosen in order to achieve a strong and void-free bond. Different examples using this new technology are shown, including bonding between Silicon, Pyrex and combinations of them, in order to obtain 3-D interconnected microchannels between the wafers. Microchannels with vertical smooth walls and aspect ratios up to five have been obtained. Channels depth from 40 to 60 μm and 10 to 250 μm width have been achieved. Liquid has been introduced into the channels verifying a good sealing of the 3-D microchannels. The fabrication procedure described in this article is fast, reproducible, CMOS compatible and easily implemented using standard photolithography and bonding equipment.