PROCEEDINGS ARTICLE | February 25, 2009
Proc. SPIE. 7202, Laser-based Micro- and Nanopackaging and Assembly III
KEYWORDS: Fabrication, Refractive index, Microfluidics, Femtosecond phenomena, Waveguides, Interferometers, Sensors, Glasses, Laser induced fluorescence, Lab on a chip
A lab-on-a-chip (LOC) is a device that incorporates in a single substrate the functionalities of a biological laboratory, i.e.
a network of fluidic channels, reservoirs, valves, pumps and sensors, all with micrometer dimensions. Its main
advantages are the possibility of working with small samples quantities (from nano- to picoliters), high sensitivity, speed
of analysis and the possibility of measurement automation and standardization. They are becoming the most powerful
tools of analytical chemistry with a broad application in life sciences, biotechnology and drug development. The next
technological challenge of LOCs is direct on-chip integration of photonic functionalities for sensing of biomolecules
flowing in the microchannels. Ultrafast laser processing of the bulk of a dielectric material is a very flexible and simple
method to produce photonic devices inside microfluidic chips for capillary electrophoresis (CE) or chemical
microreactors. By taking advantage of the unique three-dimensional capabilities of this fabrication technique, more
complex functionalities, such as splitters or Mach-Zehnder interferometers, can be implemented. In this work we report
on the use of femtosecond laser pulses to fabricate photonic devices (as waveguides, splitters and interferometers) inside
commercial CE chips, without affecting the manufacturing procedure of the microfluidic part of the device. The
fabrication of single waveguides intersecting the channels allows one to perform absorption or Laser Induced
Fluorescence (LIF) sensing of the molecules separated inside the microchannels. Waveguide splitters are used for
multipoint excitation of the microfluidic channel for parallel or higher sensitivity measurements. Finally, Mach-Zehnder
interferometers are used for label-free sensing of the samples flowing in the microfluidic channels by means of refractive
index changes detection.
