Microbiochips monolithically integrated with microfluidics, micromechanics, photonics, and electronics by 3D femtosecond laser direct writing

Microbiochips such as lab-on-a-chip (LOC) devices and micro totalanalysis systems (μ-TAS) can be regarded conceptually as a biologicalequivalent of conventional silicon integrated circuits, which involveminiaturization and integration of electronics. As its name implies, anideal LOC should have a very small footprint and yet still be capable offunctioning as a laboratory in which partial or complete chemical orbiological analysis can be performed automatically. A planar silicon chipthat integrates only microelectronics is clearly far from adequate for such a purpose, and other functional components such as microfluidics,microoptics, and micromechanics need to be incorporated into a chip with3D configurations. This poses a formidable challenge, because currentmainstream microfabrication technologies mostly rely on opticallithography, which is essentially a surface structuring technology.Recently, femtosecond laser direct writing has exhibited great potentialfor producing a variety of true 3D microstructures in various transparentmaterials. This is enabled by the nonlinear interaction between the tightlyfocused femtosecond laser beam and the material that is transparent to thelaser beam, since the interaction can be effectively confined to thevicinity of focal point where the laser intensity exceeds the threshold formultiphoton absorption. In this chapter, we provide an overview of 3Dfemtosecond laser direct writing technology and highlight its potential forfabrication of complex smart microsystems by furnishing some examplesof fabrication and hybrid integration of microfluidics, micromechanics,photonics, and electronics. In addition, application of some of ourmicrofluidic chips to biological research has resulted in new insights intovarious biological behaviors such the dynamics and functions ofmicroorganisms. Possible solutions for overcoming remaining challengesare discussed in the hope that this technology will provide amanufacturing solution for the emerging LOC industry.