**Acknowledgements**

**5.2. Technology for fabrication of nanofluidic channels**

(CMOS) technology [177, 178].

18 Microfluidics and Nanofluidics

nels may plug-up during bonding.

**5.3. Applications of nanofluidics**

capabilities.

**6. Conclusions**

According to the National **S**cience Foundation (NSF) in the US and its National Nanotechnology Initiative (NNI), nanotechnology involves *"the application of scientific knowledge to manipulate and control matter in the nanoscale"* [158, 170], more or less arbitrarily defined at ≤100 nm [158, 170]. Nanofluidics often falls under nano electro mechanical systems (NEMS) [164, 177–179, 184] typically fabricated using complementary metal oxide semiconductor

For nanofabrication, many technologies have been described [159–162, 165, 166, 169, 171, 172, 180]. Some of them are nano-specific [159, 169] for example, scanning probe lithography (SPL) [161], etching using a focused ion beam (FIB) [171] and nanoimprinting [159]. In many cases use of a cross-sectional area of a nanochannel is preferred (e.g., 10 nm by 10 nm) rather than aspect ratio. Nanofluidic channels can be nanofabricated using either top-down or bottom-up approaches.

**Top down methods of fabrication of nanochannels:** By analogy to micromachining, these fabrication methods include bulk nanomachining; surface nanomachining; and, imprinting (as is typical of soft-lithography) [159, 161–165, 169]. A top plate is typically used to cover nanochannels but due the nanosize of the channels and unless precautions are taken, chan-

**Bottom up methods of nanostructure formation:** in some cases molecules can be "convinced"

**Associated nanofabrication technologies** include scanning probe lithography (**SPL**) [161], electron beam lithography (EBL) [159] and dip-pen nanolithography [185]. Such approaches are typically used to bypass the diffraction-limit of photolithography or to provide new

In addition to enabling fundamental studies of fluid-flow and of transport phenomena (with many studies aimed at the study of naturally occurring processes in biological nanochannels), many applications are aimed at bio-sciences, bio-nano-technology and bio-analytical chemistry where applications exist in abundance [166–169]. Applications outside of classical nano-fluidics include nano-pores (e.g., for bio-applications and DNA sequencing) [186–192] and even for the study of fluid-flow in nano-porous media [193, 194]. For chemical analysis, NEMS have been developed for single protein mass spectrometry [174] and for airborne nanoparticle detection [176]. From this short list it can be concluded that nanofluidics has the

Microfluidics continues to receive attention in science and technology due to its many applications. And as shown, it has the potential to find applicability in constraining atmosphericpressure microplasmas in 2D-microfluidic channels (**Figures 8** and **10**) or in 3D-millifluidic

to self-assemble into nanostructures by controlling chemical conditions [160, 162].

potential to become a disruptive technology worthy of further investigation.

Financial assistance from NSERC (Natural Sciences and Engineering Research Council) of Canada is gratefully acknowledged. A special thank you to Professor (now Emeritus, ETH Zurich, Switzerland) Dr. Henry Baltes for the many enlightening discussions we had on MEMS and on miniaturization.
