Abstract: Lab-on-a-chip microfluidic devices having micro-channels able to withstand an internal channel pressure of more than 4,000 psi are described. The micro-channels have rounded cross-sections that prevent turbulent flow within a fluid conveyed within the channel. The channel may have serpentine-shaped length extending between a channel inlet and a channel outlet, the channel thereby being of sufficient length to observe both the stationary and moving phases of the fluid in a chip having a sufficiently small footprint that it is suitable for incorporation into a miniaturized spectrometer. Methods of fabricating lab-on-a-chip microfluidic devices are described by etching recesses in chip substrates such that a first substrate recess mirrors a second substrate recess in an opposed orientation, aligning the substrates such the recesses cooperatively define a micro-channel having a rounded cross-section, and bonding the substrates to define a smooth-walled micro-channel.