This paper is the first in a two-part study of the pressure-flow characteristics for a range of microchannels. Here, the manufacture of the channels and the resulting quality in terms of the channels' closeness to target dimensions, channel-to-channel variation for each sample, and the difference in area between the assumed perfect rectangular/trapezoidal shape of the channels and their actual cross-section are addressed. Wet etching with KOH produced trapezoidal channels 577 mum wide and 413 mum high. DRIE produced rectangular channels 304 mum wide and 332 mum high. Mechanical sawing produced near rectangular channels in both silicon and plastic. The silicon channels were 52 mum wide and 423 mum deep, and the plastic channels were 203 mum wide x 344 or 382 pm deep. Channel dimensions were measured using a scanning electron microscope. This paper demonstrates the feasibility of producing relatively large microchannels in two materials by three methods.