Low-power　CO2　laser　direct-writing　ablation　was　used　to　micromachine　a　microchannel　on　the　polycarbonate　substrate　in　this　work.　The　influence　of　the　process　parameters　(the　laser　power,　the　moving　velocity　of　the　laser　beam　and　the　scanning　times)　on　the　micromachining　quality　(the　depth,　the　width　and　their　aspect　ratio)　of　the　microchannel　was　experimentally　studied.　The　depth　and　width　of　microchannel　both　increase　with　the　increase　of　the　laser　power　and　the　decrease　of　the　moving　velocity　of　the　laser　beam.　When　higher　laser　power　and　slower　moving　velocity　were　used,　the　polycarbonate　surface　bore　more　heat　irradiated　from　the　CO2　laser　for　longer　time　which　results　in　the　formation　of　deeper　and　wider　molten　pool,　hence　the　ability　to　fabricate　bigger　microchannel.　Because　of　the　effect　of　the　laser　power　on　the　depth　and　width　of　microchannels,　higher　aspect　(depth/width)　ratio　could　be　achieved　using　slower　moving　velocity　and　higher　laser　power,　and　it　would　reach　a　steady　state　when　the　laser　power　increases　to　9.0W　possibly　caused　by　the　effect　of　laser　power　on　the　different　directions　of　microchannel.　The　polycarbonate-polycarbonate　chip　was　bonded　with　hot-press　bonding　technique.　(C)　2008　Elsevier　Ltd.　All　rights　reserved.