Microchip　capillary　electrophoresis　(MCE)　is　a　powerful　technique　for　rapid　separation;　however,　its　acceptance　in　routine　laboratories　is　still　limited.　Compromises　caused　by　the　efforts　for　solving　different　problems,　such　as　reducing　its　cost　of　fabrication　and　ensuring　high　separation　efficiency,　undermine　the　competitiveness　of　this　technology　compared　to　other　separation　techniques.　Contrary　to　the　conventional　pursuit　of　narrow　microchannels,　this　study　investigated　the　suitability　of　microchips　with　channels　at　the　sub-millimeter　level,　targeting　the　simplification　of　the　overall　operation,　cost　reduction,　and　robustness　improvement.　To　this　effect,　we　considered　the　influence　of　pressurized　flow　and　Joule　heating　on　the　separation.　The　suppression　of　pressurized　flow　with　viscous　solutions　was　confirmed　through　a　combination　of　simulations　and　experimental　results,　indicating　that　the　buffer　viscosity　was　enough　for　successful　separation.　We　fabricated　channels　of　200　mu　m　x　230　mu　m　using　computer　numerical　controlled　(CNC)　machining　and　obtained　theoretical　plate　numbers　of　4.8　x　10(5)　m(-1)　and　5.3　x　10(5)　m(-1)　for　fluorescein　isothiocyanate　(FITC)　labeled　small　molecules　and　DNA　fragments,　respectively,　with　a　buffer　viscosity　of　168　mPa　s　(0.5　%　hydroxypropyl　methylcellulose,　HPMC).　These　values　are　comparable　with　that　of　narrow-bore　microchips.　Furthermore,　we　did　not　observe　any　deleterious　effects　with　low-conductivity　buffers.　We　investigated　the　rapid　and　highly　sensitive　detection　of　mycoplasma　contamination　and　the　real　samples　of　circulating　cell-free　DNA　(cfDNA),　which　gave　a　limit　of　detection　(LOD)　as　low　as　2.3　ng　mL(-1).　Owing　to　the　significant　reduction　in　cost,　ease　of　operation,　and　fast　separation　capabilities　demonstrated　in　this　work,　MCE　can　be　a　viable　alternative　to　the　usual　slab　gel　electrophoresis　running　in　most　biological　laboratories.