Under　pressure-driven　conditions　of　gas,　the　bubble　size　was　experimentally　studied　in　different　types　of　T-junction　microchannels　having　widths　of　300　mu　m　and　heights　of　100　mu　m.　The　bubble　length　increases　with　the　flow　rate,　and　we　observed　that　it　also　increased　with　the　driving　pressure.　This　was　proved　through　the　published　formulas　for　the　bubble　flow　pressure　difference　using　the　experimental　results.　Three　types　of　downstream　channels-normal,　movable,　and　deformed　walls　(of　different　lengths)-were　used　to　study　emerging　bubbles,　and　a　nonlinear　relationship　was　observed　between　them.　The　channel　type　directly　influenced　the　bubble　size　by　affecting　the　resistance　of　the　channel　with　bubbles.　Furthermore,　the　difference　between　the　resistances　of　a　normal　channel　and　a　deformed　channel　with　the　same　typical　dimension　was　determined　using　a　comparator　structure　between　two　parallel　channels　to　evaluate　the　effect　of　flow　resistance　on　bubble　generation.　The　adjustment　of　the　flow　rate　at　downstream　will　give　feedback　to　the　bubble　generation　in　the　double　T-junction　channel.　(C)　2021　Elsevier　Ltd.　All　rights　reserved.