A study on bubble growth mechanisms and underlying physical phenomena of flow boiling in silicon nanowire (SiNW) microchannels has been performed and compared these results with plainwall microchannels. A new approach in studying bubble dynamics and forces acting on liquid-vapor (L-V) interface of growing bubble has been proposed based on theoretical, experimental and visual studies. Bubble size, liquid film thickness, interfacial properties are measured and L-V interfaces are detected from high speed visualization data and results are analyzed by vision-based approach. Force analysis during instantaneous bubble growth from bubble nucleation to formation of annular flow regime has been performed for both the SiNW and plainwall microchannel configurations. Results from force analysis show the dominance of surface tension at L-V interface of growing bubble which resulted higher heat transfer contact area, lower thermal resistance and higher thin film evaporation. Whereas, inertia force is dominant at L-V interface of fully grown bubble and it helps in bubble removal process and rewetting before flow reversal. Significant differences between SiNW and plainwall microchannels have been observed in bubble growth mechanism, heat transfer mode and forces acting on L-V interface.