The search for a cost-effective fabrication method for cross-linked polydimethylsiloxane (PDMS) based microreactors remains an attractive area of research. In this work, a simple and cost-effective method for fabricating microchannel with different geometrical configurations such as straight, helical and straight channel with gradual 90 degrees bend has been offered. In order to construct the microchannels slender copper wire of 0.21mm diameter has been planted inside a block of PDMS and then it has been easily drawn out by applying a little tensile force. Two different types of inlet sections (L and T types) have been constructed for each type of microchannel. Moreover, detailed flow visualization studies (flow patterns) using a biphasic system, toluene-wateracetic acid have been performed for straight and helical microchannels for mass transfer application. The flow patterns have been observed by varying a wide range of inlet velocities of both the phases from 0.0079 to 0.047 m/s. The effect of surface and viscous forces are dominant over other forces such as inertia and gravity, which is evident from the range of slug flow in both the microchannels. The overall volumetric mass transfer coefficient is found to be in the range of 0.06-0.6 s(-1), which is significantly higher than the reported results. This copper wire-based non-lithographic technique is flexible and convenient in comparison with conventional lithographic methods and may enable the production of miniature components for chemical and biochemical systems, involving continuous flow systems usually comprising of two or more phases.