Quantitative detection of multiple biomolecules, such as DNA and proteins, in a high-throughput manner is required for diagnostics of complex diseases such as cancer as well as for drug discovery and fundamental scientific knowledge of molecular signaling pathways. We have developed a microfluidic chip with multiple microchannels to study biomolecular reactions and realize multi-target biosensing based on molecular nanomechanics. In particular, biological reactions on one surface of a microcantilever beam change its surface tension due to intermolecular energetic and entropic interactions, which generate sufficient torque to bend the cantilever beam. Integration of multiple microchannels allows separate functionalization of each cantilever so that simultaneous detections of multiple analytes can be accomplished. By using the chip, microfluidics can be investigated to understand how the mass transfer rate of the analyte to the surface compares with the biological reaction rate on the surface. Parameters such as analyte and ion concentration of the buffer solution, which have been observed to affect the beam deflection, can also be studied to see how they affect the mass transfer rate to the reaction surface. The biomolecular device containing both microchannels and cantilevers will give us a better understanding of mass transfer in biomolecular reactive flows so that one should be able to optimize the experiment of biomolecule detection based on this technique.