We examine various microfluidic channel designs for sample delivery to silicon nano-wire biosensors pertaining to the modeling and simulation. Nano-wires with its high sensitivity permits label free detection of bio-molecules. Without careful considerations to its fluidic delivery network, effects of detection can be limited. Different micro-channel designs of relatively larger width aid in fluid release and sensors are placed strategically to attain high efficiency in bio-sample delivery. One design establishes the viability of hydrodynamic focusing through splitting a single flow into two and permits focusing of bio-samples at the flow recombination region. It avoids the delicated fluidic delivery systems generally used in hydrodynamic focusing. A focusing effect of 71.3% based on the movement of a massless particle in the fluid is achieved using a straight channel design with a partition wall inside. Moreover, sample is focused in low velocity region which maintains minimal impact to nanowire sensor. This provides a simple and efficient delivery system for the nano-wire sensor upon integration. © 2006 IOP Publishing Ltd.