This paper presents a design for a label free Si photonic wire "lab on a chip" arrayed biosensor with 8 sensing and 8 reference channels. It provides an advanced means for the label free detection of target molecules, for affinity binding analysis and for the time domain real-time monitoring and parallel detection of solutions, gases, or reactions near the sensing channel surface. The sensitivity of detection of the device is at the highest level among all the other methods, which is at least 10-100 times more sensitive than that of currently commercial available biosensor devices and instruments. The fabrication of the device is compatible with well-established semiconductor fabrication technologies. The device is able to be monolithically integrated with CMOS electronics, and combined with microfluidics.