Abstract: A biosensors and a method of forming a probe on a solid surface of a biosensor are disclosed and the method includes the following steps. A unit (a nucleotide or an amino acid) capped with a protecting group is covalently bonded on the solid surface of one of a plurality of sensor cells of the biosensor. At least one cycle of the following steps is performed until a desired number of units is formed: irradiating the one of the plurality of sensor cells, so as to remove the protecting group of the unit; and binding a unit capped with the protecting group to the de-protected unit. The one of the plurality of sensor cells is irradiated to remove the protecting group.