NOVELTY - The method comprising: providing a printing apparatus (130) comprising an apparatus polarization area; providing a substrate (135) comprising a substrate polarization area; aligning the substrate on the printing apparatus such that the apparatus polarization area and the substrate polarization area overlap to form alignment area; generating polarized light by directing light at the alignment area; printing a pattern on the substrate using the printing apparatus; and monitoring at least one characteristic associated with the polarized light during the printing of the pattern.    USE - The method is useful for detecting substrate alignment during a printing process (claimed).    ADVANTAGE - The method is capable of continuously detecting the substrate alignment during the printing process with high detection sensitivity and reduced mechanical error.    DETAILED DESCRIPTION - The method comprising: providing a printing apparatus (130) comprising an apparatus polarization area; providing a substrate (135) comprising a substrate polarization area; aligning the substrate on the printing apparatus such that the apparatus polarization area and the substrate polarization area overlap to form alignment area; generating polarized light by directing light at the alignment area; printing a pattern on the substrate using the printing apparatus; and monitoring at least one characteristic associated with the polarized light during the printing of the pattern, where a variation in the characteristic is indicative of a misalignment between the substrate and the printing apparatus. The printing process is configured as a roll-to-roll printing process. The method further comprises: stopping the printing of the pattern responsive to determining that the substrate is not aligned on the printing apparatus; and adjusting a position of the substrate on the printing apparatus responsive to determining that the substrate is not aligned on the printing apparatus. The printing apparatus comprises a substrate holder having the apparatus polarization area, where the substrate holder holds the substrate during the printing process. The printing apparatus comprises a pattern roller (125) having the apparatus polarization area, where the pattern roller is configured to print the pattern on the substrate during printing. The printing apparatus is an inkjet printing apparatus, a screen printing apparatus, a nano-imprinting apparatus, a lithographic printing apparatus, an offset lithographic printing apparatus, a UV lithographic printing apparatus, a gravure printing apparatus, an offset gravure printing apparatus, and a flexographic printing apparatus. The characteristic comprises an intensity of the polarized light. The characteristic comprises polarization characteristic of the polarized light. The substrate polarization area is configured to polarize light through one of the following: polarization through reflection, polarization through refraction, and polarization through scattering. The apparatus polarization area is configured to polarize light through one of the following: polarization through reflection, polarization through refraction, and polarization through scattering. The light directed at the alignment area has an intensity of about 20 candelas. The pattern comprises at an electronic element including an electronic wiring, a conductor, a resistor, a dielectric, an inductor, a diffractive optic element, a light guide, an optical ROM, a diode, a transistor, an LED, a solar cell, a sensor, an indicator, an organic LED, organic transistor circuits, multilayer electronic circuits, memory device, a solar cell, a miniaturized fuel cell, an optical waveguide, an optical microelectromechanical systems array, an organic read-only memory element, an organic FET, an electronic circuit, a radio-frequency identification element, an electronic circuit for a sensor, a biocompatible electronic element, a battery including thin-film battery, a display, a display active matrix backplane, a nanoscale photovoltaic element, a radio- frequency identification tag, a capacitor and a resistor. The substrate polarization area is configured as a strip arranged at an edge of the substrate. INDEPENDENT CLAIMS are included for:    (1) a printing apparatus configured to detect substrate alignment during printing; and    (2) a method for manufacturing a printing apparatus.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic view of a printing system.    Printing system (100)    Ink (110)    Pattern roller (125)    Printing apparatus (130)    Substrate. (135)