A smart applicator for liquid cosmetic to hair, skin or nails is described, comprising a position indicator to measure the relative change of position of the applicator across a nearly flat surface； a sensor array to measure the prior color or cosmetic condition of hair strands or skin condition； an optional comb array to direct hair strands from their roots into a regular linear array； a microcontroller which outputs electrical signals to operate an array of micro-mechanical or inkjet nozzles aligned with the comb array so as to dispense dye or cosmetic droplets to the hair strands or skin surface according to input received from said sensors.
