A method of detecting contact of a micro-structural fluid ejector to a substrate, comprising the steps of: positioning the substrate on a substrate stage; providing a print head comprising the micro-structural fluid ejector, the micro-structural fluid ejector comprising: an output portion comprising an exit orifice having an output inner diameter, an input portion having a input inner diameter that is greater than the output inner diameter by a factor of at least 100, and a tapering portion between the input portion and the output portion; installing the print head above the substrate, the micro-structural fluid ejector being oriented with the exit orifice pointing downward; providing an imaging system comprising a camera, the tapering portion being located within a field-of-view of the camera; providing a print head positioning system which controls a vertical displacement and a lateral displacement of the print head and of the camera relative to the substrate; operating the imaging system; if a previous length is empty, or if the previous length is not empty but the current length is not greater than a sum of the previous length and a minimum length difference, then retaining the current length as the previous length, lowering the print head toward the substrate by a vertical distance, and repeating the step of operating the imaging system; and if the previous length is not empty and the current length is greater than the sum, determining that the micro-structural fluid ejector and substrate are in contact; wherein the step of operating the imaging system comprises the steps of: capturing a digital image of the tapering portion and its surroundings; pre-processing the digital image to detect edges; and analyzing the digital image in a region of interest where the tapering portion and its reflection should be present to calculate the current length, the current length being defined as a length of a longest contiguous one of the detected edges intersecting a top edge of the region of interest. positioning the substrate on a substrate stage; providing a print head comprising the micro-structural fluid ejector, the micro-structural fluid ejector comprising: an output portion comprising an exit orifice having an output inner diameter, an input portion having a input inner diameter that is greater than the output inner diameter by a factor of at least 100, and a tapering portion between the input portion and the output portion; installing the print head above the substrate, the micro-structural fluid ejector being oriented with the exit orifice pointing downward; providing an imaging system comprising a camera, the tapering portion being located within a field-of-view of the camera; providing a print head positioning system which controls a vertical displacement and a lateral displacement of the print head and of the camera relative to the substrate; operating the imaging system; if a previous length is empty, or if the previous length is not empty but the current length is not greater than a sum of the previous length and a minimum length difference, then retaining the current length as the previous length, lowering the print head toward the substrate by a vertical distance, and repeating the step of operating the imaging system; and if the previous length is not empty and the current length is greater than the sum, determining that the micro-structural fluid ejector and substrate are in contact; wherein the step of operating the imaging system comprises the steps of: capturing a digital image of the tapering portion and its surroundings; pre-processing the digital image to detect edges; and analyzing the digital image in a region of interest where the tapering portion and its reflection should be present to calculate the current length, the current length being defined as a length of a longest contiguous one of the detected edges intersecting a top edge of the region of interest. capturing a digital image of the tapering portion and its surroundings; pre-processing the digital image to detect edges; and analyzing the digital image in a region of interest where the tapering portion and its reflection should be present to calculate the current length, the current length being defined as a length of a longest contiguous one of the detected edges intersecting a top edge of the region of interest.