An apparatus comprising: a microneedle assembly comprising a base surface, a plurality of microneedles extending outwardly from the base surface, and a pathway at least partially defined by a microneedle of the microneedle assembly; and a membrane draped over at least a portion of the plurality of microneedles, the membrane comprising: an elongate aperture that is open along a length of the pathway so that the elongate aperture is in fluid communication with the pathway, wherein said elongate aperture has a length and a width, the length being greater than the width, an outer portion in opposing face-to-face contact with at least an outer portion of the microneedle, and an inner portion facing toward at least a portion of the base surface, wherein at least a portion of the membrane is spaced apart from the microneedle so that a gap is defined between the membrane and the microneedle; the gap extends both at least partially around the microneedle and at least partially along the microneedle; the membrane defines a pleat extending between the inner and outer portions (30, 32) of the membrane, and the pleat is positioned relative to the elongated aperture to control the size of the elongate aperture and the size and shape of the gap. a microneedle assembly comprising a base surface, a plurality of microneedles extending outwardly from the base surface, and a pathway at least partially defined by a microneedle of the microneedle assembly; and a membrane draped over at least a portion of the plurality of microneedles, the membrane comprising: an elongate aperture that is open along a length of the pathway so that the elongate aperture is in fluid communication with the pathway, wherein said elongate aperture has a length and a width, the length being greater than the width, an outer portion in opposing face-to-face contact with at least an outer portion of the microneedle, and an inner portion facing toward at least a portion of the base surface, wherein at least a portion of the membrane is spaced apart from the microneedle so that a gap is defined between the membrane and the microneedle; the gap extends both at least partially around the microneedle and at least partially along the microneedle; the membrane defines a pleat extending between the inner and outer portions (30, 32) of the membrane, and the pleat is positioned relative to the elongated aperture to control the size of the elongate aperture and the size and shape of the gap. an elongate aperture that is open along a length of the pathway so that the elongate aperture is in fluid communication with the pathway, wherein said elongate aperture has a length and a width, the length being greater than the width, an outer portion in opposing face-to-face contact with at least an outer portion of the microneedle, and an inner portion facing toward at least a portion of the base surface, wherein at least a portion of the membrane is spaced apart from the microneedle so that a gap is defined between the membrane and the microneedle; the gap extends both at least partially around the microneedle and at least partially along the microneedle; the membrane defines a pleat extending between the inner and outer portions (30, 32) of the membrane, and the pleat is positioned relative to the elongated aperture to control the size of the elongate aperture and the size and shape of the gap.