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. 2019 Sep;370(3):555–569. doi: 10.1124/jpet.119.258707

Fig. 3.

Fig. 3.

Microneedle-coating methods that have been shown to selectively coat the microneedle shafts without contaminating the base substrate of the microneedle array. (A-i) Concept of dip coating microneedle shafts via a protective mask, (A-ii) mask with laser-drilled dip holes placed on top of an underlying coating channel, (A-iii) stereomicrograph of a stainless steel microneedle array coated with riboflavin using a mask that contained dip holes affixed over a solution reservoir (Gill and Prausnitz, 2007b), (B-i) concept of dip-coating microneedles via an additively manufactured solution-filled coating mask device (Caudill et al., 2018), (B-ii) polyethylene glycol dimethacrylate microneedles coated with fluorescently labeled bovine serum albumin (Caudill et al., 2018; on the left is a scanning electron micrograph and on the right is a confocal micrograph), (C-i) concept of generating a thin coating liquid film on a roller using a doctor blade (Ameri et al., 2010), (C-ii) scanning electron micrograph of titanium microneedles coated with parathyroid hormone peptide using the drum roller thin-film method (Ameri et al., 2010), (D-i) concept of generating a thin liquid film using a reservoir that has a shallow depth, (D-ii) micrographs of liquid crystal polymer microneedles coated with lidocaine (Zhang et al., 2012a), (D-iii) stereomicrograph of poly(l-lactide) microneedles coated with lidocaine containing sulforhodamine B as a colored dopant (Baek et al., 2017), (E-i) concept of using a microstructure– well to create a thin liquid film and dipping microneedles into it (Lee et al., 2017a), (E-ii) scanning electron micrograph of poly(l-lactide) microneedles coated with bleomycin after dipping into a liquid film created in a microstructure– well (Lee et al., 2017a), (F-i) a piezoelectric nozzle coating onto a microneedle array (Uddin et al., 2015), (F-ii) scanning electron micrograph of a stainless steel microneedle array coated with 5-fluororacil via piezoelectric-based inkjet printing (Uddin et al., 2015). Figures used with permission from publishers.