A novel approach to the manufacture of dissolving microneedles arrays using aerosol jet printing

Despite much research over the last few decades, microneedle arrays for the transdermal delivery of drugs have failed to live up to their initial promise. This may be changing however as companies close in on the commercial delivery of vaccines via this technology. These breakthroughs will undoubtably increase the interest in the use of microneedles arrays for the delivery of biopharmaceuticals but will also drive research into the development of scalable manufacturing processes for their fabrication. While 3D printing is an exciting development in this field, conventional Additive Manufacturing (AM) techniques are unsuitable for biopharmaceuticals due to the harsh processing conditions which can cause degradation of the active ingredient. In this paper we report the first use of Aerosol Jet Printing (AJP) as an AM technique for the fabrication of dissolving microneedle arrays. A formulation of poly(vinyl pyrrolidone), trehalose and glycerol dissolved in water was prepared and characterised. The formulation was aerosolised using ultrasonication and deposited onto a silicon substrate. Critical process parameters such as Computer Aided Design (CAD) design, flow rate, temperature, print speed and focussing ratio were studied to determine their impact on the microneedle quality attributes. 4 × 4 microneedle arrays were printed, with needle heights > 500 µm achieved with print times of 30 mins or less. The resulting needles had sufficient strength and sharpness to penetrate porcine skin samples. Importantly, the microneedles can be fabricated under benign conditions which should be suitable for the processing and subsequent delivery of biopharmaceuticals across the skin.