Research Article Received: 5 September 2012 Revised: 8 February 2013 Accepted: 22 February 2013 Published online in Wiley Online Library: (wileyonlinelibrary.com) DOI 10.1002/pi.4509 Melt electrospinning writing of three-dimensional star poly(ε -caprolactone) scaffolds Carlos Mota, a Dario Puppi, a Matteo Gazzarri, a Paulo B ´ artolo b and Federica Chiellini a∗ Abstract In the last decade, the melt-electrospinning technique has gained attention for the production of highly porous microfibrous tissue engineering scaffolds. The possibility of processing polymers without the use of organic solvents is one of the main advantages over solution electrospinning. In this study, computer-controlled melt-electrospinning of a commercial poly(ε- caprolactone) and of two batches with different molecular weights of a three-arm star poly(ε-caprolactone) by means of a screw-extruder-based additive manufacturing system is reported. Experimental parameters such as processing temperature, extrusion flow rate and applied voltage were studied and optimized in order to obtain non-woven meshes with uniform fibre morphology. Applying the optimized parameters, three-dimensional scaffolds were produced using a layer-by-layer approach (0 − 90 ◦ lay-down pattern). c  2013 Society of Chemical Industry Keywords: tissue engineering; scaffold; melt-electrospinning; additive manufacturing; poly(ε-caprolactone); star polymers INTRODUCTION The possibility of producing polymeric fibres with a diameter in the micro-size range by processing a polymer melt (thus avoiding the use of organic solvents) makes melt-electrospinning (melt-ES) a technique suitable for different tissue engineering applications. 1 Moreover, the lower packing density of melt- electrospun meshes compared with nanofibre meshes obtained by solution electrospinning (sol-ES) allows enhanced cell migration to be achieved which can lead to colonization throughout the whole tissue engineered construct. 2 However, achieving melt- electrospun nanofibres is still a challenge. 3,4 Reduced bending instabilities of the polymer melt jet in the electric field, compared with sol-ES, leads to the production of relatively large fibre diameter and small fibre collection area. As described in the literature, this phenomenon can be related to the high viscosity and the fast solidification of the polymer melt in the spinning region 5 – 8 and can be favourable for the production of patterned meshes. 9 The direct writing technique indeed allows for the production of melt- electrospun scaffolds with controllable architectures employing an additive manufacturing (AM) approach, as recently demonstrated by Brown et al. 10,11 AM techniques (also known as solid free-form fabrication techniques) involve the layer-by-layer building of porous structures from three-dimensional (3D) model data. 12 In comparison with other techniques employed for scaffold fabrication, they allow better control over scaffold internal architecture and external geometry. A considerable amount of literature has been published on the fabrication of tissue engineering scaffolds by means of AM techniques based on different approaches, such as systems based on laser or UV light sources 12,13 and systems based on extrusion of a polymer melt 14 or solution. 15 Poly(ε-caprolactone) (PCL) is a semicrystalline polymer widely investigated in the biomaterials field due its well-assessed biocompatibility and biodegradability as well as good rheological and viscoelastic properties. 16 The relatively low melting temperature and high thermal stability make it a good candidate for melt-ES to produce micro-sized fibrous meshes suitable for tissue engineering purposes. 10,11,17 PCL-based blends and copolymers have also been investigated for melt-ES in order to improve material processing properties, such as viscosity at low temperatures, and to reduce production costs and thermal degradation risks. 1,7,17,18 Star polymers are made up of linear polymeric chains attached to a relatively small central moiety. Due to their small size, spherical structure and limited interaction between molecules, star polymers have unique properties compared with in particular linear polymers with equivalent molecular weight. Their compact 3D macromolecular structure can offer advantages over their ∗ Correspondence to: Federica Chiellini, BIOLab, Department of Chemistry and Industrial Chemistry, University of Pisa, Pisa, Italy. E-mail: federica@dcci.unipi.it a Laboratory of Bioactive Polymeric Materials for Biomedical and Environmental Applications (BIOLab), Department of Chemistry and Industrial Chemistry, University of Pisa, via Vecchia Livornese 1291, 56010, San Piero a Grado (Pi), Italy b Centre for Rapid and Sustainable Product Development, Centro Empresarial da Marinha Grande, Rua de Portugal − Zona Industrial, 2430-028, Marinha Grande, Portugal Polym Int (2013) www.soci.org c  2013 Society of Chemical Industry