Although electrospinning is well-known to produce non-woven nanofibrous mats under the action of a high electric field, it is shown that by using synergistically the processes of electrospinning and electrospraying, it is possible to build well controlled 2D and even 3D micro-patterned composites. The building of such nanofibrous constructs is governed by the electric charge distribution accumulated at the surface of the material during the alternate deposition of electrospun nanofibers and electrosprayed microparticles thanks to an “electrostatic template assisted deposition” (ETAD).
Experimental investigations allowed the estimation of the amount of charges of the single electrospun jet as a function of the processing conditions. Furthermore, in the case of two simple collectors, i.e. a flat cylinder or a cylinder with grooves of adjustable width, the measurement of the voltage at the surface of the deposited fibers during electrospinning gave more insight into the local charges distribution as well as the kinetic of the charges release. These results allowed a deep understanding of the building of an “electrostatic template” over the electrospun fibers leading to precisely control the trajectory of the microparticles during the electrospraying step. The role of the properties (conductivity and amount of residual solvent) of the microparticles on the quality of the “electrostatic template” and thus on the control of the formation of patterned 2D and 3D nanofibrous composites was also investigated.
In order to apply the concept of ETAD process, several micropatterned substrates with different kinds of structures in height and characteristic lateral sizes ranging from few tens to few hundreds of microns were used as collectors. Then, electrospun fibers and electrosprayed microparticles were alternately deposited onto these collectors fixed on a rotary drum. Microstructured 2D bi-layer composites were obtained after an electrospinning step followed by an electrospraying step. Numerical simulations of this two-steps process were conducted and gave more insight into the mechanism of deposition. When electrospinning and electrospraying are carried out alternately, the electrostatic template effect is kept during the deposition steps and a 3D microstructured composite is obtained. Depending on the nature of the nanofibers and the microparticles, such 2D and 3D micropatterned materials can find applications in different fields such as biochips, biomimetic scaffolds or sensor applications.
 S. Nedjari, A. Hébraud, S. Eap, S. Siegwald, C. Mélart, N. Benkirane-Jessel, G. Schlatter, "Electrostatic Template-Assisted Deposition of Microparticles on Electrospun Nanofibers: Towards Microstructured Functional Biochips for Screening Applications", RSC Advances, vol. 5, pp. 83600-83607, 2015.
 Corinne R. Wittmer, Anne Hébraud, Salima Nedjari, Guy Schlatter, "Well-Organized 3D Nanofibrous Composite Constructs using Cooperative Effects between Electrospinning and Electrospraying", Polymer, vol. 55, pp. 5781-5787, 2014.
 A. Garcia Garcia, A. Hébraud, J-L. Duval, L. Gaut , C. Wittmer, D. Duprez, C. Egles, F. Bedoui, G. Schlatter, C. Legallais, "Poly(-caprolactone)/hydroxyapatite 3D honeycomb scaffolds for a cellular microenvironment adapted to maxillofacial-bone reconstruction", ACS Biomaterials Science and Engineering, vol. 4, pp. 3317–3326, 2018.