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Sacrificial Layer and Supporting Layer Techniques for the Fabrication of Ultra-Thin FreeStanding PEDOT:PSS Nanosheets Francesco Greco1, Alessandra Zucca1,2, Silvia Taccola1,2, Arianna Menciassi1,2, Paolo Dario1,2, and Virgilio Mattoli1 1 Center for MicroBioRobotics IIT@SSSA, Istituto Italiano di Tecnologia, Viale Rinaldo Piaggio 34, 56025 Pontedera, Italy 2 Biorobotics Institute, Scuola Superiore Sant’Anna, Polo Sant’Anna Valdera, Viale Rinaldo Piaggio 34, 56025 Pontedera, Italy ABSTRACT Aim of this work was to realize free-standing conductive nanofilms having very large surface area with typical nano-scale thickness (40-120 nm) by modifying existing approaches for nanostructured thin films assembly. We tested and optimized two different fabrication methods for the obtainment of free-standing conductive ultra-thin nanosheets based on the conductive polymer poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate) (PEDOT:PSS). Supporting Layer and Sacrificial Layer techniques permitted the obtainment of single layer nanofilms that can be released in water and of LbL multilayer nanosheets (PEDOT:PSS/Polyelectrolytes) that can be released in acetone, respectively. Here we describe the details of both the proposed fabrication methods and compare the properties of the realized nanosheets in terms of thickness, contact angle and conductivity. Interestingly, the realized free-standing nanosheets, despite their low thickness, are very robust and compliant while maintaining their structure and functionality. Possible applications are foreseen in the field of sensing and actuation, as well as in the biomedical field, e.g. as smart conductive substrates for cell culturing and stimulation. INTRODUCTION Ultra-thin polymeric films have been extensively studied also in the form of free-standing nanosheets, characterized by a very large surface area (up to tens of cm2) and by a thickness in the order of tens of nanometers [1]. Features such as biocompatibility, flexibility and the possibility to be functionalized make them attractive in the biomedical field [2]. Multilayered thin films are commonly fabricated by layer-by-layer (LbL) assembly technique [3]. While the use of LbL technique for obtaining polyelectrolyte multilayer structures [4] is particularly common, literature reports only one attempt to obtain free-standing conductive ultra thin films [5]. However, the proposed procedure is quite complex, involving many expensive, time consuming and delicate steps towards the obtainment of composite graphene/conductive polymer composite nanofilms. Only very recently a very innovative and easy method for the fabrication of conductive polymer free-standing nanofilms has been proposed by our group [6]. This technique allows to obtain conductive nanofilms that can be manipulated, folded and unfolded in water many times without suffering from cracks or from loss of conductive properties. In this paper we describe two different fabrication methods for the obtainment of freestanding conductive ultra-thin nanosheets based on the conductive