## 4 Conclusions  
Electrically conductive TPU/GE porous structures were successfully fabricated by SLS processing by using a home-made powder realized by wrapping GE nanoplatelets onto TPU particles. Several 3D mathematically defined architectures with different porosity extents were designed and realized, namely Gyroid, Diamond, and Schwarz. Electrical and thermal conductivity, mechanical strength, filler dispersion, and interaction with the polymer matrix of the TPU/GE porous systems were investigated and correlated with their porosity and internal architecture.  
Morphological characterization clearly indicated that SLS manufacturing is suitable to create porous structures with narrow pore size distributions and high pore interconnectivity. Moreover, upon processing, the GE sheets remain entrapped in between the interparticle boundaries, thereby forming a segregated conductive network fully percolating the porous structure. GE hindered crystallization of TPU hard segments, but reduced the mobility of the polymer soft segments, increasing the \(T_{\text{g}}\). Furthermore, GE brought about an improvement of thermal stability of TPU. Compression tests revealed that S geometry provides the porous structure with a higher elastic modulus in comparison to the corresponding D and G geometries.  
All architectures showed electrical conductivity as well as negative piezoresistive behavior during cyclic compression tests, characterized by outstanding GF absolute values. In particular, S geometry structures yielded GF values of 12.4 at 8% strain, due to the combination of GE network segregation and higher size of trabeculae connecting the porosity. GF absolute values ranging from 60 to 20 were observed for deformation extents from 1% to 5%, demonstrating that the SLS-processed porous systems can be used in the detection of strains lower than 5%. Upon cyclic piezoresistive sensing tests, all samples exhibited excellent behavior repeatability, regardless of their porosity and geometry. Thermal conductivity of the TPU/GE structures significantly decreased with increasing porosity, while the effect of the structure architecture was less relevant.  
The reported results demonstrate that the TPU/GE powder is a suitable material for the SLS fabrication of porous structures with highly tailored flexibility and electrical conductivity. The powder enables the obtainment of a right balance between mechanical and functional properties of the printed structures, which in turns hold great potential to be used as flexible, highly sensitive, and stable piezoresistive sensors in wearable or implantable devices, and dielectric elastomer actuators.  
Conceptualization, M.L., L.A., and H.X.; methodology and sample preparation, A.R., G.F., and X.G.; data analysis, A.R., G.R., G.G.B., and C.S.; writing--original draft preparation, A.R., G.R., and P.C.; writing--review and editing, M.L., P.C., L.A., and H.X. This research was funded by Marie Sklodowska-Curie Actions (MSCA) Research and Innovation Staff Exchange (RISE) H2020-MSCA-RISE-2016, Project Acronym: Graphene 3D--Grant Number: 734164, and the National Key R&D Program of China (2017 YFE01115000). Thanks are due to [PERSON] (IPCB-CNR) for help in acquiring Raman spectra.  
The authors declare no conflict of interest.