# Influence of DMSO Non-Toxic Solvent on the Mechanical and Chemical Properties of a PVDF Thin Film  
[PERSON]  
1 Associated Laboratory of Energy, Transports and Aeronautics (LAETA), Biomechanic and Health Unity (UBS), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), 4200-465 Porto, Portugal, [EMAIL_ADDRESS] (A.D.A.) [PERSON]  
1 Associated Laboratory of Energy, Transports and Aeronautics (LAETA), Biomechanic and Health Unity (UBS), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), 4200-465 Porto, Portugal, [EMAIL_ADDRESS] (A.D.A.) [PERSON]  
1 Associated Laboratory of Energy, Transports and Aeronautics (LAETA), Biomechanic and Health Unity (UBS), Institute of Science and Innovation in Mechanical and Industrial Engineering (INEGI), 4200-465 Porto, Portugal, [EMAIL_ADDRESS] (A.D.A.) Footnote 1: email: {}  
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relevant properties of PVDF are a large dielectric constant of 10 (\(\epsilon\)) [29], high polarity, ionic conductivity of around 10\({}^{-4}\) S/cm at 20 \({}^{\circ}\)C [30], high piezoelectric coefficient of 49.6 pm/V [31] and high mechanical strength ([PERSON]'s modulus \(\approx\) 1.6 GPa and yield strength \(\approx\) 45 MPa [32]). Chemically, there is evidence of at least five polymorphic modifications in its structure (\(\alpha\), \(\beta\), \(\gamma\), \(\delta\) and \(\epsilon\)), with each phase being responsible for different behaviours in the material, caused by intrinsic properties. For example, \(\beta\) and \(\gamma\) phases are the most desirable when the goal is to use PVDF as a sensor or soft actuator due to their piezoelectric, pyroelectric and ferroelectric abilities [33; 34]. These phases, mainly the \(\beta\) phase, can be promoted using different methodologies, including mechanical stretching of \(\alpha\) phase [35], melting PVDF under specific and controlled conditions (i.e., high pressure) [36], applying an external electrical field [37], using ultra-fast cooling [38], solution crystallization at temperatures below 70 \({}^{\circ}\)C [39] or by addition of nucleating fillers (e.g., ionic liquids (ILs)). The inclusion of ILs (typically composed of an organic cation and an organic/inorganic anion) brings other advantages, such as lower actuation voltage and improvement to electromechanical stability and durability, leading to higher material performance [32]. Moreover, some solvents, such as dimethyl formamide (DMF), dimethylacetamide (DMAC) and dimethylsulfoxide (DMSO) can also play a role in \(\beta\) phase formation [40], since higher dipole moments tend to favour the formation of phases with piezoelectric properties [41]. Several authors have studied this polymeric material for many applications with different purposes [42]. For example, [PERSON] et al. [43] used PVDF with polyethylene glycol dissolved in DMAC to improve the process of water treatment. In the field of medicine, [PERSON] et al. [44] used PVDF films as the sensory component in a sensor system to monitor breathing and heartbeats during sleep. Moreover, PVDF has already been investigated as an energy harvester by [PERSON] et al. [45]. They proposed a design that uses a PVDF film to capture energy from bending as a power source for pacemakers. Focusing on PVDF's properties, [PERSON] et al. [32; 46] have studied the mechanical, chemical and electrical properties of PVDF-based materials with consideration of the inclusion of different ILs and using DMF as a solvent. Despite using different process techniques, both studies focus on the influence of different ILs on the properties of the material. All ILs increased the electroactive (EA) \(\beta\) phase content in proportion to the IL alkali chain length [32]. The degree of crystallinity (\(\chi\)) also increased [46] depending on the IL chain length, and the mechanical properties changed (plasticizing behaviour in the presence of the IL).