Effects of dual plasticizers for improved PVC gel-based varifocal tiny lens

Electroactive polyvinyl chloride (PVC) gel-based varifocal lenses are attractive due to their excellent transparency, simple fabrication, compact structure, and good flexibility. In this work, dibutyl adipate (DBA) and propylene carbonate (PC) were utilized to plasticize PVC for fabricating transparent, soft, and flexible gels by solvent casting method. The PVC gels were characterized by various experimental techniques to investigate their optical, electrical, mechanical, and thermal properties. Further, the PVC gels were examined to construct a compact plano-convex tiny lens structure for varifocal lens application under electrical stimulation. The work revealed that the introduction of a co-plasticizer PC improves the overall dielectric property as well as transparency of the PVC gels. The observed enhancement in dielectric constant of the PC incorporated gels increased up to 6 times of the only DBA plasticized PVC gel (D₉) while the transmittance value is ∼5% higher than that of D₉ gel. Moreover, the optimal ratio of DBA and PC in PVC gel was found to be 8.6:0.4:1 (wt%) and the optimized D_8.6P_0.4 gel induces better actuation properties resulting in improved focal length variation for the developed lens. The proposed adaptive tiny lens could change ist focal length from 3 mm to 20.5 mm with increasing input voltage from 0 V to 1000 V. The developed tiny lens exhibited excellent optical characteristics including fast response speed and good stability. Moreover, this study broadens the scope for property tuning strategies for the electroactive polymer design and application.