Co-authors​ :

 Arun ICHANGI (SWITZERLAND), Christina DERICHSWEILER , Sanjay MATHUR , Frank CLEMENS  

The functional properties of one-dimensional (1D) structures, like fibers, have garnered immense interest from the scientific community. The inherent high surface-to-volume ratio, anisotropy, and low defect density of the 1D morphologies have been widely utilized in applications like catalytic, ferroelectric, photovoltaic, etc. Due to its versatility and scalability coupled with the ability to tailor materials morphology and composition for desired applications, electrospinning is an effective technique for preparing 1D fibers. 1D fibers of polymers, ceramics, and composites have been reported for a plethora of applications using the electrospinning technique. In this work, we present the preparation of ferroelectric composites based on electrospun fiber mats of (K,Na)NbO3 (KNN), followed by electrical and functional characterization. Fiber mats of pristine KNN and KNN modified with the inclusion of Li, Ta, and Sb ions in the perovskite lattice were prepared through optimization of sol-gel, electrospinning, and calcination process. Rheological studies on electrospinning solutions show that the prepared solutions exhibit shear-thinning behavior. The influence of binder concentration on the morphology of the calcined material is elucidated through the thermogravimetric analysis. The prepared fiber mats exhibited large signal hysteresis loops with a high leakage current. The observation of switching current behavior in the fiber mats confirms the ferroelectric characteristics, however a saturation of polarization was inhibited by electrical breakdown at high electrical fields. Later, the ferroelectric composites were prepared by embedding 10 wt% of fibers in a PDMS elastomer matrix. The ferroelectric composites were integrated into a tendon-driven soft bending actuator, and the tactile sensing characteristics of the composites were successfully demonstrated through the detection of the touch and release mechanism. This study demonstrates the potential of ferroelectric composites based on 1-D KNN fibers as self-powered, flexible composites for soft-robotic tactile sensors.