Polymer composites that exhibit piezoresistive behavior have been actively sought in the emerging field of flexible electronics as a replacement for traditional metallic or semiconductor-based devices. A particularly attractive area of application for these flexible piezoresistors is their use as pressure sensors due to their ability to endure large mechanical strains (stretchability) while retaining their electrical conductivity. Magnetic field manipulation of metallic particles with high magnetic susceptibilities (Fe, Co, Ni) is an effective technique to fabricate anisotropic composites by forming pearl-chain columns that drastically reduce the concentration of fillers required to produce enhanced piezoresistive performance. The alignment of particles in the through-thickness direction creates induced percolation thereby resulting in a lightweight, optically transparent, and conformable composite. 

This review aims to provide an insight into the research advances in the development of flexible piezoresistive composites via a mechanistic understanding of the structural evolution of column structures during the alignment process. Various strategies employed to improve column morphology by tuning processing conditions are explored with the foresight of implementing it on roll-to-roll manufacturing technology. Finally, the influence of the mechanical modulus of the viscoelastic polymer matrix on the final composite property is also addressed to highlight the importance of careful design procedures that need to be adopted to maximize the sensitivity and stability of these pressure sensing elements.