Piezoelectricity of a Ferrocene-based Organic Small Molecule

Non-centrosymmetric crystals with piezoelectric properties have emerged as promising materials for smart wearable systems and biomimetic robots. Here we present a novel small ferrocene-based organic molecule crystal (Fc-Cz) possessing high anisotropic-dependent optical and electronic properties, which has been utilized as an ultrasensitive piezoelectric material for the development of a strain sensor. The flexible piezoelectric sensor can distinguish subtle strain or deformations (such as wrist motion) with fast response time (< 40 ms) via detectable piezoelectric signals (I_max = 580 pA). Density functional theory (DFT) indicated that the external pressure can affect the dipole moment by changing the molecular configuration of the asymmetric single crystal Fc-Cz in the crystalline state, leading to a change of polarity, as well as an enhanced dielectric constant. Based on our knowledge, this work is the first example verifying that artificial organic small molecules can serve as simple, stable, high-performance tactile sensors, and this has the potential to open the door to low-cost flexible wearable devices and energy harvesting applications.