Silylated Carbon Nanofiber/Polydimethylsiloxane Based Printable Electrorheological and Sensor Inks for Flexible Electronics.

Electrorheological fluids (ERF) have garnered significant attention for their potential to provide actuation on demand. Similarly, developing stimuli-responsive printable inks for flexible electronics is also gaining antecedence. However, developing a material that demonstrates both functionalities is far and few. Accordingly, a printable ink is made using silylated carbon nanofiber (SiCNF)-polydimethylsiloxane (PDMS). The viscosity of the ink increased by 43%, when subjected to an electric field (E). Robust stability for 20 cycles under E = 300 V mm is noted. The yield stress (τ) value increased by 1600% (E = 600 V mm) compared to zero-field yield stress. Applying temperature with E further increased the τ. In the absence of E, applying temperature not only slowed down the relaxation modulus but also counterintuitively augmented the extent of sluggishness with an increase in temperature. A comprehensive study on the waiting time also indicated a structure build-up within the ink composition happening as the waiting time increases. Accordingly, the time-temperature and time-waiting time superposition principle is applied to predict the long-term behavior of the inks. Further, the printability index of the ink check is studied and used for printing designs using direct ink writing. The printed ink demonstrated pressure sensing capability with a sensitivity of 6.3%/kPa and is stable over 60 cycles.