Mega electrorheological phenomena in graphene nanogels
  Unprecedentedly massive electrorheology has been reported for dilute graphene nanoflakes based ER fluids that have been engineered as novel, readily synthesizable polymeric gels. Polyethylene glycol based graphene gels have been synthesized and very high ER response, 25,000 percent enhancement in viscosity under influence of electric field, has been observed for low concentration systems 2 wt. percent. The gels overcome several drawbacks innate to ER fluids. The gels exhibit long term stability, high graphene packing ratio which ensures very high ER response and the microstructure of the gels ensure that fibrillation of the graphene nanoflakes under field is undisturbed by thermal fluctuations, further leading to mega ER. The gels exhibit large yield stress handling caliber with yield stress observed as high as 13 kPa at 2 wt. perc. graphene. Detailed investigations on the effects of graphene concentration, electric field strength, imposed shear resistance and transients of electric field actuation on the ER response of the gels have been performed. The gels show nearly negligible hysteresis with respect to electro viscous effects which speak of the stability and responsiveness required in transient situations. Indepth analyses with explanations have been provided for the observations and effects, such as sheet over-crowding induced loss of structural integrity at high concentrations and inter flake lubrication or slip induced augmented ER response. The present gels show great promise as potential ER gels for variant smart applications, such as damping and vibration control in active aircraft and vehicle structures, micronanoscale electroactuation, in suspensions or braking clutching in high performance specialized vehicular systems, etc. 
Purbarun Dhar, Ajay Katiyar, Arvind Pattamatta and Sarit K Das
cond-mat.mes-hall cond-mat.soft physics.flu-dyn