This means that the nanoparticles replace {TAIL ~ a certain percentage} of the microparticles, which causes a reduction of {HEAD ~ the viscosity}  
This means that the nanoparticles replace { TAIL ~ a certain percentage } of the microparticles , which causes a reduction of { HEAD ~ the viscosity }
OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH