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