Characterization of non-spherical polymer particles by combined electrorotation and electroorientation

The electrokinetic properties of non-spherical polymer particles made of SU-8 were characterised by electrorotation (ROT) and electroorientation (EO). Particles with different surface chemistries were analysed. Rod-shaped SU-8 particles were fabricated and chemically modified to produce different surface functionalities. Both ROT and EO spectra were measured for the same particle. The data were analysed to provide values for the surface conductance and permittivity of the particles. For unmodified SU-8 particles the surface conductance was estimated in 0.48 nS, lower than the typical value of 1 nS published for latex spheres. The relative permittivity was estimated as 9.8, suggesting the presence of water in the polymer matrix.