Electrically induced structure and ER effect of DNA particle suspensions

Electrorheological (ER) suspensions were prepared with three types of DNA particles. The DNA particles used were unpurified salmon testes DNA, DNA purified by a standard method, and a DNA/lipid complex. These particles, having the average diameter of 15-20 μm, were respectively dispersed in silicone oil (1000 cSt). It was found from viscosity measurements under a DC electric field ranging between 0 and 2 kV/mm that these suspensions show an ER effect. The increase of viscosity was larger for the suspension of purified DNA particles than those of the unpurified DNA and the DNA/lipid complex suspensions. The ER effect evaluated as relative enhancement of viscosity was large when the particle concentration was 20 wt%. Repeated application of an electric field resulted in stabilized reversible increase of viscosity in response to the field. Although the ER effect of the suspensions prepared with the DNA/lipid complex was not so large, the chemical modification of DNA can be utilized for preparation of various types of DNA-based particles for ER fluids.