Selective etching of PDMS: Etching technique for application as a positive tone resist

•Etching pure, additive-free and cured PDMS as a positive tone resist is presented.•Selective etching was done by potassium hydroxide and sodium hydroxide.•Etching rate was determined in the function of the irradiation charge density.•Various structures were created with both etchants in 7 μm and 45 μm thick PDMS.