Measurement of the flexoelectric coefficients e(1) and e(3) in nematic liquid crystals

The flexoelectric coefficients e(1) and e(3) for splay and bend are measured using two experiments. The first experiment measures the sum (e(1)+e(3)) using a pi-cell and applying an ac voltage across the device. The second experiment measures the difference (e(1)-e(3)) using a TN-cell and applying an in-plane quasi-do voltage.