They applied a static electric field. [1] 1. https://patentimages.storage.googleapis.com/d9/34/04/33955717841351/EP0791651A1.pdf https://patentimages.storage.g

They applied a static electric field. [1] 1. https://patentimages.storage.googleapis.com/d9/34/04/33955717841351/EP0791651A1.pdf https://patentimages.storage.googleapis.com/d9/34/04/3395571... 2. https://patentimages.storage.googleapis.com/1c/60/8d/4ddfe080843f65/EP0351357A1.pdf https://patentimages.storage.googleapis.com/1c/60/8d/4ddfe08...