Irregular, angular particles are produced by a manufacturing method that comprises forming a film (10) on a substrate (9) and then stretching the substrate (9) along one or more axes to fracture the film (10) into particle structures. The substrate (9) may be moved continuously along a production line as the film (10) is formed and may be stretched by accelerating that movement. The substrate (9) may comprise a surface with elevated patterns (12) to control the fracturing of the film (10). The particles are particularly suitable for the transdermal delivery of a biologically active substance into the body of a patient.
