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