TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Components: The flexible material enclosure: is a gel polymer network, a biological membrane, a synthetic membrane, a vesicle, a fluid sack or a droplet; and is permeable to a fluid surrounding the flexible material enclosure. The self-propelled body is a bacterium, an archaea, a protist, a molecular motor, a synthetic colloidal particle, a Janus nanoparticle or a Janus microparticle, where: the bacterium is Escherichia coli; the protist is a self-propelled algae, flagellate or ciliate; and the molecular motor is a cytoskeletal motor, a polymerization motor, a rotary motor, a nucleic acid motor or a synthetic molecular motor. The self-propelled body is a chemotactic, phototactic, gyrotactic, thermotactic, magnetotactic or gravitactic bacterium. The external field is a magnetic field, a gravitational field, an electric field, an optical field, an acoustic field, a light intensity field, a thermal field or a chemical concentration field, where the chemical concentration field is a nutrient field or a toxin field. Preferred Method: In the method (M1), the step of applying a field: is for controlling the size, shape and velocity of the flexible material enclosure; and comprises rendering a translational diffusivity of the self-propelled body anisotropic by applying a force normal to a surface of the flexible material enclosure by the self-propelled body. The step of applying (by the self-propelled body) a force normal to a surface of the flexible material enclosure comprises applying a different force to different surfaces on the flexible material enclosure. The method (M2) further comprises: calculating an estimated speed for the self-propelled bodies, based on a porosity and geometry of the flexible material enclosure, a stoke drag parameter, and a Langevin parameter; rotating the applied field of value (~0c) with a rotation rate of value (~0ext); estimating a shape and size of the flexible material enclosure based upon a diffusivity of the self-propelled bodies; and shrinking, expanding, elongating or translating the flexible material enclosure based on the applying a force (by the self-propelled bodies) normal to a surface of the flexible material enclosure. In the method (M2), the step of rotating the applied field comprises: applying a rotation ratio (~0ext/~0c) of less than 1 to maintain a shape of the flexible material enclosure while gradually changing its translational velocity direction; or applying the rotation ratio of greater than 1 to change a shape of the flexible material enclosure while changing its translational velocity direction stepwise.