Steerable probes

1. A steerable probe comprising: a body and a drive mechanism arranged to drive the probe through a sample, wherein the body comprises at least three body sections extending parallel to each other along the probe and each movable relative to the others along the probe, wherein at least two of the body sections are steering sections each of the steering sections being arranged to steer in a respective direction if the steering section is moved forwards of the other body sections, and the drive mechanism is configured to define a desired direction of steering along a curved path through the sample, is configured to move the body sections in a series of step cycles to drive the probe through the sample along the curved path, is configured to move each of the body sections at least one step in each cycle, and is configured to select one of the sections to move first in each cycle, the one of the sections being selected steering the probe in the desired direction along the curved path.

2. The probe according to claim 1 wherein the drive mechanism is arranged to apply a force in a forward direction to one of the body sections, and when applying said force in the forward direction to apply a force in a rearward direction to at least one of the other body sections.

3. The probe according to claim 2 wherein the drive mechanism is arranged to balance said forces so that it applies substantially zero net force to the probe.

4. The probe according to claim 1 wherein the drive mechanism is arranged to act between the body sections so as to apply forces that are internal to the probe.

5. The probe according to claim 1 wherein the steering section comprises a shaped tip.

6. The probe according to claim 1 wherein the steering section comprises resilient biasing means.

7. The probe according to claim 6 wherein the biasing means has a curvature that varies along its length so that, when said at least one body section is longitudinally offset from another of the body sections, it provides a steering curvature that varies with the longitudinal offset.

8. The probe according to claim 1 wherein the steering section comprises an active steering means arranged to provide a steering curvature that varies in response to a control input.

9. The probe according to claim 1 wherein at least one of the body sections is a non-steering section arranged to follow a path defined by the steering section.

10. The probe according to claim 1 wherein each of the body sections has an outer surface which forms part of an outer surface of the probe, the outer surface of the sections having a texture arranged to resist movement through the sample equally in both longitudinal directions of the probe.

11. The probe according to claim 1 wherein the drive mechanism comprises at least one actuator arranged to apply drive forces to the body sections and a controller arranged to control the at least one actuator so as to control movement of the probe.

12. The probe according to claim 11 wherein the at least one actuator is mounted on the probe body and arranged to move with the probe body through the sample.

13. The probe according to claim 1 wherein the distance moved by each of the body sections in each cycle is variable so that a net offset between the body sections can be varied.

14. The probe according to claim 1 wherein the distance moved by each of the body sections in each step is variable so that a net offset between the body sections can be varied.

15. The probe according to claim 1 having a channel extending along it at least one of the body sections.

16. A probe system comprising the probe according to claim 1 and locating means arranged to locate the probe as it moves though the sample, wherein the drive mechanism is arranged to receive location signals from the locating means so as to provide closed loop control of the position of the probe.

17. The probe system according to claim 16 wherein the locating means is arranged to measure the position and orientation of a part of the probe.

18. The probe system according to claim 17 wherein the drive mechanism is arranged to define a desired path of the probe and to determine a positional error and a directional error from the measured position and orientation and the desired path.

19. The probe according to claim 1 further comprising a detection system, wherein the drive mechanism is arranged to determine a desired direction from the detection system and to control the movement of the body sections so as to move the probe towards the desired direction.

20. The probe according to claim 1 wherein three of the sections are steering sections so the probe can be steered in a three dimensional path.