Variable stiffness catheter and methods thereof

A variable stiffness catheter comprising:

• an inner layer forming an inner lumen;
• a middle layer forming an annular lumen and surrounding the inner layer,
• the annular lumen of the middle layer being fluidly connected to a vacuum source, the annular lumen comprising a plurality of strings in a single sheet along at least a portion of a length of the inner layer, wherein the plurality of strings are non-crossing;
• and
• an outer layer surrounding the middle layer,
• wherein applying the vacuum and evacuating the annular lumen of the middle layer alters a frictional resistance or adhesion between the inner layer and the outer layer and thereby increases the catheter's flexural rigidity, and wherein releasing the vacuum decreases the catheter's flexural rigidity.