Medical devices such as catheters can include structure or provision that permit a physician or other health care professional to adjust the stiffness of at least a portion of the medical device. In some instances, the medical device may be adjusted prior to inserting the medical device into a patient. In some cases, the medical device may be adjusted while in use within the patient.

Medical devices such as catheters can include structure or provision that permit a physician or other health care professional to adjust the stiffness of at least a portion of the medical device. In some instances, the medical device may be adjusted prior to inserting the medical device into a patient. In some cases, the medical device may be adjusted while in use within the patient.

Insertion tool for inserting at least a part of a medical device into a subject, insertion device comprising the insertion tool and an insertion mechanism, and method for manufacturing the insertion tool, wherein the insertion tool comprises a penetrating portion that comprises a composite material comprising at least one first material and at least one second material. Wherein the first material is an amorphous material or amorphous composite and the second material is a fibrillary material or fibrillary composite or a crystalline material or crystalline composite. A fluid absorption of the first material of the composite material is higher than a fluid absorption of the second material of the composite material, and the insertion device is adapted to soften when in contact with a body fluid at least due to the fluid absorption of the amorphous material or amorphous composite.