Variable stiffness device, variable stiffness system, endoscope, and stiffness varying method

A variable stiffness device, comprising:

• a first elongated member;
• and
• a second elongated member movable along the first elongated member,
• the first elongated member including:
• a high bending stiffness section including at least one hard member;
• and
• a low bending stiffness section adjacent to the at least one hard member, the low bending stiffness section including a heating member configured to heat the second elongated member,
• the second elongated member including:
• at least one shape-memory unit formed of at least two hollow shape-memory members, each of the shape-memory members being transitionable in phase between a first phase in which the shape-memory member is in a low stiffness state and a second phase in which the shape-memory member is in a high stiffness state on heating by the heating member, the shape-memory member in the high stiffness state having a higher level of stiffness than in the low stiffness state, hollow portions of the shape-memory members being connected together so that the shape-memory unit has a lumen-like inner space configured to allow fluid for cooling the shape-memory members to flow;
• and
• a soft member adjacent to the at least one shape-memory unit, the soft member being softer than the low bending stiffness section and being in a hollow form in which the fluid flows, an inner space of the soft member being connected to the inner space of the shape-memory unit.

A stiffness varying method for a variable stiffness device, the variable stiffness device comprising:

• a shape-memory unit formed of at least two hollow shape-memory members connected together, each of the shape-memory members being transitionable in phase between a first phase in which the shape-memory member is in a low stiffness state and a second phase in which the shape-memory member is in a high stiffness state, the shape-memory member in the high stiffness state having a higher level of stiffness than in the low stiffness state, hollow portions of the shape-memory members being connected together so that the shape-memory unit includes a lumen-like inner space;
• and a heating member,
• the method comprising:
• heating the shape-memory members by the heating member;
• and
• cooling the shape-memory members by causing fluid to flow in the lumen-like inner space.