Processes for making crush recoverable polymer scaffolds

A method for making balloon-expandable medical device for being implanted in a peripheral vessel of the body, comprising:

• biaxially expanding a polymer precursor to from an expanded tube;
• and
• forming a scaffold from the expanded tube, including forming
• struts joined at crowns to form rings,
• a zero angle radius at the crowns, and
• symmetric closed cells formed by the rings and links connecting the rings;
• wherein the scaffold is capable of regaining more than 90% of its diameter after being crushed to about 50% of its diameter.

A method for crimping a balloon-expandable medical device, comprising:

• forming a pre-crimp scaffold, including the steps of
• biaxially expanding a PLLA precursor to form an expanded tube including the steps of applying a pressure of about 100-120 psi, a heating nozzle rate of about 0.5-0.9 mm/sec and a temperature of about 230-240 Deg Fahrenheit, and
• using a pico-second laser, forming a scaffold from the expanded tube, including forming struts forming ring structures connected by longitudinal links, where there are no more than four links connecting adjacent rings;
• and
• crimping the scaffold to a balloon, including the steps of using a crimping temperature between about 5 to 20 degrees less than the glass transition temperature of PLLA, and maintaining an inflated delivery balloon during crimping to support the scaffold during crimping;
• wherein the scaffold is capable of regaining more than 90% of its diameter after being crushed to about 50% of its diameter.