Tapered scaffolds
A stent or scaffold has a tapered end or ends. The scaffold is made using an additive manufacturing technique such as stereolithography (SLA). The scaffold may take the shape of a frustum, or a scaffold having one or both of its ends flared. The scaffold has varying mechanical properties over its length, such as a varying ring stiffness, porosity or elasticity modulus. In one embodiment the strut and link widths change linearly from the distal to proximal ends.
1. A medical device, comprising:
a unitary network of rings interconnected by links and forming a scaffold, and the unitary network including a first flared end portion, a second flared end portion and a middle portion located between the flared end portions;
wherein a ring is formed by struts connected at crowns to form a zig-zag or undulating pattern of struts about a bore axis of the scaffold,
wherein a link connects a ring to an adjacent ring at either a Y crown or a W crown, and
wherein
an elasticity modulus for the rings interconnected by links of the flared end portions is constant and has a range of about 0.5 to 1.5 GPa, and the rings interconnected by links of the flared end portions consist of PLLA-co-PCL blended with PEO or PVP, and
an elasticity modulus for the rings interconnected by links of the middle portion has a linearly varying elasticity modulus of 1.0 to 3.5 GPa, and the rings interconnected by links of the middle portion consist of PLLA-co-PCL.
2. The medical device of claim 1 , wherein a width of the struts linearly varies from the first flared end portion to the middle portion, and wherein rings of the middle portion each have about the same diameter.
3. The medical device of claim 1 , wherein a width of the links linearly varies from the first flared end portion to the middle portion.
4. The medical device of claim 1 , wherein a taper at one or both of the first and second flared end portions is linear.
5. The medical device of claim 1 , wherein the scaffold is encased in a sheath.
6. The medical device of claim 5 , wherein the sheath has a higher porosity at a distal and/or proximal end than at a middle portion thereof.
7. The scaffold of claim 1 , wherein an aqueous swellability at the first flared end portion is constant and has a range of 5-20% w/w, an aqueous swellability at the second flared end portion is constant at a range of 5-20% w/w, and an aqueous swellability is constant for the middle portion with a range of 0.05%-2.5%.