Toward Development of Inflatable Stents with Application in Endovascular Treatments

Abstract

Although design and fabrication of metallic stents are extensively explored and established, the application of inflatable stents in endovascular treatments is relatively new. Inflatable stents introduce several advantages, such as repositionability and conformability to surrounding anatomic structures. These characteristics make the stent suitable for transcatheter treatment of cardiovascular diseases, such as valvular heart disease, and aortic aneurysms. This paper reports on a rapid and cost‐effective fabrication method, based on soft robotic technology, for the development of inflatable stents made of thermoplastic polyurethane. The stent is an inflatable cylinder that contains an array of bonded regions that form a continuous network, resembling a hexagonal lattice pattern. This pattern prevents the stent from buckling into an irregular shape upon inflation. The effect of this pattern on the maximum burst pressure, thickness, and pull‐out force of the stent is characterized. Finally, a trileaflet polyurethane valve is integrated into the inflatable stent frame to demonstrate its application as a transcatheter heart valve. This work serves as a proof of principle that inflatable stents can be useful in cardiovascular applications where conformability to surrounding tissue is advantageous, such as abdominal aortic aneurysm and aortic valve replacement.

Using Soft Robotic Technology to Fabricate a Proof‐of‐Concept Transcatheter Tricuspid Valve Replacement (TTVR) Device

“…The inflatable valve comprises three main parts, the soft inflatable stent with trileaflets that operate as the valve, sealing balloon that prevents paravalvular leakage, and anchoring balloon that enhances anchoring. The soft inflatable stent and trileaflets are fabricated as published recently . Briefly, the inflatable stent is designed based on a hexagonal lattice structure, which has a high filling fraction and its alternating pattern minimizes buckling upon inflation.…”

“…The performance of the valve leaflet function plus its anchoring property can be further studied inside a flow loop. The flow loop is comprises a pump, reservoir, patient‐specific chamber, resistance knob, pressure sensors, regulator, and a compliance chamber . The inflatable valve was deployed inside the patient‐specific test chamber ( Figure a) and infused with 8 mL of water (4 mL inside anchoring balloon and 4 mL inside sealing balloon).…”

“…Once the water‐soluble film is dissolved, a thin (<100 µm) inflatable structure is left that can be interfaced with leaflets to make a functional valve. For an inflatable stent, we discovered that patterning a honeycomb structure into a cylindrical balloon causes it to exerts a uniform radial force, instead of buckling on itself . We have performed preliminary data to show that these inflatable stents can exert significant forces when inflated, despite being comprised of soft materials.…”

“…Therefore, our lab developed a method for fabrication soft actuators from laminated films of polyurethane, that have wall thicknesses down to ≈ 40 µm . We have shown how this new fabrication method can be used to develop inflatable stents for endovascular applications, such as abdominal aortic aneurysm and aortic valve replacement …”

A Catheter‐Deployable Soft Robotic Inflatable Basket for Enhanced Conformability to the Left Atrium of the Heart

“…In conclusion, we designed and fabricated a novel generation of the basket‐catheter for the treatment of AFib and other cardiac arrhythmias. For this purpose, we utilized zero‐thickness soft robotic technology and fabricated six different sizes and geometries of the nonoccluding balloon. These balloons were fabricated by laser cutting thin layers of TPU in specific geometries, and then assembling them into hollow inflatable 3D spherical baskets.…”