Thermo-Mechanical Characterization of 4D-Printed Biodegradable Shape-Memory Scaffolds Using Four-Axis 3D-Printing System

Abstract

This study was conducted on different models of biodegradable SMP (shape-memory polymer) scaffolds. A comparison was conducted utilizing a basic FDM (fused deposition modeling)/MEX (material extrusion) printer with a standard printing technique and a novel, modified, four-axis printing method with a PLA (poly lactic acid) polymer as the printing material. This way of making the 4D-printed BVS (biodegradable vascular stent) made it possible to achieve high-quality surfaces due to the difference in printing directions and improved mechanical properties—tensile testing showed a doubling in the elongation at break when using the four-axis-printed specimen compared to the regular printing, of 8.15 mm and 3.92 mm, respectfully. Furthermore, the supports created using this method exhibited a significant level of shape recovery following thermomechanical programming. In order to test the shape-memory effect, after the thermomechanical programming, two approaches were applied: one approach was to heat up the specimen after unloading it inside temperature chamber, and the other was to heat it in a warm bath. Both approaches led to an average recovery of the original height of 99.7%, while the in-chamber recovery time was longer (120 s) than the warm-bath recovery (~3 s) due to the more direct specimen heating in the latter case. This shows that 4D printing using the newly proposed four-axis printing is an effective, promising technique that can be used in the future to make biodegradable structures from SMP.

Advances in Biomimetic Scaffolds for Hard Tissue Surgery

“…This Special Issue presents eleven contributions submitted by scholars with renowned backgrounds in scaffolds design, fabrication, functionalization, or clinical applications [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50]; four of these contributions are valuable review articles, and seven are original new research articles. Thematically, according to the area of application, the contributions can be grouped into articles concerning the following:…”

Thermo-Mechanical Uniaxial Compression of 4D Printed PLA in Wide Range of Strain Rates and Temperatures below Glass Transition Temperature T_g

“…The use of PLA in additive manufacturing enables the production of complex biomedical devices based on computer-aided design and construction (CAD), in particular, with the use of patient-specific anatomical data, the creation of one-of-a-kind implants [36] and prosthesis socket [37]. A new challenge in the field of additive technologies is the application of 3D printing in the production of PLA composites, with or without reinforcement [38], scaffolds [39], biodegradable stents [40] and lately in auxtic energy absorption structures [41][42][43][44][45][46][47]. PLA can also be blended with other materials such as TPU in order to show that by changing the composition and programming temperature, the desired properties for different applications can be achieved so that the highest fixity, recovery, and stress recovery were obtained in hot, cold, and warm-programmed samples by manipulating the input energy and temperature [48].…”

Thermo-Mechanical Behavior and Strain Rate Sensitivity of 3D-Printed Polylactic Acid (PLA) below Glass Transition Temperature (Tg)

“…The use of PLA in additive manufacturing enables the production of complex biomedical devices based on computer-aided design and construction (CAD); in particular, with the use of patient-specific anatomical data, it leads to the creation of one-of-a-kind implants [ 36 ] and prosthesis sockets [ 37 ]. A new challenge in the field of additive technologies is the application of 3D printing in the production of PLA composites, with or without reinforcement [ 38 ], scaffolds [ 39 ], biodegradable stents [ 40 ] and, lately, in auxetic energy absorption structures [ 41 , 42 , 43 , 44 , 45 , 46 , 47 ]. PLA can also be blended with other materials such as TPU in order to show that, by changing the composition and programming temperature, the desired properties for different applications can be achieved so that the highest fixity, recovery, and stress recovery are obtained in hot-, cold-, and warm-programmed samples by manipulating the input energy and temperature [ 48 ].…”