skip to main content
US FlagAn official website of the United States government
dot gov icon
Official websites use .gov
A .gov website belongs to an official government organization in the United States.
https lock icon
Secure .gov websites use HTTPS
A lock ( lock ) or https:// means you've safely connected to the .gov website. Share sensitive information only on official, secure websites.

Explore Research Products in the PAR
It may take a few hours for recently added research products to appear in PAR search results.


  • NSF Public Access
  • Search Results
  • Synergistic Effect of Physical and Chemical Cross-Linkers Enhances Shape Fidelity and Mechanical Properties of 3D Printable Low-Modulus Polyesters
Title: Synergistic Effect of Physical and Chemical Cross-Linkers Enhances Shape Fidelity and Mechanical Properties of 3D Printable Low-Modulus Polyesters
Three-dimensional (3D) printing is becoming increasingly prevalent in tissue engineering, driving the demand for low-modulus, high-performance, biodegradable, and biocompatible polymers. Extrusion-based direct-write (EDW) 3D printing enables printing and customization of low-modulus materials, ranging from cell-free printing to cell-laden bioinks that closely resemble natural tissue. While EDW holds promise, the requirement for soft materials with excellent printability and shape fidelity postprinting remains unmet. The development of new synthetic materials for 3D printing applications has been relatively slow, and only a small polymer library is available for tissue engineering applications. Furthermore, most of these polymers require high temperature (FDM) or additives and solvents (DLP/SLA) to enable printability. In this study, we present low-modulus 3D printable polyester inks that enable low-temperature printing without the need for solvents or additives. To maintain shape fidelity, we incorporate physical and chemical cross-linkers. These 3D printable polyester inks contain pendant amide groups as the physical cross-linker and coumarin pendant groups as the photochemical cross-linker. Molecular dynamics simulations further confirm the presence of physical interactions between different pendants, including hydrogen bonding and hydrophobic interactions. The combination of the two types of cross-linkers enhances the zero-shear viscosity and hence provides good printability and shape fidelity.  more » « less
Award ID(s):
2051052 2114640
PAR ID:
10493126
Author(s) / Creator(s):
; ; ; ; ; ;
Publisher / Repository:
JACS
Date Published:
Journal Name:
Biomacromolecules
Volume:
24
Issue:
11
ISSN:
1525-7797
Page Range / eLocation ID:
5091 to 5104
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
More Like this
  1. ; ; ; ; ; ; ; (, Polymer Chemistry)
    null (Ed.)
    Three-dimensional (3D) printing allows for creation of patient-specific implants. However, development of new synthetic materials for 3D printing has been relatively slow with only a few polymers available for tissue engineering applications. Most of these polymers require harsh processing conditions like high temperatures and pressures or are mixed with a combination of leachable additives like plasticizers, initiators, crosslinkers, and solvents to enable 3D printing. Therefore, to propel the development of new polymers for ambient temperature, additive-free 3D printing it is necessary to systematically understand the relationship between the structure of a polymer with its 3D printability. Herein, three homopolyesters were synthesized, each with a common backbone but differing in the length of their saturated, aliphatic pendant chains with 2, 6, or 15 carbons. The physical properties such as the glass transition temperature ( T g ) and the rheological properties like shear thinning, temperature response, and stress relaxation were correlated to the individual polymer's 3D printability. The 3D printability of the polymers was assessed based on four criteria: ability to be extruded as continuous filaments, shape fidelity, the retention of printed shape, and the ability to form free hanging filaments. We observed that the polymers with longer side chains can be extruded at low temperature and pressure because the long side chains act as internal diluents and increase the flowability of the polymer. However, their ability to retain the 3D printed shape is adversely affected by the increase in side chain length, unless the side chains form ordered structures leading to immediate recovery of viscosity. The insight derived from the systematic investigation of the effect of polymer structure on their rheology and 3D printability can be used to rationally design other polymers for extrusion-based direct-write 3D printing. 
    more » « less
  2. ; ; (, Proceedings of the 2021 IISE Annual Virtual Conference)
    The promising success of 3D printing technique with synthetic polymers like nylon, ABS, PLA and epoxy motivates the researchers to put efforts into fabricating constructs with biocompatible natural polymers. The efforts have been broadened into various fields such as bioengineering, manufacturing, and regenerative medicine. Additive biomanufacturing commonly known as 3D bioprinting shows a lot of potential in tissue engineering with those natural polymers. Some challenges such as achieving printability, maintaining geometry in post printing stage, comforting encapsulated cells, and ensuring high proliferation are to be resolved to turn this process into a successful trial. Appropriate design of experiments with a detail rheological investigation can identify useful mechanical properties which is directly related to shape fidelity of 3D bio-printed scaffolds. As candidate natural polymers, Alginate-low viscous Carboxymethyl Cellulose (CMC) was used restricting the solid content 8% (w/v). Various rheological tests, such as the Steady Rate Sweep Test, Thixotropic (3ITT), Amplitude, and Frequency test were performed. The result indicated that rheological properties are CMC dependent. Printability and shape fidelity were analyzed of the filaments and scaffolds fabricated with all the combinations. The rheological results were co-related with the printability and shape fidelity result. 
    more » « less
  3. ; ; (, Biofabrication)
    Abstract Three-dimensional (3D) bioprinting is a promising technique for spatially patterning cells and materials into constructs that mimic native tissues and organs. However, a trade-off exists between printability and biological function, where weak materials are typically more suited for 3D cell culture but exhibit poor shape fidelity when printed in air. Recently, a new class of assistive materials has emerged to overcome this limitation and enable fabrication of more complex, biologically relevant geometries, even when using soft materials as bioinks. These materials include support baths, which bioinks are printed into, and sacrificial inks, which are printed themselves and then later removed. Support baths are commonly yield-stress materials that provide physical confinement during the printing process to improve resolution and shape fidelity. Sacrificial inks have primarily been used to create void spaces and pattern perfusable networks, but they can also be combined directly with the bioink to change its mechanical properties for improved printability or increased porosity. Here, we outline the advantages of using such assistive materials in 3D bioprinting, define their material property requirements, and offer case study examples of how these materials are used in practice. Finally, we discuss the remaining challenges and future opportunities in the development of assistive materials that will propel the bioprinting field forward toward creating full-scale, biomimetic tissues and organs. 
    more » « less
  4. ; ; ; (, International Journal of Molecular Sciences)
    Maintaining shape fidelity of 3D bio-printed scaffolds with soft biomaterials is an ongoing challenge. Here, a rheological investigation focusing on identifying useful physical and mechanical properties directly related to the geometric fidelity of 3D bio-printed scaffolds is presented. To ensure during- and post-printing shape fidelity of the scaffolds, various percentages of Carboxymethyl Cellulose (CMC) (viscosity enhancer) and different calcium salts (CaCl2 and CaSO4, physical cross-linkers) were mixed into alginate before extrusion to realize shape fidelity. The overall solid content of Alginate-Carboxymethyl Cellulose (CMC) was limited to 6%. A set of rheological tests, e.g., flow curves, amplitude tests, and three interval thixotropic tests, were performed to identify and compare the shear-thinning capacity, gelation points, and recovery rate of various compositions. The geometrical fidelity of the fabricated scaffolds was defined by printability and collapse tests. The effect of using multiple cross-linkers simultaneously was assessed. Various large-scale scaffolds were fabricated (up to 5.0 cm) using a pre-crosslinked hybrid. Scaffolds were assessed for the ability to support the growth of Escherichia coli using the Most Probable Number technique to quantify bacteria immediately after inoculation and 24 h later. This pre-crosslinking-based rheological property controlling technique can open a new avenue for 3D bio-fabrication of scaffolds, ensuring proper geometry. 
    more » « less
  5. ; ; ; ; (, Chemical Physics Reviews)
    Embedded ink writing (EIW) and direct ink writing (DIW) constitute the primary strategies for three-dimensional (3D) printing within the realm of material extrusion. These methods enable the rapid fabrication of complex 3D structures, utilizing either yield-stress support baths or self-supporting inks. Both these strategies have been extensively studied across a range of fields, including biomedical, soft robotics, and smart sensors, due to their outstanding print fidelity and compatibility with diverse ink materials. Particle additives capable of forming volume-filling 3D networks are frequently incorporated into polymer solvents. This integration is crucial for engineering the requisite microstructures essential for the formulation of successful support bath and ink materials. The interplay between the particle additives and polymer solvents is critical for achieving rheological tunability in various 3D printing strategies, yet this area has not been systematically reviewed. Therefore, in this critical review, we examined various mechanisms of particle–polymer interactions, the resulting microstructures, and their subsequent impact on mechanical and rheological properties. Overall, this work aims to serve as a foundational guideline for the design of next-generation materials in the field of extrusion additive manufacturing, specifically for EIW and DIW. 
    more » « less
  • Citation Formats
  • MLA
  • APA
  • Chicago
  • BibTeX
  • Save / Share this Record
  • Send to Email