Abstract
Liquid crystalline hydrogels are an attractive class of soft materials to direct charge transport, mechanical actuation, and cell migration. When such systems contain supramolecular polymers, it is possible in principle to easily shear align nanoscale structures and create bulk anisotropic properties. However, reproducibly fabricating and patterning aligned supramolecular domains in 3D hydrogels remains a challenge using conventional fabrication techniques. Here, a method is reported for 3D printing of ionically crosslinked liquid crystalline hydrogels from aqueous supramolecular polymer inks. Using a combination of experimental techniques and molecular dynamics simulations, it is found that pH and salt concentration govern intermolecular interactions among the self-assembled structures where lower charge densities on the supramolecular polymers and higher charge screening from the electrolyte result in higher viscosity inks. Enhanced hierarchical interactions among assemblies in high viscosity inks increase the printability and ultimately lead to greater nanoscale alignment in extruded macroscopic filaments when using small nozzle diameters and fast print speeds. The use of this approach is demonstrated to create materials with anisotropic ionic and electronic charge transport as well as scaffolds that trigger the macroscopic alignment of cells due to the synergy of supramolecular self-assembly and additive manufacturing.
| Original language | English (US) |
|---|---|
| Article number | 2005743 |
| Journal | Small |
| Volume | 17 |
| Issue number | 5 |
| DOIs | |
| State | Published - Feb 4 2021 |
Funding
This work was primarily supported by the Air Force Research Laboratory under agreement number FA8650‐15‐2‐5518. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright notation thereon. The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of Air Force Research Laboratory or the U.S. Government. Additional support for the X‐ray studies and molecular dynamics simulations was provided by the Center for Bio‐Inspired Energy Science (CBES), an Energy Frontier Research Center (EFRC) funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award DE‐SC0000989. Additional support for the viscosity analysis was provided by the National Science Foundation (Grant DMR‐1508731). N.A.S. was supported by the Department of Defense (DoD), Air Force Office of Scientific Research, through the National Defense Science and Engineering Graduate (NDSEG) Fellowship, 32 CFR 168a and also acknowledges support from Northwestern University through a Ryan Fellowship. C.V.S. acknowledges funding by the Alexander von Humboldt Foundation through a Feoder Lynen postdoctoral fellowship. X‐ray scattering was performed at the DuPont‐Northwestern‐Dow Collaborative Access Team (DND‐CAT) located at Sector 5 of the Advanced Photon Source (APS). DND‐CAT is supported by Northwestern University, E.I. DuPont de Nemours & Co., and The Dow Chemical Company. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE‐AC02‐06CH11357. This work utilized the following facilities at Northwestern University: the Peptide Synthesis Core Facility and the Analytical BioNanoTechnology Equipment Core facility (ANTEC) of the Simpson Querrey Institute for peptide synthesis and purification, the EPIC facility (TEM and SEM), the MatCI facility (rheology, optical microscopy), the Northwestern University Micro/Nano Fabrication Facility (NUFAB), the Nanomedicine Cleanroom Core Facility of the Simpson Querrey Institute (SQI Cleanroom) and the Center for Advanced Microscopy (CAM) for fluorescence microscopy. ANTEC is supported by the U.S. Army Research Office, the U.S. Army Medical Research and Materiel Command, and Northwestern University provided funding to develop this facility and ongoing support is being received from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF ECCS‐1542205). The EPIC facility of the NUANCE Center has received support from SHyNE; the MRSEC program (NSF DMR‐1121262) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois, through the IIN. The MatCI Facility receives support from the MRSEC Program (NSF DMR‐1720139) of the Materials Research Center at Northwestern University. The SQI Cleanroom is supported by the U.S. Army Research Office, the U.S. Army Medical Research and Materiel Command, the Department of Energy, the Frederick S. Upton Foundation, and Northwestern University, as well as ongoing support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI‐1542205). NUFAB is supported partially by SHyNE, the MRSEC program (NSF DMR‐1121262), the State of Illinois, and Northwestern University. The authors thank Shay Wallace for initial 3D printing set up, Ashwin Narayanan for assistance with pH titrations and illustrations, Qifeng Wang for indentation experiments, Adam Dannenhoffer for providing the CA materials, and Mark Seniw for help with graphics and schemes.
Keywords
- 3D printing
- hierarchical structures
- hydrogels
- liquid crystals
- self-assembly
ASJC Scopus subject areas
- Engineering (miscellaneous)
- General Chemistry
- General Materials Science
- Biotechnology
- Biomaterials