Due to its inbuilt ability to release biocompatible materials encapsulating living cells in a predefined location, 3D bioprinting is a promising technique for regenerating patient-specific tissues and organs. Among various 3D bioprinting techniques, extrusion-based 3D bio-printing ensures a higher percentage of cell release, ensuring suitable external and internal scaffold architectures. Scaffold architecture is mainly defined by filament geometry and width. A systematic selection of a set of process parameters, such as nozzle diameter, print speed, print distance, extrusion pressure, and material viscosity, can control the filament geometry and width, eventually confirming the user-defined scaffold porosity. For example, carefully selecting two sets of process parameters can result in a similar filament width. However, the lack of availability of sufficient analytical relations between printing process parameters and filament width creates a barrier to achieving defined scaffold architectures with available resources. In this paper, filament width was determined using an image processing technique and an analytical relationship was developed, including various process parameters to maintain defined filament width variation for different hydrogels within an acceptable range to confirm the overall geometric fidelity of the scaffold. Proposed analytical relations can help achieve defined scaffold architectures with available resources.
The ability to manufacture highly intricate designs is one of the key advantages of 3D printing. Achieving high dimensional accuracy requires precise, often time‐consuming calibration of the process parameters. Computerized feedback control systems for 3D printing enable sensing and real‐time adaptation and optimization of these parameters at every stage of the print, but multiple challenges remain with sensor embedment and measurement accuracy. In contrast to these active control approaches, here, the authors harness frontal polymerization (FP) to rapidly cure extruded filament in tandem with the printing process. A temperature gradient present along the filament, which is dependent on the printing parameters, can impose control over this exothermic reaction. Experiments and theory reveal a self‐regulative mechanism between filament temperature and cure kinetics that allows the frontal cure speed to autonomously match the print speed. This self‐regulative printing process rapidly adapts to changes in print speed and environmental conditions to produce complex, high‐fidelity structures and freestanding architectures spanning up to 100 mm, greatly expanding the capabilities of direct ink writing (DIW).
more » « less- Award ID(s):
- 1933932
- NSF-PAR ID:
- 10371241
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 7
- Issue:
- 9
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Abstract -
more » « less
Abstract Advancements in three‐dimensional (3D) printing technology have the potential to transform the manufacture of customized optical elements, which today relies heavily on time‐consuming and costly polishing and grinding processes. However the inherent speed‐accuracy trade‐off seriously constrains the practical applications of 3D‐printing technology in the optical realm. In addressing this issue, here, a new method featuring a significantly faster fabrication speed, at 24.54 mm3h−1, without compromising the fabrication accuracy required to 3D‐print customized optical components is reported. A high‐speed 3D‐printing process with subvoxel‐scale precision (sub 5 µm) and deep subwavelength (sub 7 nm) surface roughness by employing the projection micro‐stereolithography process and the synergistic effects from grayscale photopolymerization and the meniscus equilibrium post‐curing methods is demonstrated. Fabricating a customized aspheric lens 5 mm in height and 3 mm in diameter is accomplished in four hours. The 3D‐printed singlet aspheric lens demonstrates a maximal imaging resolution of 373.2 lp mm−1with low field distortion less than 0.13% across a 2 mm field of view. This lens is attached onto a cell phone camera and the colorful fine details of a sunset moth's wing and the spot on a weevil's elytra are captured. This work demonstrates the potential of this method to rapidly prototype optical components or systems based on 3D printing.
-
Computational Modeling and Experimental Characterization of Extrusion Printing into Suspension Bathsmore » « less
Abstract The extrusion printing of inks into suspension baths is an exciting tool, as it allows the printing of diverse and soft hydrogel inks into 3D space without the need for layer‐by‐layer fabrication. However, this printing process is complex and there have been limited studies to experimentally and computationally characterize the process. In this work, hydrogel inks (i.e., gelatin methacrylamide (GelMA)), suspension baths (i.e., agarose, Carbopol), and the printing process are examined via rheological, computational, and experimental analyses. Rheological data on various hydrogel inks and suspension baths is utilized to develop computational printing simulations based on Carreau constitutive viscosity models of the printing of inks within suspension baths. These results are then compared to experimental outcomes using custom print designs where features such as needle translation speed, defined in this work as print speed, are varied and printed filament resolution is quantified. Results are then used to identify print parameters for the printing of a GelMA ink into a unique guest–host hyaluronic acid suspension bath. This work emphasizes the importance of key rheological properties and print parameters for suspension bath printing and provides a computational model and experimental tools that can be used to inform the selection of print settings.
-
more » « less
Abstract Thermoset elastomers are widely used high‐performance materials due to their thermal stability, chemical resistance, and mechanical properties. However, established casting and molding techniques limit the overall 3D complexity of parts that can be fabricated. Advanced manufacturing methods such as 3D printing have improved design flexibility and reduced development time but have proved challenging using thermally‐cured thermosets due to their viscosity, slow gelation kinetics, and high surface tension. To address this, freeform reversible embedding (FRE) 3D printing extrudes thermosets such as polydimethylsiloxane (PDMS) elastomer within a carbomer support bath, but due to the liquid‐like state of the prepolymer during extrusion has been limited to hollow structures. Here, FRE printing is significantly improved through rheological modification of PDMS with a thixotropic additive (1.0–10.0 wt.%) that imparts a yield stress (30–120 Pa) to help control filament morphology. Further, print process controls consisting of region‐specific slicing, filament retraction, and nonprint travel moves outside of the print to minimize the interaction of the nozzle with previously printed PDMS are implemented. The combined result is the FRE printing of PDMS in complex 3D parts with high fidelity, establishing a 3D printing methodology that can be used broadly with thermally‐cured thermoset elastomers and related polymers.
-
more » « less
Additive manufacturing, commonly known as 3D printing, significantly simplifies the manufacturing process for soft electronics. This work demonstrates the feasibility of a fully 3D‐printed flexible poly(vinylidene fluoride) (PVdF) capacitive temperature sensor. The sensor is constructed using fused deposition modeling (FDM)‐printed PVdF film as the dielectric (thickness ≈180–280 μm) sandwiched between two parallel Direct Ink Writing (DIW) printed silver electrodes (entire device thickness ≈200–380 μm). The motion of the nozzle can facilitate mechanical drawing to the molten PVdF filament, which is a necessary condition to increase the β‐phase content (critical for the sensitivity of the sensor). With optimized printing parameters, the highest β‐phase content (21.30%) is achieved when printing with a nozzle temperature of 200 °C and a print speed of 70 mm s−1. The research demonstrates the application of the device as a temperature sensor by applying heating‐and‐cooling cycles from room temperature (25 °C) up to 140 °C while measuring the capacitance as a function of frequency under different temperatures. The sensor exhibits a stable sensitivity of 3 pF °C−1at 102 Hz and higher frequencies and improved sensitivities at frequencies higher than 102 Hz after dielectric polarization via the corona poling method.
