Highly stretchable hydrogels for UV curing based high-resolution multimaterial 3D printing

AbstractTraditional 3D printing based on Digital Light Processing Stereolithography (DLP-SL) is unnecessarily limiting as applied to microfluidic device fabrication, especially for high-resolution features. This limitation is due primarily to inherent tradeoffs between layer thickness, exposure time, material strength, and optical penetration that can be impossible to satisfy for microfluidic features. We introduce a generalized 3D printing process that significantly expands the accessible spatially distributed optical dose parameter space to enable the fabrication of much higher resolution 3D components without increasing the resolution of the 3D printer. Here we demonstrate component miniaturization in conjunction with a high degree of integration, including 15 μm × 15 μm valves and a 2.2 mm × 1.1 mm 10-stage 2-fold serial diluter. These results illustrate our approach’s promise to enable highly functional and compact microfluidic devices for a wide variety of biomolecular applications.

Download Full-text

3D Printed Polyurethane Reinforced Graphene Nanoplatelets

Materials Science Forum ◽

10.4028/www.scientific.net/msf.1025.47 ◽

2021 ◽

Vol 1025 ◽

pp. 47-52

Author(s):

Denesh Mohan ◽

Mohd Shaiful Sajab ◽

Saiful Bahari Bakarudin ◽

Rasidi Bin Roslan ◽

Hatika Kaco

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Interfacial Adhesion ◽

Morphological Analysis ◽

Chemical Interaction ◽

Uv Curing ◽

Graphene Nanoplatelets ◽

Digital Light Processing ◽

3D Printed ◽

Strength And Stiffness

3D printing allows industries to scale the development from rapid prototyping to mass production in an easier manner. However, a typical photopolymers resin for stereolithography 3D printing possesses lower mechanical properties which incapable to meet certain industrial requirements for high impact applications. Hence, 0.1 to 2.0 wt.% of graphene nanoplatelets (GnP) were incorporated into photo-curable polyurethane (PU) based resin through digital light processing (DLP) 3D printing to evaluate its reinforcement effect. FTIR spectrum proves that significant characteristics of PU were still dominant upon the addition of GnP, indicating there was no chemical interaction between PU and GnP. The interfacial adhesion and the homogeneity of GnP in PU matrix were investigated through morphological analysis and the strength and stiffness of the 3D-printed composites. Results shows, tensile strength and Young’s Modulus of the PU/1%GnP composite had an increment of 21% and 24%, respectively when compared to neat PU resin. However, further increment of GnP reduced the mechanical properties because of interruption in UV curing during printing, hence leading to interfacial voids and defects on the printed specimens.

Download Full-text

High-resolution 3D printing in seconds

Nature ◽

10.1038/d41586-020-03543-3 ◽

2020 ◽

Vol 588 (7839) ◽

pp. 594-595

Author(s):

Cameron Darkes-Burkey ◽

Robert F. Shepherd

Keyword(s):

High Resolution ◽

3D Printing

Download Full-text

Rapid fabrication of MOF-based mixed matrix membranes through digital light processing

Materials Advances ◽

10.1039/d1ma00023c ◽

2021 ◽

Author(s):

Alexey Pustovarenko ◽

Beatriz Seoane ◽

Edy Abou-Hamad ◽

Helen E King ◽

Bert Weckhuysen ◽

...

Keyword(s):

Additive Manufacturing ◽

3D Printing ◽

Processing Speed ◽

Mixed Matrix Membranes ◽

Scientific Interest ◽

Mixed Matrix ◽

Digital Light Processing ◽

Additive Manufacturing Technology ◽

Rapid Fabrication ◽

Manufacturing Methods

3D printing, also known as additive manufacturing technology, has greatly expanded across multiple sectors of technology replacing classical manufacturing methods by combining processing speed and high precision. The scientific interest...

Download Full-text

Fabrication and Compressive Behavior of a Micro-Lattice Composite by High Resolution DLP Stereolithography

Polymers ◽

10.3390/polym13050785 ◽

2021 ◽

Vol 13 (5) ◽

pp. 785

Author(s):

Chow Shing Shin ◽

Yu Chia Chang

Keyword(s):

High Resolution ◽

Lattice Structure ◽

Low Cost ◽

Hierarchical Structures ◽

Dip Coating ◽

Unit Cell ◽

Digital Light Processing ◽

Unit Cell Size ◽

Wide Range ◽

And Performance

Lattice structures are superior to stochastic foams in mechanical properties and are finding increasing applications. Their properties can be tailored in a wide range through adjusting the design and dimensions of the unit cell, changing the constituent materials as well as forming into hierarchical structures. In order to achieve more levels of hierarchy, the dimensions of the fundamental lattice have to be small enough. Although lattice size of several microns can be fabricated using the two-photon polymerization technique, sophisticated and costly equipment is required. To balance cost and performance, a low-cost high resolution micro-stereolithographic system has been developed in this work based on a commercial digital light processing (DLP) projector. Unit cell lengths as small as 100 μm have been successfully fabricated. Decreasing the unit cell size from 150 to 100 μm increased the compressive stiffness by 26%. Different pretreatments to facilitate the electroless plating of nickel on the lattice structure have been attempted. A pretreatment of dip coating in a graphene suspension is the most successful and increased the strength and stiffness by 5.3 and 3.6 times, respectively. Even a very light and incomplete nickel plating in the interior has increase the structural stiffness and strength by more than twofold.

Download Full-text

Mechanical Properties and Biocompatibility of Urethane Acrylate-Based 3D-Printed Denture Base Resin

Polymers ◽

10.3390/polym13050822 ◽

2021 ◽

Vol 13 (5) ◽

pp. 822

Author(s):

Jy-Jiunn Tzeng ◽

Tzu-Sen Yang ◽

Wei-Fang Lee ◽

Hsuan Chen ◽

Hung-Ming Chang

Keyword(s):

Mechanical Properties ◽

3D Printing ◽

Flexural Modulus ◽

Measurement Data ◽

Uv Exposure ◽

Control Group ◽

Urethane Acrylate ◽

Shore Hardness ◽

Digital Light Processing ◽

Denture Base

In this study, five urethane acrylates (UAs), namely aliphatic urethane hexa-acrylate (87A), aromatic urethane hexa-acrylate (88A), aliphatic UA (588), aliphatic urethane triacrylate diluted in 15% HDD (594), and high-functional aliphatic UA (5812), were selected to formulate five UA-based photopolymer resins for digital light processing (DLP)-based 3D printing. Each UA (40 wt%) was added and blended homogenously with ethoxylated pentaerythritol tetraacrylate (40 wt%), isobornyl acrylate (12 wt%), diphenyl (2,4,6-trimethylbenzoyl) phosphine oxide (3 wt%), and a pink acrylic (5 wt%). Each UA-based resin specimen was designed using CAD software and fabricated using a DLP 3D printer to specific dimensions. Characteristics, mechanical properties, and cytotoxicity levels of these designed UA-based resins were investigated and compared with a commercial 3D printing denture base acrylic resin (BB base) control group at different UV exposure times. Shore hardness-measurement data and MTT assays were analyzed using a one-way analysis of variance with Bonferroni’s post hoc test, whereas viscosity, maximum strength, and modulus were analyzed using the Kruskal–Wallis test (α = 0.05). UA-based photopolymer resins with tunable mechanical properties were successfully prepared by replacing the UA materials and the UV exposure times. After 15 min of UV exposure, the 5812 and 594 groups exhibited higher viscosities, whereas the 88A and 87A groups exhibited lower viscosities compared with the BB base group. Maximum flexural strength, flexural modulus, and Shore hardness values also revealed significant differences among materials (p < 0.001). Based on MTT assay results, the UA-based photopolymer resins were nontoxic. In the present study, mechanical properties of the designed photopolymer resins could be adjusted by changing the UA or UV exposure time, suggesting that aliphatic urethane acrylate has good potential for use in the design of printable resins for DLP-type 3D printing in dental applications.

Download Full-text

Demonstration of a Polymer-Based Single Step Waveguide by 3D Printing Digital Light Processing Technology for Isopropanol Alcohol-Concentration Sensor

Photonic Sensors ◽

10.1007/s13320-021-0626-5 ◽

2021 ◽

Author(s):

Kankan Swargiary ◽

Romuald Jolivot ◽

Waleed Soliman Mohammed

Keyword(s):

Refractive Index ◽

3D Printing ◽

Limit Of Detection ◽

Optical Power ◽

Alcohol Concentration ◽

Single Step ◽

Gap Size ◽

Digital Light Processing ◽

Fused Deposition ◽

The Core

AbstractA polymer based horizontal single step waveguide for the sensing of alcohol is developed and analyzed. The waveguide is fabricated by 3-dimensional (3D) printing digital light processing (DLP) technology using monocure 3D rapid ultraviolet (UV) clear resin with a refractive index of n = 1.50. The fabricated waveguide is a one-piece tower shaped ridge structure. It is designed to achieve the maximum light confinement at the core by reducing the effective refractive index around the cladding region. With the surface roughness generated from the 3D printing DLP technology, various waveguides with different gap sizes are printed. Comparison is done for the different gap waveguides to achieve the minimum feature gap size utilizing the light re-coupling principle and polymer swelling effect. This effect occurs due to the polymer-alcohol interaction that results in the diffusion of alcohol molecules inside the core of the waveguide, thus changing the waveguide from the leaky type (without alcohol) to the guided type (with alcohol). Using this principle, the analysis of alcohol concentration performing as a larger increase in the transmitted light intensity can be measured. In this work, the sensitivity of the system is also compared and analyzed for different waveguide gap sizes with different concentrations of isopropanol alcohol (IPA). A waveguide gap size of 300 µm gives the highest increase in the transmitted optical power of 65% when tested with 10 µL (500 ppm) concentration of IPA. Compared with all other gaps, it also displays faster response time (t = 5 seconds) for the optical power to change right after depositing IPA in the chamber. The measured limit of detection (LOD) achieved for 300 µm is 0.366 µL. In addition, the fabricated waveguide gap of 300 µm successfully demonstrates the sensing limit of IPA concentration below 400 ppm which is considered as an exposure limit by “National Institute for Occupational Safety and Health”. All the mechanical mount and the alignments are done by 3D printing fused deposition method (FDM).

Download Full-text