GO-modified flexible polymer nanocomposites fabricated via 3D stereolithography

Graphene oxide (GO) induced enhancement of elastomer properties showed a great deal of potential in recent years, but it is still limited by the barrier of the complicated synthesis processes. Stereolithography (SLA), used in fabrication of thermosets and very recently in “flexible” polymers with elastomeric properties, presents itself as simple and user-friendly method for integration of GO into elastomers. In this work, it was first time demonstrated that GO loadings can be incorporated into commercial flexible photopolymer resins to successfully fabricate GO/elastomer nanocomposites via readily accessible, consumer-oriented SLA printer. The material properties of the resulting polymer was characterized and tested. The mechanical strength, stiffness, and the elongation of the resulting polymer decreased with the addition of GO. The thermal properties were also adversely affected upon the increase in the GO content based on differential scanning calorimetry and thermogravimetric analysis results. It was proposed that the GO agglomerates within the 3D printed composites, can result in significant change in both mechanical and thermal properties of the resulting nanocomposites. This study demonstrated the possibility for the development of the GO/elastomer nanocomposites after the optimization of the GO/“flexible” photoreactive resin formulation for SLA with suitable annealing process of the composite in future

In-situ synchrotron imaging of keyhole mode multi-layer laser powder bed fusion additive manufacturing

The keyhole mode in laser powder bed fusion (LPBF) additive manufacturing can be associated with excessive porosity and spatter, however, the underlying physics in multilayer build conditions remain unclear. Here, we used ultra-fast synchrotron X-ray imaging to reveal this phenomena. We in investigated melt pool dynamics, keyhole porosity and spatter formation mechanisms and their impact in all layers of the build. We observed that the transient melt pool dynamics associated with the keyhole include: (I) keyhole initiation, (II) keyhole development, and (III) melt pool recovery. Porosity and spatter were associated with stages (II) and (III). We also discovered that droplet spatter can form due to the collapse of the keyhole recoil zone, causing molten particle agglomeration and ejection during stage (III). Our results clarify the transient dynamics behind the keyhole mode in a multi-layer LBPF process and can be used to guide the reduction in porosity and spatter in additive manufacturing

Additive manufacturing of energy materials and devices for visible light harvesting

Additive manufacturing of energy materials and devices for visible light harvestin

Upconversion 3D printing via modifaction of a desktop 3D printer

Traditional photopolymer-based 3D printing methods require sequential printing of thin layers, due to short penetration depths of UV or blue light sources used by these techniques. In contrast, our technique circumvents the layer-by-layer limitation by taking advantage of upconversion luminescence processes and the high penetration depths offered by near-infrared (NIR) lasers, allowing for selective crosslinking of voxels at any depth or position within the resin container. The implementation of this technique required a modification of a low-cost FDM printer, by incorporating a 980 nm laser and laser control circuit. The total cost of the parts required for modification was £180. With enhanced penetration depths up to 5.8 cm, the presented technique makes interweaving multicolor, mixed material samples, and metallic plated samples achievable [1], [2]. This method also allows for printing inside or through existing 3D printed parts. This opens doors for restoration of broken items, in situ bioprinting, 3D-circuitry, and notably, 3D printing inside cavities of a different material, illustrating numerous opportunities for practical applications.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Modification of a desktop FFF printer via NIR laser addition for upconversion 3D printing

Traditional photopolymer-based 3D printing methods require sequential printing of thin layers, due to short penetration depths of UV or blue light sources used by these techniques. In contrast, upconversion 3D printing circumvents the layer-by-layer limitation by taking advantage of upconversion luminescence processes and the high penetration depths offered by near-infrared (NIR) lasers, allowing for selective crosslinking of voxels at any depth or position within the resin container. The implementation of this technique required the construction of a 3D printer with the ability of focusing the laser on any point of the space. For this, a low-cost fused filament fabrication (FFF) printer was modified by incorporating a 980 nm laser and laser control circuit. The total cost of the parts required for modification was £180. With enhanced penetration depths up to 5.8 cm, this method also allows for printing inside or through existing 3D printed parts. This opens doors for restoration of broken items, in situ bioprinting, 3D-circuitry, and notably, 3D printing inside cavities of a different material, illustrating numerous opportunities for practical applications

Centimeter-Scale Curing Depths in Laser-Assisted 3D Printing of Photopolymers Enabled by Er³⁺ Upconversion and Green Light-Absorbing Photosensitizer

Photopolymer resins used in stereolithographic 3D printing are limited to penetration depths of less than 1 mm. Our approach explores the use of near-infrared (NIR) to visible upconversion (UC) emissions from lanthanide-based phosphors to initiate photopolymer crosslinking at a much higher depth. This concept relies on the use of invisibility windows and non-linear optical effects to achieve selective crosslinking in photopolymers. SLA resin formulation capable of absorbing light in the visible region (420–550 nm) was developed, in order to take advantage of efficient green-UC of Er3+/Yb3+ doped phosphor. NIR-green light UC shows versatility in enhancing curing depths in laser patterning. For instance, a structure with a curing depth of 11 ± 0.2 mm, cured width of 496 ± 5 µm and aspect ratios of over 22.2:1 in a single pass via NIR-green light UC. The penetration depth of the reported formulation approached 39 mm. Therefore, this technique would allow curing depths of up to 4 cm. Moreover, it was also demonstrated that this technique can initiate cross-linking directly at the focal point. This shows the potential of NIR-assisted UC as a low-cost method for direct laser writing in volume and 3D printing

Routes towards manufacturing biodegradable electronics with polycaprolactone (PCL) via direct light writing and electroless plating

Abstract The electronic industry has room for improvement in adopting cleaner strategies, both in production processes (often energy-intensive and polluting) and in waste management. Many small components like security tags are routinely disposed of via general waste, which could be reduced adopting biodegradable polymers. In this work, a method for selective deposition of metallic micro-tracks on polycaprolactone (PCL) for circuitry integration is presented. The polymer is biodegradable, flexible, suitable for 3D printing, and can be obtained from sustainable sources. Photoreduction of Ag ions was used to generate seeds for subsequent selective electroless copper (Cu) plating in a process that avoids common but undesirable compounds such as cyanides and palladium. Two different photopatterning methods were successfully used to achieve selective Cu plating: flood exposure with a 460 nm light-emitting diode (LED) and direct laser writing (DLW) using a 405 nm laser, achieving 47 ± 11 μm wide tracks. The deposition of uniform Cu layers on PCL substrates is demonstrated, with thicknesses of up to 14 μm and electrical conductivities of up to 2.06 × 107 S m−1, which is near the conductivity of bulk Cu (5.89 × 107 S m−1). Cu-plated interconnects were demonstrated to be fully functional for powering a 5 SMD LEDs circuit. Furthermore, DLW enabled the interconnect manufacturing on an uneven substrate. This method is flexible, selective, low-cost, vacuum-free and of minimized environmental impact, and it provides a new route towards the manufacturing of biodegradable electronics.</jats:p