Direct Fabrication of CsPbxMn1−x(Br,Cl)3 Thin Film by a Facile Solution Spraying Approach

Nowadays, Mn-doping is considered as a promising dissolution for the heavy usage of toxic lead in CsPbX3 perovskite material. Interestingly, Mn-doping also introduces an additional photoluminescence band, which is favorable to enrich the emission gamut of this cesium lead halide. Here, a solution spraying strategy was employed for the direct preparation of CsPbxMn1−x(Br,Cl)3 film through MnCl2 doping in host CsPbBr3 material. The possible fabrication mechanism of the provided approach and the dependences of material properties on Mn-doping were investigated in detail. As the results shown, Pb was partially substituted by Mn as expected. With the ratio of PbBr2:MnCl2 increasing from 3:0 to 1:1, the obtained film separately featured green, cyan, orange-red and pink-red emission, which was caused by the energy transferring process. Moreover, the combining energy of Cs, Pb, and Mn gradually red-shifted resulted from the formation of Cs-Cl, Pb-Cl and Mn-Br coordination bonding as MnCl2 doping increased. In addition, the weight of short decay lifetime of prepared samples increased with the doping rising, which indicated a better exciton emission and less defect-related transition. The aiming of current work is to provide a new possibility for the facile preparation of Mn-doping CsPbX3 film material.

3D printing of metallic micro-gears for micro-fluidic applications

Micro-fluidic devices are essential to handle fluids on the micro-meter scale (micro-scale), making them crucial to biomedical applications, where micro-gear is the key component for active fluid mixing. Rapid and direct fabrication of micro-gears is preferred because they are usually custom-made to specific applications and iterative design is needed. However, conventional manufacturing (CM) techniques for micro-fluidic devices are labor-intensive and time-consuming as multiple steps are required. Three-dimensional (3D) printing, or formally known as additive manufacturing (AM) offers a promising alternative over CM techniques in producing near-net shape complex geometries, given the micro-scale fabrication process. In this work, two types of powder-bed fusion (PBF) AM techniques, namely laser-PBF (L-PBF) and electron beam-PBF (EB-PBF) are used to benchmark 3D-printed micro-gears from stainless steel 316L micro-granular powders. Results showcase the preeminence of L-PBF over EB-PBF in generating distinguishable micro-scale features on gear profiles and superior micro-hardness in mechanical property. Overall, PBF metal AM shows significant promise in advancing the otherwise tedious state of CM for micro-gears.

Direct Fabrication of Micron-Thickness PVA-CNT Patterned Films by Integrating Micro-Pen Writing of PVA Films and Drop-on-Demand Printing of CNT Micropatterns

The direct fabrication of micron-thickness patterned electronics consisting of patterned PVA films and CNT micropatterns still faces considerable challenges. Here, we demonstrated the integrated fabrication of PVA films of micron-thickness and CNT-based patterns by utilising micro-pen writing and drop-on-demand printing in sequence. Patterned PVA films of 1–5 μm in thickness were written first using proper micro-pen writing parameters, including the writing gap, the substrate moving velocity, and the working pressure. Then, CNT droplets were printed on PVA films that were cured at 55–65 °C for 3–15 min, resulting in neat CNT patterns. In addition, an inertia-pseudopartial wetting spreading model was established to release the dynamics of the droplet spreading process over thin viscoelastic films. Uniform and dense CNT lines with a porosity of 2.2% were printed on PVA substrates that were preprocessed at 55 °C for 9 min using a staggered overwriting method with the proper number of layers. Finally, we demonstrated the feasibility of this hybrid printing method by printing a patterned PVA-CNT film and a micro-ribbon. This study provides a valid method for directly fabricating micron-thickness PVA-CNT electronics. The proposed method can also provide guidance on the direct writing of other high-molecular polymer materials and printing inks of other nanosuspensions.

Ferromagnetic soft catheter robots for minimally invasive bioprinting

In vivo bioprinting has recently emerged as a direct fabrication technique to create artificial tissues and medical devices on target sites within the body, enabling advanced clinical strategies. However, existing in vivo bioprinting methods are often limited to applications near the skin or require open surgery for printing on internal organs. Here, we report a ferromagnetic soft catheter robot (FSCR) system capable of in situ computer-controlled bioprinting in a minimally invasive manner based on magnetic actuation. The FSCR is designed by dispersing ferromagnetic particles in a fiber-reinforced polymer matrix. This design results in stable ink extrusion and allows for printing various materials with different rheological properties and functionalities. A superimposed magnetic field drives the FSCR to achieve digitally controlled printing with high accuracy. We demonstrate printing multiple patterns on planar surfaces, and considering the non-planar surface of natural organs, we then develop an in situ printing strategy for curved surfaces and demonstrate minimally invasive in vivo bioprinting of hydrogels in a rat model. Our catheter robot will permit intelligent and minimally invasive bio-fabrication.