The Effect of Printing Parameters and Wood Surface Preparation on the Adhesion of Directly 3D-Printed PLA on Wood

As additive manufacturing technologies advance,new opportunities are opening up for their application in the furniture industry.Wood remains one of the leading raw materials in the furniture industry;therefore,possible options for combining it with 3D printing have been researched.The bonding of 3D-printed polymer parts with wood or 3D printing with wood-plastic composites is already known,but in our research we attempted to directly 3D print polylactic acid(PLA)on wood surfaces.The effect of printing parameters,as well as the surface preparation of wood on the shear strength of the bond between wood and on-printed material was tested.Microscopic images of cross-sections of samples were analyzed.The results show that with a lower initial layer thickness(0.1 mm),a higher printing temperature(220℃),and with the use of polyvinyl acetate(PVAc)primer on the wood surface before 3D printing,a higher bond strength(5.4 MPa)was achieved,but the values for the bond strength remain low compared to the conventional bonding of wood to wood with PVAc adhesive(around 10 MPa).Microscopy studies revealed barely visible penetration of PLA into the lumens of the wood cells.However,the PVAc adhesive used as primer penetrated more into the cell lumens and served as interface layer between deposited melted PLA and the wood,thus creating stronger joints.

Conformal manufacturing of soft deformable sensors on the curved surface

Health monitoring of structures and people requires the integration of sensors and devices on various 3D curvilinear,hierarchically structured,and even dynamically changing surfaces.Therefore,it is highly desirable to explore conformal manufacturing techniques to fabricate and integrate soft deformable devices on complex 3D curvilinear surfaces.Although planar fabrication methods are not directly suitable to manufacture conformal devices on 3D curvilinear surfaces,they can be combined with stretchable structures and the use of transfer printing or assembly methods to enable the device integration on 3D surfaces.Combined with functional nanomaterials,various direct printing and writing methods have also been developed to fabricate conformal electronics on curved surfaces with intimate contact even over a large area.After a brief summary of the recent advancement of the recent conformal manufacturing techniques,we also discuss the challenges and potential opportunities for future development in this burgeoning field of conformal electronics on complex 3D surfaces.

Advances in orthodontic clear aligner materials

Rapid technological improvements in biomaterials,computer-aided design(CAD)and manufacturing(CAM)have endorsed clear aligner therapy(CAT)as a mainstay of orthodontic treatment,and the materials employed for aligner fabrication play an all-important role in determining the clinical performance of clear aligners.This narrative review has attempted to comprehensively encompass the entire gamut of materials currently used for the fabrication of clear aligners and elucidate their characteristics that are crucial in determining their performance in an oral environment.Historical developments and current protocols in aligner fabrication,features of contemporary bioactive materials,and emerging trends related to CAT are discussed.Advances in aligner material chemistry and engineering possess the potential to bring about radical transformations in the therapeutic applications of CAT;in the absence of which,clear aligners would continue to underperform clinically,due to their inherent biomechanical constraints.Finally,while innovations in aligner materials such as shape memory polymers,direct three-dimensional(3D)printed clear aligners and bioactive materials combined with clear aligner materials are essential to further advance the applications of CAT;increased awareness of environmental responsibilities among aligner manufacturers,aligner prescribing clinicians and aligner users is essential for better alignment of our climate change goals towards a sustainable planet.

Kinetically Controlled Supramolecular Block Copolymer Self-Assembly:Multicolor Photonic Crystal Patterns from a Single Formulation

Photonic crystal(PC)patterns with tunable and changeable nonvolatile structural colors printed from a single ink are of great interest for optical products but have rarely been reported because most inks can only output one respective structural color.Herein,we propose a facile yet effective kinetically controlled self-assembly strategy to address this challenge.An ink formulation containing supramolecular block copolymers(SBCPs)is developed.SBCP patterns were printed by direct-ink-writing followed by solvent annealing to generate different structural colors by simply controlling the annealing time.The self-assembly kinetic regime suggests that different colors result from various kinetically trapped metastable states.In turn,the variation in structural color enables“visualization”of the self-assembly dynamics.Furthermore,we demonstrate that these kinetically trapped structures exhibit different responsive color-change behaviors.In addition,this kinetic control strategy can be synergistic with thermodynamic control to extend the color range.This study provides a facile yet effective solution for well-designed PC patterns with tunable,responsive,and unfading colors printed from the simplest single-nozzle printer with a single colorless ink,presenting great potential in broad applications,including information storage,encryption,and anti-fake.

An automatic optimization method for minimizing supporting structures in additive manufacturing

The amount of supporting structure usage has been a major research topic in layer-based additive manufacturing(AM)over the past years as it leads to increased fabrication time and decreased surface quality.Previous studies focused on deformation and topology optimization to eliminate the number of support structures.However,during the actual fabrication process,the properties of shape and topology are essential.Therefore,they should not be modified casually.In this study,we present an optimizer that reduces the number of supporting structures by identifying the prime printing direction.Without rotation,models are projected in each direction in space,and the basis units involved in the generation of support structures are separated.Furthermore,the area of the supporting structures is calculated.Eventually,the prime printing direction with minimal supporting area is obtained through pattern-searching method.The results of the experiment demonstrated that the printing area was reduced by up to 60%for some cases,and the surface quality was also improved correspondingly.Furthermore,both the material consumption and fabrication time were decreased in most cases.In future work,additional factors will be considered,such as the height of the supporting S Xiao-Jun Chen xiaojunchen@sjtu.edu.cn 1 Institute of Biomedical Manufacturing and Life Quality Engineering,State Key Laboratory of Mechanical System and Vibration,School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,P.R.China 2 OMFS-IMPATH Research Group,Department of Imaging and Pathology,Faculty of Medicine,Katholieke Universiteit Leuven,Leuven,Belgium 3 Department of Oral and Maxillofacial Surgery,University Hospitals Leuven,Leuven,Belgium structures and the adhesion locations to improve the efficiency of this optimizer.

Fabrication of perovskite solar cell with high short-circuit current density(Jsc)using moth-eye structure of SiOx

The performance of solar cells is determined by three factors:the open-circuit voltage(Voc),short-circuit current density(Jsc),and fill factor(FF).The Voc and FF are determined by the material bandgap and the series/shunt resistance,respectively.However,Jsc is determined by the amount of incident light in addition to the bandgap of the material.In this study,a moth-eye pattern was formed on a glass surface via direct printing to increase the amount of incident light and thus increase Jsc-The moth-eye pattern is a typical antireflection pattern that reduces the reflection by gradually increasing the refractive index.A flat perovskite solar cell(F-PSC)and a moth-eye patterned perovskite solar cell(M-PSC)had Jsc values of 23.70 and 25.50 mA/cm^2,respectively.The power-conversion efficiencies of the F-PSC and M-PSC were 19.81%and 21.77%,respectively.