Direct Fused Deposition Modeling 4D Printing and Programming of Thermoresponsive Shape Memory Polymers with Autonomous 2D-to-3D Shape Transformations

Herein, direct 4D printing of thermoresponsive shape memory polymers (SMPs) by the fused deposition modeling (FDM) method that enables programing of 2D objects during printing for autonomous 2D-to-3D shape transformations via simply heating is focused on. The programming process during printing is investigated through designs and experiments. The capability of programming SMPs during printing is illustrated by prestrain and bending capabilities, which are highly related to printing settings, such as nozzle temperature, print speed, layer height, infill patterns, and ratio of active parts in a bilayer structure. A nearly linear relationship for prestrain and bending parameters is experimentally revealed for different printing factors. Quantitative results are presented to be used as a guidance for designing complex 3D structures via 4D printing of 2D structures. Helix structure, twisting structure, DNA-like structures, and functional gripper are designed to demonstrate the potential of direct FDM 4D printing for creating complex 3D structures from simple 2D structures with advantages over traditional manufacturing methods. It is shown that, by removing the need for a layer-by-layer stacking process to achieve a complex 3D shape, FDM can promote sustainability via 4D printing of autonomous 2D-to-3D shape transformer structures with lower materials, time, energy, and longer service life.     

Freestanding 3D Mesostructures,Functional Devices,and Shape‐Programmable Systems Based on Mechanically Induced Assembly with Shape Memory Polymers

Capabilities for controlled formation of sophisticated 3D micro/nanostructures in advanced materials have foundational implications across a broad range of fields. Recently developed methods use stress release in prestrained elastomeric substrates as a driving force for assembling 3D structures and functional microdevices from 2D precursors. A limitation of this approach is that releasing these structures from their substrate returns them to their original 2D layouts due to the elastic recovery of the constituent materials. Here, a concept in which shape memory polymers serve as a means to achieve freestanding 3D architectures from the same basic approach is introduced, with demonstrated ability to realize lateral dimensions, characteristic feature sizes, and thicknesses as small as ≈500, 10, and 5 µm simultaneously, and the potential to scale to much larger or smaller dimensions. Wireless electronic devices illustrate the capacity to integrate other materials and functional components into these 3D frameworks. Quantitative mechanics modeling and experimental measurements illustrate not only shape fixation but also capabilities that allow for structure recovery and shape programmability, as a form of 4D structural control. These ideas provide opportunities in fields ranging from micro‐electromechanical systems and microrobotics, to smart intravascular stents, tissue scaffolds, and many others.     

3D打印形状记忆智能剪纸结构

目的 探究不同切口及不同打印角度形状记忆剪纸结构的拉伸力学性能及形状记忆恢复性能,获得具有较好变形能力和形状记忆恢复能力的智能化剪纸结构。方法 使用FDM打印不同角度的剪纸结构样件,并利用激光切割机获得具有方形切口和圆形切口的样件。对打印角度为0°/90°、±45°的方形切口和圆形切口样件进行常温拉伸实验。为探究温度的影响,进行高温缓慢拉伸实验和高温快速拉伸实验;对比方形切口件和圆形切口件在不同初始应变下的形状记忆恢复能力。结果 在常温下,打印角度为0°/90°的方形切口样件的拉伸距离为1.75 mm,圆形切口样件的拉伸距离为2.50 mm;±45°打印角度的方形切口样件的拉伸距离为3.25 mm,圆形切口样件的拉伸距离为3.00 mm。在高温下,材料进入高弹态,2种切口样件在200%拉伸应变下均未断裂;提高拉伸速率后,方形切口样件的拉伸应变为243.8%,圆形切口样件的拉伸应变为337.5%。结论 将打印角度从0°/90°改为±45°后,方形切口和圆形切口剪纸结构的变形能力均增强。相比于方形切口,圆形切口剪纸结构具有更好的变形能力。高温下剪纸结构的变形能力大大增强;圆形切口剪纸结构样件的形状记忆恢复能力强于方形切口样件的。     

3D Printed Polymer Photodetectors

Extrusion‐based 3D printing, an emerging technology, has been previously used in the comprehensive fabrication of light‐emitting diodes using various functional inks, without cleanrooms or conventional microfabrication techniques. Here, polymer‐based photodetectors exhibiting high performance are fully 3D printed and thoroughly characterized. A semiconducting polymer ink is printed and optimized for the active layer of the photodetector, achieving an external quantum efficiency of 25.3%, which is comparable to that of microfabricated counterparts and yet created solely via a one‐pot custom built 3D‐printing tool housed under ambient conditions. The devices are integrated into image sensing arrays with high sensitivity and wide field of view, by 3D printing interconnected photodetectors directly on flexible substrates and hemispherical surfaces. This approach is further extended to create integrated multifunctional devices consisting of optically coupled photodetectors and light‐emitting diodes, demonstrating for the first time the multifunctional integration of multiple semiconducting device types which are fully 3D printed on a single platform. The 3D‐printed optoelectronic devices are made without conventional microfabrication facilities, allowing for flexibility in the design and manufacturing of next‐generation wearable and 3D‐structured optoelectronics, and validating the potential of 3D printing to achieve high‐performance integrated active electronic materials and devices.     

基于熔融沉积3D打印聚乳酸基复合材料的研究进展

目的 半结晶性聚乳酸(PLA)因透明性好、力学性能优异、能生物降解等优点,在加工领域表现出适用范围广等特性,因此对PLA基复合材料在3D打印技术中的研究应用及最新进展状况进行总结,以期提供借鉴与参考。方法 以熔融沉积成型(FDM)、PLA基体为主线,在查阅近年中外文献基础上,分别从PLA结构性能、3D打印成型工艺、PLA基复合材料改性等方面进行了探讨,着重分析工艺参数的技术优化,以及复合材料的结构改性最新研究进展。结果 FDM制备PLA基复合材料的研究取得了丰硕的成果,在3D打印行业中表现优异,潜力巨大,商品化程度越来越高。结论 低廉、高效、可定制的3D打印受到国内外科研工作者广泛关注与青睐,随着新技术的不断探索和突破,以及纳米材质和新型聚合物材料等新型材质应用,使3D打印在成型加工技术上占据绝对优势。     

Low-Temperature Resistant Stretchable Micro-Supercapacitor Based on 3D Printed Octet-Truss Design

Recently, stretchable micro-supercapacitors (MSCs) that can be easily integrated into electronic devices have attracted research and industrial attentions. In this work, three-dimensional (3D) stretchable MSCs with an octet-truss electrode (OTE) design have been demonstrated by a rapid digital light processing (DLP) process. The 3D-printed electrode structure is beneficial for electrode-electrolyte interface formation and consequently increases the number of ions adsorbed on the electrode surface. The designed MSCs can achieve a high capacitance as ≈74.76 mF cm⁻³ under 1 mA cm⁻³ at room temperature even under a high mechanical deformation, and can achieve 19.53 mF cm⁻³ under 0.1 mA cm⁻³ at a low temperature (−30 °C). Moreover, finite element analysis (FEA) reveals the OTE structure provides 8 times more contact area per unit volume at the electrode-electrolyte interface compared to the traditional interdigital electrode (IDE). This work combines structural design and 3D printing techniques, which provides new insights into highly stretchable MSCs for next-generation electronic devices.     

熔融沉积法3D打印制备氧化锆陶瓷及其力学性能研究

在传统熔融沉积方法的基础上,采用颗粒混合料和螺杆挤出机构3D打印制备了致密和多孔氧化锆陶瓷,系统研究了颗粒原料的打印性能、坯体显微结构特征和陶瓷材料的力学性能。研究结果表明,该方法可以实现倾角达165°和跨度为5.5mm的无支撑结构的打印成型。研究了两种打印路径对致密氧化锆陶瓷抗弯强度及抗弯强度Weibull模数的影响,结果表明与传统单线填充模式相比,"单线+矩形"复合填充模式可以得到更高致密度和更优力学性能的陶瓷(抗弯强度达到637.8 MPa, Weibull模数达到9.10)。研究了不同气孔率多孔氧化锆陶瓷的压缩力学行为,结果表明陶瓷的抗压强度和气孔率之间存在复合指数规律,低气孔率时异面压缩的应力–应变曲线只呈现弹性阶段,高气孔率时出现弹性阶段和坍塌阶段,均未出现密实阶段。     

3D Printable and Reconfigurable Liquid Crystal Elastomers with Light-Induced Shape Memory via Dynamic Bond Exchange

3D printable and reconfigurable liquid crystal elastomers (LCEs) that reversibly shape-morph when cycled above and below their nematic-to-isotropic transition temperature (T_NI) are created, whose actuated shape can be locked-in via high-temperature UV exposure. By synthesizing LCE-based inks with light-triggerable dynamic bonds, printing can be harnessed to locally program their director alignment and UV light can be used to enable controlled network reconfiguration without requiring an imposed mechanical field. Using this integrated approach, 3D LCEs are constructed in both monolithic and heterogenous layouts that exhibit complex shape changes, and whose transformed shapes could be locked-in on demand.     

Hierarchical Atomic Layer Deposited V2O5 on 3D Printed Nanocarbon Electrodes for High-Performance Aqueous Zinc-Ion Batteries

Aqueous rechargeable zinc-ion batteries (ARZIBs) are promising energy storage systems owing to their ecofriendliness, safety, and cost-efficiency. However, the sluggish Zn²⁺ diffusion kinetics originated from its inherent large atomic mass and high polarization remains an ongoing challenge. To this end, electrodes with 3D architectures and high porosity are highly desired. This work reports a rational design and fabrication of hierarchical core–shell structured cathodes (3D@V₂O₅) for ARZIBs by integrating fused deposition modeling (FDM) 3D-printing with atomic layer deposition (ALD). The 3D-printed porous carbon network provides an entangled electron conductive core and interconnected ion diffusion channels, whereas ALD-coated V₂O₅ serves as an active shell without sacrificing the porosity for facilitated Zn²⁺ diffusion. This endows the 3D@V₂O₅ cathode with high specific capacity (425 mAh g^?1 at 0.3 A g^?1), competitive energy and power densities (316 Wh Kg^?1 at 213 W kg^?1 and 163 Wh Kg^?1 at 3400 W kg^?1), and good rate performance (221 mAh g^?1 at 4.8 A g^?1). The developed 3D@V₂O₅ cathode provides a promising model for customized and scalable battery electrode engineering technology. As the ALD-coated layer determines the functional properties, the proposed strategy shows a promising prospect of FDM 3D printing using 1D carbon materials for future energy storage.     

3D Printed Stretchable Tactile Sensors

The development of methods for the 3D printing of multifunctional devices could impact areas ranging from wearable electronics and energy harvesting devices to smart prosthetics and human–machine interfaces. Recently, the development of stretchable electronic devices has accelerated, concomitant with advances in functional materials and fabrication processes. In particular, novel strategies have been developed to enable the intimate biointegration of wearable electronic devices with human skin in ways that bypass the mechanical and thermal restrictions of traditional microfabrication technologies. Here, a multimaterial, multiscale, and multifunctional 3D printing approach is employed to fabricate 3D tactile sensors under ambient conditions conformally onto freeform surfaces. The customized sensor is demonstrated with the capabilities of detecting and differentiating human movements, including pulse monitoring and finger motions. The custom 3D printing of functional materials and devices opens new routes for the biointegration of various sensors in wearable electronics systems, and toward advanced bionic skin applications.     

Remotely Triggered Assembly of 3D Mesostructures Through Shape‐Memory Effects

3D structures that incorporate high‐performance electronic materials and allow for remote, on‐demand 3D shape reconfiguration are of interest for applications that range from ingestible medical devices and microrobotics to tunable optoelectronics. Here, materials and design approaches are introduced for assembly of such systems via controlled mechanical buckling of 2D precursors built on shape‐memory polymer (SMP) substrates. The temporary shape fixing and recovery of SMPs, governed by thermomechanical loading, provide deterministic control over the assembly and reconfiguration processes, including a range of mechanical manipulations facilitated by the elastic and highly stretchable properties of the materials. Experimental demonstrations include 3D mesostructures of various geometries and length scales, as well as 3D aquatic platforms that can change trajectories and release small objects on demand. The results create many opportunities for advanced, programmable 3D microsystem technologies.     

4D Printing-Encapsulated Polycaprolactone–Thermoplastic Polyurethane with High Shape Memory Performances

There are a few shape memory polymers (SMPs) like polylactic acid (PLA) and polyurethane (PU) that are 4D printable, and other SMPs must be synthesized with a complicated chemical lab effort. Herein, considering dual-material extrusion printing and microscopic mechanism behind shape memory effect (SME), bilayer-encapsulated polycaprolactone (PCL)–thermoplastic polyurethane (TPU) shape memory composite structures are 4D printed for the first time. The SME performance is investigated by assessing fixity, shape recovery, stress recovery, and stress relaxation under bending and compression loading modes. PCL, TPU, and melting temperature of PCL play the role of switching phase, net point, and transition temperature, respectively. Due to the destruction and dripping of molten PCL in contact with water, PCL is encapsulated by TPU. Encapsulation successfully solves the challenge of bonding/interface between printed layers, and the results show that the SME performance of the encapsulated structures is higher than bilayer PCL–TPU one's. Experiments reveal that maximum stress recovery in 4D-printed composites remains constant over time. This is a great achievement compared to the previous extrusion-based SMP structures that have great weakness in stress relaxation due to weak and low crystalline fractions and the unraveling of molecular entanglements in semicrystalline and amorphous thermoplastic SMPs, respectively.     

3D Printing technologies for drug delivery: a review

With the FDA approval of the first 3D printed tablet, Spritam®, there is now precedence set for the utilization of 3D printing for the preparation of drug delivery systems. The capabilities for dispensing low volumes with accuracy, precise spatial control and layer-by-layer assembly allow for the preparation of complex compositions and geometries. The high degree of flexibility and control with 3D printing enables the preparation of dosage forms with multiple active pharmaceutical ingredients with complex and tailored release profiles. A unique opportunity for this technology for the preparation of personalized doses to address individual patient needs. This review will highlight the 3D printing technologies being utilized for the fabrication of drug delivery systems, as well as the formulation and processing parameters for consideration. This article will also summarize the range of dosage forms that have been prepared using these technologies, specifically over the last 10 years.     

TiNi基高温形状记忆合金的马氏体相变与形状记忆效应

综述了Ti-Ni基高温形状记忆合金中的马氏体相变和形状记忆效应最近研究进展。Ti-Ni基高温形状记忆合金主要包括用Ti-Ni-Pd,Ti-Ni-Pt,Ti-Ni-Zr和Ti-Ni-Hf等。对Ti-Ni基高温形状记忆合金体材料、薄带和薄膜中的马氏体相变、组织结构、形状记忆效应以及超弹性性能等进行了评述和归纳。值得注意的是,通过适当的时效处理可调节相变温度,显著改善Ti-Ni-Hf高温形状记忆合金的开头记忆效应和超弹性性能,其主要原因在于时效的Ti-Ni-Hf合金中析出纳米级析出相导致基体强度升高。采取适当的制备和加工方法,提高合金的马氏体相变温度,改善合金的开头记忆效应,是当前TiNi基形状记忆合金研究的主要发展趋势。     

Two-Way 4D Printing: A Review on the Reversibility of 3D-Printed Shape Memory Materials

The rapid development of additive manufacturing and advances in shape memory materials have fueled the progress of four-dimensional (4D) printing. With the right external stimulus, the need for human interaction, sensors, and batteries will be eliminated, and by using additive manufacturing, more complex devices and parts can be produced. With the current understanding of shape memory mechanisms and with improved design for additive manufacturing, reversibility in 4D printing has recently been proven to be feasible. Conventional one-way 4D printing requires human interaction in the programming (or shape-setting) phase, but reversible 4D printing, or two-way 4D printing, will fully eliminate the need for human interference, as the programming stage is replaced with another stimulus. This allows reversible 4D printed parts to be fully dependent on external stimuli; parts can also be potentially reused after every recovery, or even used in continuous cycles—an aspect that carries industrial appeal. This paper presents a review on the mechanisms of shape memory materials that have led to 4D printing, current findings regarding 4D printing in alloys and polymers, and their respective limitations. The reversibility of shape memory materials and their feasibility to be fabricated using three-dimensional (3D) printing are summarized and critically analyzed. For reversible 4D printing, the methods of 3D printing, mechanisms used for actuation, and strategies to achieve reversibility are also highlighted. Finally, prospective future research directions in reversible 4D printing are suggested.     

形状记忆基聚合物复合材料的研究进展

形状记忆聚合物是一种新型智能材料,广泛应用于医疗和航天领域。但是传统的形状记忆聚合物由于力学强度低、形变回复力小等缺点使其发展应用受到限制。主要介绍了以各种形状记忆聚合物为基体,添加增强填料来制备形状记忆聚合物复合材料,并且描述了复合材料的形状记忆效应与力学性能和填料的体积分数或质量分数之间的关系,以及形状记忆聚合物复合材料的应用领域与前景。