4D Printing of High-Performance Thermal-Responsive Liquid Metal Elastomers Driven by Embedded Microliquid Chambers.

Four-dimensional (4D) printing of swellable materials have been viewed as an ideal approach to build shape morphing architectures. However, there is less variety in high-performance swellable materials, limiting its development. To address this challenge, we proposed a new strategy for designing high-performance thermal-responsive swellable materials. The reversible liquid-vapor phase change of embedded low boiling point liquid chambers and functional liquid metal fillers endows the designed elastomer with the reversible thermal-responsive swellable property with high stability, fast response speed, and large equilibrium deformation. Notably, liquid metal fillers play a crucial role in improving the thermal-responsive property via improving the thermal conductivity and fracture toughness and decreasing the stiffness. To demonstrate the feasibility of constructing shape morphing architectures with proposed thermal-responsive liquid metal elastomers, typical bilayer structures were printed and investigated. By altering the key design parameters, the response speed and equilibrium deformation can be adjusted as needed. Therefore, complex shape morphing architectures can be printed. This study could provide a new avenue to design swellable material systems for 4D printing of shape morphing architectures.

Multimaterial 3D Printing of Highly Stretchable Silicone Elastomers.

3D printing of silicone elastomers with the direct ink writing (DIW) process has demonstrated great potential in areas as diverse as flexible electronics, medical devices, and soft robotics. However, most of current silicones are not printable because of their low viscosity and long curing time. The lack of systematic research on materials, devices, and processes during printing makes it a huge challenge to apply the DIW process more deeply and widely. In this report, aiming at the dilemmas in materials, devices, and processes, we proposed a comprehensive guide for printing highly stretchable silicone. Specifically, to improve the printability of silicone elastomers, nanosilica was added as a rheology modifier without sacrificing any stretching ability. To effectively control print speed and accuracy, a theoretical model was built and verified. With this strategy, silicone elastomers with different mechanical properties can all be printed and can realize infinite time and high speed printing (>25 mm/s) while maintaining accuracy. Here, super-stretchable silicone that can be stretched to 2000% was printed for the first time, and complex structures can be printed with high quality. For further demonstration, prosthetic nose, data glove capable of detecting fingers' movement, and artificial muscle that can lift objects were printed directly. We believe that this work could provide a guide for further work using the DIW process to print soft matters in a wide range of application scenarios.

Patient-specific three-dimensional printed heart models benefit preoperative planning for complex congenital heart disease.

BACKGROUND: Preoperative planning for children with congenital heart diseases remains crucial and challenging. This study aimed to investigate the roles of three-dimensional printed patient-specific heart models in the presurgical planning for complex congenital heart disease. METHODS: From May 2017 to January 2018, 15 children diagnosed with complex congenital heart disease were included in this study. Heart models were printed based on computed tomography (CT) imaging reconstruction by a 3D printer with photosensitive resin using the stereolithography apparatus technology. Surgery options were first evaluated by a sophisticated cardiac surgery group using CT images only, and then surgical plans were also set up based on heart models. RESULTS: Fifteen 3D printed heart models were successfully generated. According to the decisions based on CT, 13 cases were consistent with real options, while the other 2 were not. According to 3D printed heart models, all the 15 cases were consistent with real options. Unfortunately, one child diagnosed with complete transposition of great arteries combined with interruption of aortic arch (type A) died 5 days after operation due to postoperative low cardiac output syndrome. The cardiologists, especially the younger ones, considered that these 3D printed heart models with tangible, physical and comprehensive illustrations were beneficial for preoperative planning of complex congenital heart diseases. CONCLUSION: 3D printed heart models are beneficial and promising in preoperative planning for complex congenital heart diseases, and are able to help conform or even improve the surgery options.

Three-Dimensional Printed Wearable Sensors with Liquid Metals for Detecting the Pose of Snakelike Soft Robots.

Liquid metal (LM)-based flexible sensors, which utilize advanced liquid conductive materials to serve as sensitive elements, are emerging as a promising solution to measure large deformations. Nowadays, one of the biggest challenges for precise control of soft robots is the detection of their real-time positions. Existing fabrication methods are unable to fabricate flexible sensors that match the shape of soft robots. In this report, we first described a novel 3D printed multifunction inductance flexible and stretchable sensor with LMs, which is capable of measuring both axial tension and curvature. This sensor is fabricated with a developed coaxial LM 3D printer by coprinting of silicone rubber and LMs. Because of the solenoid shape, this sensor can be easily installed on snakelike soft robots and can accurately distinguish different degrees of tensile and bending deformations. We determined the structural parameters of the sensor and proved its excellent stability and reliability. As a demonstration, we used this sensor to measure the curvature of a finger and feedback the position of an endoscope, a typical snakelike structure. Because of its bending deformation form consistent with the actual working status of the soft robot and unique shape, this sensor has better practical application prospects in the pose detection.

3D printed Lego®-like modular microfluidic devices based on capillary driving.

The field of how to rapidly assemble microfluidics with modular components continuously attracts researchers' attention, however, extra efforts must be devoted to solving the problems of leaking and aligning between individual modules. This paper presents a novel type of modular microfluidic device, driven by capillary force. There is no necessity for a strict seal or special alignment, and its open structures make it easy to integrate various stents and reactants. The key rationale for this method is to print different functional modules with a low-cost three-dimensional (3D) printer, then fill the channels with capillary materials and assemble them with plugs like Lego® bricks. This rapidly reconstructed modular microfluidic device consists of a variety of common functional modules and other personalized modules, each module having a unified standard interface for easy assembly. As it can be printed by a desktop 3D printer, the manufacturing process is simple and efficient, with controllable regulation of the flow channel scale. Through diverse combinations of different modules, a variety of different functions can be achieved, without duplicating the manufacturing process. A single module can also be taken out for testing and analysis. What's more, combined with basic circuit components, it can serve as a low-cost Lego®-like modular microfluidic circuits. As a proof of concept, the modular microfluidic device has been successfully demonstrated and used for stent degradation and cell cultures, revealing the potential use of this method in both chemical and biological research.

From Microfluidic Paper-Based Analytical Devices to Paper-Based Biofluidics with Integrated Continuous Perfusion.

As a kind of facile tool, microfluidic paper-based analytical devices (µPADs) have been widely used in analytical and biomedical fields. However, because we lack the ability to control the continuous perfusion of these devices, they are not generally used in fields that require continuous flow, especially biofluidics fields such as cell culturing, drug screening, and organs on chips. In this study, we designed a novel, low-cost, and compact platform that can be used to control the continuous perfusion of µPADs. As most of the parts of this platform can be created using a three-dimensional (3D) desktop printer, our platform can be easily duplicated by other researchers. We demonstrate that with our system, µPADs can be promising paper-based biofluidic platforms for cell culturing and drug screening.

3D Printed Paper-Based Microfluidic Analytical Devices.

As a pump-free and lightweight analytical tool, paper-based microfluidic analytical devices (µPADs) attract more and more interest. If the flow speed of µPAD can be programmed, the analytical sequences could be designed and they will be more popular. This reports presents a novel µPAD, driven by the capillary force of cellulose powder, printed by a desktop three-dimensional (3D) printer, which has some promising features, such as easy fabrication and programmable flow speed. First, a suitable size-scale substrate with open microchannels on its surface is printed. Next, the surface of the substrate is covered with a thin layer of polydimethylsiloxane (PDMS) to seal the micro gap caused by 3D printing. Then, the microchannels are filled with a mixture of cellulose powder and deionized water in an appropriate proportion. After drying in an oven at 60 °C for 30 min, it is ready for use. As the different channel depths can be easily printed, which can be used to achieve the programmable capillary flow speed of cellulose powder in the microchannels. A series of microfluidic analytical experiments, including quantitative analysis of nitrite ion and fabrication of T-sensor were used to demonstrate its capability. As the desktop 3D printer (D3DP) is very cheap and accessible, this device can be rapidly printed at the test field with a low cost and has a promising potential in the point-of-care (POC) system or as a lightweight platform for analytical chemistry.

A facile and low-cost micro fabrication material: flash foam.

Although many microfabrication methods have been reported, the preliminary replication templates used in most microfabrication still depend on the expensive and long-period photolithography. This paper explores an alternative replication templates based on a daily used material, flash foam (FF), and proposes a facile microfabrication method, flash foam stamp lithography (FFSL). When FF is exposed with a desired pattern mask, the negative of the pattern is transferred to its surface and micro structures are formed due to the shrinkage of the exposed area. As FF is commonly used in personal stamps, FFSL is very simple and cost-effective. In this paper, we demonstrated that FF is a good and low-cost template for many micro fabrication methods, such as micro casting and soft lithography. Thus, designing and fabricating micro structures at personal office immediately become possible with FFSL. Furthermore, we demonstrated that multi-scale micro structures can be easily fabricated by double exposure with FFSL. Skin textures is used as another case to demonstrate that FFSL can fabricate structures with different depth in a single exposure. As a result, FF shows a promising future in biology, and analytical chemistry, such as rapid fabrication of point of care diagnostics and microfluidic analytical devices with low cost.

Coaxial nozzle-assisted 3D bioprinting with built-in microchannels for nutrients delivery.

This study offers a novel 3D bioprinting method based on hollow calcium alginate filaments by using a coaxial nozzle, in which high strength cell-laden hydrogel 3D structures with built-in microchannels can be fabricated by controlling the crosslinking time to realize fusion of adjacent hollow filaments. A 3D bioprinting system with a Z-shape platform was used to realize layer-by-layer fabrication of cell-laden hydrogel structures. Curving, straight, stretched or fractured filaments can be formed by changes to the filament extrusion speed or the platform movement speed. To print a 3D structure, we first adjusted the concentration and flow rate of the sodium alginate and calcium chloride solution in the crosslinking process to get partially crosslinked filaments. Next, a motorized XY stages with the coaxial nozzle attached was used to control adjacent hollow filament deposition in the precise location for fusion. Then the Z stage attached with a Z-shape platform moved down sequentially to print layers of structure. And the printing process always kept the top two layers fusing and the below layers solidifying. Finally, the Z stage moved down to keep the printed structure immersed in the CaCl2 solution for complete crosslinking. The mechanical properties of the resulting fused structures were investigated. High-strength structures can be formed using higher concentrations of sodium alginate solution with smaller distance between adjacent hollow filaments. In addition, cell viability of this method was investigated, and the findings show that the viability of L929 mouse fibroblasts in the hollow constructs was higher than that in alginate structures without built-in microchannels. Compared with other bioprinting methods, this study is an important technique to allow easy fabrication of lager-scale organs with built-in microchannels.

Fabrication of low cost soft tissue prostheses with the desktop 3D printer.

Soft tissue prostheses such as artificial ear, eye and nose are widely used in the maxillofacial rehabilitation. In this report we demonstrate how to fabricate soft prostheses mold with a low cost desktop 3D printer. The fabrication method used is referred to as Scanning Printing Polishing Casting (SPPC). Firstly the anatomy is scanned with a 3D scanner, then a tissue casting mold is designed on computer and printed with a desktop 3D printer. Subsequently, a chemical polishing method is used to polish the casting mold by removing the staircase effect and acquiring a smooth surface. Finally, the last step is to cast medical grade silicone into the mold. After the silicone is cured, the fine soft prostheses can be removed from the mold. Utilizing the SPPC method, soft prostheses with smooth surface and complicated structure can be fabricated at a low cost. Accordingly, the total cost of fabricating ear prosthesis is about $30, which is much lower than the current soft prostheses fabrication methods.

[The textual research on FANG Dao's life and Fangshijiacangjiyaofang (Collected prescription of Fang family's).].

Fangshijiacangjiyaofang (Collected prescription of Fang family's) is a prescription book compiled by Fang Dao in Southern Song Dynasty, and most of these prescriptions from experience have important clinical guiding values. However, few recorders about the book and its compiler could be found in relevant literature, it is necessary for them to be further verified.