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Abstract: In this paper, the effect of short carbon fiber (SCF), graphite (Gr) and nano-Si3N4 on the friction and wear behavior of polyimide (PI) composites were studied using a block-on-ring arrangement. Experimental results revealed that single incorporation of SCF and Gr can improve the friction-reducing and anti-wear abilities of the PI composites significantly. However, nano-Si3N4 deteriorated the wear resistance of the PI composite drastically as single filler. A synergistic effect was found for the combination of nano-Si3N4 and SCF and Gr, which lead to the best tribological properties. It also can be found that the filled PI composites exhibited better tribological properties under higher PV product (the product of load and sliding speed). Moreover, the filled PI composites showed better tribological properties under oil lubrication and worse tribological properties under water lubrication compared with that under dry sliding condition. [Copyright &y& Elsevier]

[Display omitted] • Biodegradable Filters based on copolymer of Poly(glycerol sebacate) acrylate- co -hydroxyethyl methacrylate were 4D printed. • The filters with suitable transition temperatures and mechanical properties as deployable medical devices. • The copolymer presented excellent cytocompatibility, hemocompatibility and histocompatibility. • The simulated deployment of implants and intercepted of thrombus indicated the clinical feasibility of 4D printing filters. Biodegradable shape memory polymers (SMP) with suitable transition temperatures (T r) and mechanical properties are highly demanded in biomedical field as deployable medical devices. Herein, we report a 4D printing shape memory Inferior Vena Cava Filters (IVCFs), an implantation device, which could prevent the fatal pulmonary embolism, to exemplify the applicability of the biodegradable shape memory polymer in biomedical device field. The IVCF composed of poly(glycerol sebacate) acrylate- co -hydroxyethyl methacrylate (PGSA- co -HEMA) was digital light processing (DLP) 3D printed. The appropriate mechanical property and T r = 37.8 °C, which is close to human body temperature, was tailored by tuning the ratio of the raw material. PGSA-PHEMA presents an excellent cytocompatibility, hemocompatibility and histocompatibility as implants. Besides, in vitro degradation results indicate the biodegradability but withhold the mechanical properties within the service time. Furthermore, the simulated filter deploying and fully emboli interception verifies the successful realization of the concept of rapid, minimally invasive and controllable implantation of the 4D printing of IVCFs through the SMP transformation process, and the feasibility of the filter as well. Therefore, this work provides a new biocompatible SMP and offers a new strategy for developing deployable medical devices. [ABSTRACT FROM AUTHOR]

Thermoset shape memory polyimides (TPIs) are widely used in the fields of high-temperature smart devices. However, the recent molding of polyimides limits most of potentials in the form of two-dimensional film. In this work, we synthesized a novel shape memory polyimide (SMPI) ink that could be used for both Digital Light Process and extrusion molding 3D printing. Through UV-induced free radical polymerization, 3D custom polyimides ink can be cured rapidly. Remarkably, the 3D printed PI exhibits excellent shape memory performance, with R f of 99.8%, R r of 98.3%, therefore the 4D printing PI was successfully prepared. The 3D printed airplane, ultrasonic motor and pagoda can actively recover the film folding, expanding combined compressing, and vertical distorting to their permanent shape, which presents the outstanding 4D printing properties. Moreover, SMPI can be used in extrusion molding to print films, the residual stress induced the self-folding and then a vector model was applied to characterize transformation of extruded plates. In order to develop the application diversity of extruded 4D polyimide, self-folding box and stimuli-response gripper are designed, the gripper is able to pull up steel ball 15 times heavier than itself. Thus, SMPI will be benefit to expand the applied scope of SMPI. Unlabelled Image • A new shape memory polyimide ink for DLP 3D printing and extrusion molding has been developed. • The SMPI have high mechanical strength, excellent shape memory property (R f of 99.8%, R r of 98.3%) and low contraction. • Printed or extruded 4D products can actively recover to their permanent shape in a few minutes. • The SMPI-based self-folding box and stimuli-response gripper have been designed. [ABSTRACT FROM AUTHOR]