Inversely engineered biomimetic flexible network scaffolds for soft tissue regeneration.

Graft-host mechanical mismatch has been a longstanding issue in clinical applications of synthetic scaffolds for soft tissue regeneration. Although numerous efforts have been devoted to resolve this grand challenge, the regenerative performance of existing synthetic scaffolds remains limited by slow tissue growth (comparing to autograft) and mechanical failures. We demonstrate a class of rationally designed flexible network scaffolds that can precisely replicate nonlinear mechanical responses of soft tissues and enhance tissue regeneration via reduced graft-host mechanical mismatch. Such flexible network scaffold includes a tubular network frame containing inversely engineered curved microstructures to produce desired mechanical properties, with an electrospun ultrathin film wrapped around the network to offer a proper microenvironment for cell growth. Using rat models with sciatic nerve defects or Achilles tendon injuries, our network scaffolds show regenerative performances evidently superior to that of clinically approved electrospun conduit scaffolds and achieve similar outcomes to autologous nerve transplantation in prevention of target organ atrophy and recovery of static sciatic index.

Flexible Impact-Resistant Composites with Bioinspired Three-Dimensional Solid-Liquid Lattice Designs.

The ubiquitous solid-liquid systems in nature usually present an interesting mechanical property, the rate-dependent stiffness, which could be exploited for impact protection in flexible systems. Herein, a typical natural system, the durian peel, has been systematically characterized and studied, showing a solid-liquid dual-phase cellular structure. A bioinspired design of flexible impact-resistant composites is then proposed by combining 3D lattices and shear thickening fluids. The resulting dual-phase composites offer, simultaneously, low moduli (e.g., 71.9 kPa, lower than those of many reported soft composites) under quasi-static conditions and excellent energy absorption (e.g., 425.4 kJ/m3, which is close to those of metallic and glass-based lattices) upon dynamic impact. Numerical simulations based on finite element analyses were carried out to understand the enhanced buffering of the developed composites, unveiling a lattice-guided fluid-structure interaction mechanism. Such biomimetic lattice-based flexible impact-resistant composites hold promising potential for the development of next-generation flexible protection systems that can be used in wearable electronics and robotic systems.

Design of a Fuel Explosion-Based Chameleon-Like Soft Robot Aided by the Comprehensive Dynamic Model.

Soft robotics have advantages over the traditional rigid ones to achieve the bending motion but face with challenges to realize the rapid and long-distance linear motion due to the lack of a suitable actuation system. In this paper, a new explosion-based soft robot is proposed to generate the axial fast extension by the explosion pressure. To support and predict the performance of this explosion-based soft robot, a novel dynamic model is developed by considering the change of working fluid (molecular numbers) and some unavoidable and influential factors in the combustion process. Then, based on the physical prototype, a set of experiments is conducted to test the performance of the explosion-based soft robot in performing the axial extensions, as well as to validate the model proposed in this article. It is found that the novel explosion-based soft robot can achieve rapid axial extension by the developed explosion-based actuation system. The explosion-based soft robot can achieve 41-mm displacement at a fuel mass of 180 mg. In addition, the proposed dynamic model can be validated with an average error of 1.5%. The proposed approach in this study provides a promising solution for future high-power density explosion-based soft robots.

Wnt3a-Modified Nanofiber Scaffolds Facilitate Tendon Healing by Driving Macrophage Polarization during Repair.

Inflammation is part of the natural healing response, but persistent inflammatory events tend to contribute to pathology changes of tendon or ligament. Phenotypic switching of macrophages within the inflammatory niche is crucial for tendon healing. One viable strategy to improve the functional and biomechanical properties of ruptured tendons is to modulate the transition from inflammatory to regenerative signals during tendon regeneration at the site of injury. Here, we developed a tendon repair scaffold made of biodegradable polycaprolactone by electrospinning, which was modified to deliver Wnt3a protein and served as an implant to improve tendon healing in a rat model of Achilles tendon defect. During the in vitro study, Wnt3a protein promoted the polarization of M2 macrophages. In the in vivo experiment, Wnt3a scaffold promoted the early recruitment and counting curve of macrophages and increased the proportion of M2 macrophages. Achilles function index and mechanical properties showed that the implantation effect of the Wnt3a group was better than that of the control group. We believe that this type of scaffold can be used to repair tendon defects. This work highlights the beneficial role of local delivery of biological factors in directing inflammatory responses toward regenerative strategies in tendon healing.