Project description:Recently, soft robots, which are made of soft and light organic materials, have attracted much attention because of improved safety for daily interactions with humans. Mechanically responsive materials that can move macroscopically by external stimuli, such as light and heat, have been studied extensively over the past two decades, and they are expected to be applicable to soft robots. Among them, mechanically responsive crystals are attractive in terms of a larger Young's modulus and faster response speed compared with polymers and gels. However, it is impractical to use one piece of a single crystal as a crystal machine; it is difficult to control the size of crystals and obtain large crystals. Hybridization of crystals with polymers is one way to create actuators with more realistic movements. Herein, we report a hybrid crystal assembly in which plate-like salicylideneaniline crystals are aligned in polymer films by a "rubbing" technique, a new approach which is inexpensive, easy, and applicable to a wide range of crystals and polymers. The hybrid films bent reversibly upon alternate irradiation with ultraviolet and visible light. The hybrid films bent as fast as single crystals, even when larger than single-crystal size, showing great mechanical performance originating from the advantages of both molecular crystals (fast response time) and polymers (large size). This work enriches the development of light-driven hybrid actuators composed of molecular crystals and polymers.
Project description:Stem cells are capable of sensing and processing environmental inputs, converting this information to output a specific cell lineage through signaling cascades. Despite the combinatorial nature of mechanical, thermal, and biochemical signals, these stimuli have typically been decoupled and applied independently, requiring continuous regulation by controlling units. We employ a programmable polymer actuator sheet to autonomously synchronize thermal and mechanical signals applied to mesenchymal stem cells (MSCs). Using a grid on its underside, the shape change of polymer sheet, as well as cell morphology, calcium (Ca2+) influx, and focal adhesion assembly, could be visualized and quantified. This paper gives compelling evidence that the temperature sensing and mechanosensing of MSCs are interconnected via intracellular Ca2+ Up-regulated Ca2+ levels lead to a remarkable alteration of histone H3K9 acetylation and activation of osteogenic related genes. The interplay of physical, thermal, and biochemical signaling was utilized to accelerate the cell differentiation toward osteogenic lineage. The approach of programmable bioinstructivity provides a fundamental principle for functional biomaterials exhibiting multifaceted stimuli on differentiation programs. Technological impact is expected in the tissue engineering of periosteum for treating bone defects.
Project description:Soft robotics may enable many new technologies in which humans and robots physically interact, yet the necessary high-performance soft actuators still do not exist. The optimal soft actuators need to be fast and forceful and have programmable shape changes. Furthermore, they should be energy efficient for untethered applications and easy to fabricate. Here, we combine desirable characteristics from two distinct active material systems: fast and highly efficient actuation from dielectric elastomers and directed shape programmability from liquid crystal elastomers. Via a top-down photoalignment method, we program molecular alignment and localized giant elastic anisotropy into the liquid crystal elastomers. The linearly actuated liquid crystal elastomer monoliths achieve strain rates over 120% per second with an energy conversion efficiency of 20% while moving loads over 700 times the elastomer weight. The electric actuation mechanism offers unprecedented opportunities toward miniaturization with shape programmability, efficiency, and more degrees of freedom for applications in soft robotics and beyond.
Project description:In recent years, light-guided robotic soft actuators have attracted intense scientific attention and rapidly developed, although it still remains challenging to precisely and reversibly modulate the moving directions and shape morphing modes of soft actuators with ease of stimulating operation. Here we report a strategy of building a multi-stimuli-responsive liquid crystal elastomer soft actuator system capable of performing not only multi-directional movement, but also different shape morphing modes. This strategy is based on the selective stimulation of specific domains of the hierarchical structured actuator through the modulation of three wavelength bands (520, 808, 980?nm) of light stimulus, which release the actuation system from light scanning position/direction restriction. Three near-infrared dual-wavelength modulated actuators and one visible/infrared tri-wavelength modulated multi-directional walker robot are demonstrated in this work. These devices have broad application prospects in robotic and biomimetic technology.
Project description:A hydrogel exhibits a real-time depth-controllable swimming motion via light-mediated modulation of local density to mimic the volume changes found in the bladders of fish. Moreover, other motions, e.g., rolling, somersaulting, and bipedal-like walking, can also be realized by designing or combining gel shapes, and the location of light.
Project description:Transient delivery of gene circuits is required in many potential applications of synthetic biology, yet the pre-steady-state processes that dominate this delivery route pose major challenges for robust circuit deployment. Here we show that site-specific recombinases can rectify undesired effects by programmable timing of gene availability in multigene circuits. We exemplify the concept with a proportional sensor for endogenous microRNA (miRNA) and show a marked reduction in its ground state leakage due to desynchronization of the circuit's repressor components and their repression target. The new sensors display a dynamic range of up to 1,000-fold compared to 20-fold in the standard configuration. We applied the approach to classify cell types on the basis of miRNA expression profile and measured >200-fold output differential between positively and negatively identified cells. We also showed major improvements in specificity with cytotoxic output. Our study opens new venues in gene circuit design via judicious temporal control of circuits' genetic makeup.
Project description:We propose a novel filter circuit that incorporates a double ring resonator with a balanced Mach-Zehnder interferometer (MZI). The circuit has a response equivalent to a conventional ring loaded MZI filter, but with added flexibility in terms of configurability. The second-order filter can also be cascaded to realize higher-order filters. The circuit incorporates a two-stage input and output coupler to further reduce the effect of dispersion. A combination of local and global optimization strategies to program the filter, using tailored objective functions, have been tested in simulation and experiments. To our best knowledge, this is the first time a global optimization strategy is directly used in ARMA filter synthesis and simulation without any additional requirement. We further extend the optimization strategy into experiments and demonstrated its use in practical case for programmable filter circuits.
Project description:Soft actuation allows robots to interact safely with humans, other machines, and their surroundings. Full exploitation of the potential of soft actuators has, however, been hindered by the lack of simple manufacturing routes to generate multimaterial parts with intricate shapes and architectures. Here, we report a 3D printing platform for the seamless digital fabrication of pneumatic silicone actuators exhibiting programmable bioinspired architectures and motions. The actuators comprise an elastomeric body whose surface is decorated with reinforcing stripes at a well-defined lead angle. Similar to the fibrous architectures found in muscular hydrostats, the lead angle can be altered to achieve elongation, contraction, or twisting motions. Using a quantitative model based on lamination theory, we establish design principles for the digital fabrication of silicone-based soft actuators whose functional response is programmed within the material's properties and architecture. Exploring such programmability enables 3D printing of a broad range of soft morphing structures.
Project description:Polymeric shape-memory elastomers can recover to a permeant shape from any programmed deformation under external stimuli. They are mostly cross-linked polymeric materials and can be shaped by three-dimensional (3D) printing. However, 3D printed shape-memory polymers so far only exhibit elasticity above their transition temperature, which results in their programmed shape being inelastic or brittle at lower temperatures. To date, 3D printed shape-memory elastomers with elasticity both below and above their transition temperature remain an elusive goal, which limits the application of shape-memory materials as elastic materials at low temperatures. In this paper, we printed, for the first time, a custom-developed shape-memory elastomer based on polyethylene glycol using digital light processing, which possesses elasticity and stretchability in a wide temperature range, below and above the transition temperature. Young's modulus in these two states can vary significantly, with a difference of up to 2 orders of magnitude. This marked difference in Young's modulus imparts excellent shape-memory properties to the material. The difference in Young's modulus at different temperatures allows for the programming of the pneumatic actuators by heating and softening specific areas. Consequently, a single actuator can exhibit distinct movement modes based on the programming process it undergoes.
Project description:Soft robotic systems are increasingly emerging as robust alternatives to conventional robotics. Here, we demonstrate the development of programmable soft actuators based on volume expansion/retraction accompanying liquid-vapor phase transition of a phase-change material confined within an elastomer matrix. The combination of a soft matrix (a silicone-based elastomer) and an embedded ethanol-impregnated polyacrylonitrile nanofiber (PAN NF) mat makes it possible to form a sealed compound device that can be operated by changing the actuator temperature above/below the boiling point of ethanol. The thermo-responsive actuators based on this principle demonstrate excellent bending ability at a sufficiently high temperature (>90 °C) - comparable with compressed air-based soft actuators. The actuator using the mechanism presented here is easy to manufacture and automate and is recyclable. Finally, the actuation mechanism can be incorporated into a wide variety of shapes and configurations, making it possible to obtain tunable and programmable soft robots that could have a wide variety of industrial applications.