Smart material

About: Smart material is a research topic. Over the lifetime, 3704 publications have been published within this topic receiving 74280 citations. The topic is also known as: intelligent material & responsive material.

Pneumatic smart surfaces with rapidly switchable dominant and latent superhydrophobicity

Abstract: Smart surfaces that possess switchable wettability are highly desired for a broad range of applications. However, the realization of novel approaches enabling complete alteration of surface properties independent of chemical environment and special materials is still challenging. Herein, inspired by the air sacs of insects, we fabricate a pneumatic smart surface that possesses dual-property wetting behavior and permits fast switching between states. The pneumatic surface is based on an embedded micro-air-sac network composed of an elastomer that was fabricated via a stretching-assisted mismatch-bonding process. By simply pumping the air sacs, the surface could undergo rapid and large-amplitude topography deformation, thereby exposing one surface and hiding the other, and the dominant surface and the latent surface could be switched reversibly. As a typical example, we demonstrate a smart surface with contrasting ‘petal’ and ‘lotus’ effects that enables the on-demand capture and release of water droplets. Our pneumatic strategy demonstrates a currently underexploited platform for the development of switchable smart surfaces. Inspired by the air sacs of insects, a team in China has developed a smart surface that can deliver liquid droplets to a desired location. Wettability is a measure of a material's ability to absorb or repulse fluid on its surface. Smart materials whose wettability can be controlled have the potential to manipulate fluids at the micrometer scale. Such control can be achieved by altering the chemical composition of the surface, but this can be slow. Instead, Hong-Bo Sun and colleagues from Jilin University and co-workers have designed and fabricated a smart material in which the surface is changed using pneumatic micro-air-sacs. When a water droplet comes into contact with the inflated surface, it is captured and transferred to the desired location. Deflating the micro-air-sacs releases the droplet within a second. Smart surface with tunable properties is vital for modern intelligent applications. Here we demonstrate a novel surface that enables fast surface changing based on a bioinspired micro-air-sacs network. The pneumatic smart surface allows for rapid and large-amplitude topography deformation through pneumatic control, and permits dynamic wettability switching between dominant and latent states. A smart surface with contrastive rose-petal-like and lotus-leaf-like wetting characters is presented and utilized as a droplet manipulator for in situ capture and release of water droplets on demand.

Control and characterization of a bistable laminate generated with piezoelectricity

Abstract: Extensive research has been conducted on utilizing smart materials such as piezoelectric and shape memory alloy actuators to induce snap through of bistable structures for morphing applications. However, there has only been limited success in initiating snap through from both stable states due to the lack of actuation authority. A novel solution in the form of a piezoelectrically generated bistable laminate consisting of only macro fiber composites (MFC), allowing complete configuration control without any external assistance, is explored in detail here. Specifically, this paper presents the full analytical, computational, and experimental results of the laminate's design, geometry, bifurcation behavior, and snap through capability. By bonding two actuated MFCs in a [0MFC/90MFC]T layup and releasing the voltage post cure, piezoelectric strain anisotropy and the resulting in-plane residual stresses yield two statically stable states that are cylindrically shaped. The analytical model uses the Rayleigh–Ritz minimization of total potential energy and finite element analysis is implemented in MSC Nastran. The [0MFC/90MFC]T laminate is then manufactured and experimentally characterized for model validation. This paper demonstrates the adaptive laminate's unassisted forward and reverse snap through capability enabled by the efficiencies gained from simultaneously being the actuator and the primary structure.

Smart structures and actuators: past, present, and future

Abstract: The Defense Advanced Research Projects Agency (DARPA) currently supports several programs with a focus on smart materials and structures. Two of these programs, the Smart Materials and Structures Demonstration Program and the Compact Hybrid Actuators Program (CHAP), will be described and reviewed. The Smart Materials and Structures Demonstration projects aim to show the value of smart materials-based actuation systems in realistic applications. The CHAP efforts focus on the development of new types of useful electro-mechanical and chemo-mechanical actuators that exceed the specific power and power density of traditional electromagnetic and hydraulic-based actuation systems by a factor of ten for a range of applications. Outlined are the expected capabilities, significant technical challenges, and performance advantages foreseen in successful development and transition of the technologies targeted for exploration. The primary focus of the DARPA Smart Materials and Structures Demonstrations projects has been to apply existing smart materials in an appropriate device form to reduce noise and vibration and to achieve aerodynamic and hydrodynamic flow control in a variety of structures. Achievement of the program objectives will potentially create paradigm shifts for the design of undersea vehicles, helicopter rotor blades, aircraft wings, and engine inlets. Examples of these devices include small, high bandwidth devices for acoustic signature reduction; small, powerful actuators capable of fitting into the confined interior space of a rotating helicopter rotor blade for noise reduction; and flexible smart material driven control surfaces that will permit seamless and discrete span-wise shape changes for improved aerodynamic performance. Expected performance benefits are quantified and technical issues, especially those related to the smart materials and devices, will be identified and highlighted. In addition to the Smart Demos program, DARPA is sponsoring a new research effort entitled Compact Hybrid Actuator Program and several related SBIR topics. These projects focus on the development of electro-mechanical and chemo-mechanical actuators. In order to achieve efficiencies over those of electromagnetic actuators, these devices will take advantage of the high energy density of smart material transduction elements as well as innovative and efficient energy conversion of hydrocarbon fuels. These technologies include smart material-driven hydraulic systems, duty-cycle combustion systems, mechanically amplified systems, the control and drive electronics associated with these systems, as well as development efforts for magnetic shape memory alloys. The advantages of reduced volume, reduced power consumption and the high system reliability afforded by distributed actuation may allow compact hybrid actuation to supplant traditional actuation systems in many military and commercial platforms. It is for this reason that applications such as adaptive airframes, robotic locomotion, Unmanned Air Vehicles, and small-scale guided munitions have been targeted for transition.

Design of a smart material actuator for rotor control

Abstract: The results of a study to conceptually define an on-blade smart material actuator for primary and active control on a servoflap rotor are presented. Actuator design drivers, goals, and requirements are defined. For a previously developed hybrid actuator concept, the design of the cyclic and active (high speed) control actuator and feasibility of the collective (low speed) actuator and stroke multiplier are investigated. Sizing of actuator components based on AH-64 servoflap requirements shows that collective control using shape memory alloys is well within the capability of the material. Cyclic and active control using magnetostrictive material, leads to a reduced maneuver envelope due to weight and volume constraints. The promise of smart materials can be realized incrementally as the materials and actuator design approaches mature. Future improvements in smart material performance and actuator technology, and additional rotor system design changes to reduce load and motion requirements should provide the full AH-64 maneuver envelope.