Discover Top Posts Tagged with #electromechanics

Researchers develop novel liquid metal circuits for flexible, self-healing wearables

Imagine a stretchable and durable sensor patch for monitoring the rehabilitation of patients with elbow or knee injuries, or an unbreakable and reliable wearable device that measures a runner's cardiac activities during training to prevent life-threatening injuries. Innovations in wearable technology are often limited by the electronic circuits—which are usually made of conductive metals that are either stiff or prone to damage—that power these smart devices. Researchers from the National University of Singapore (NUS) have recently invented a new super flexible, self-healing and highly conductive material suitable for stretchable electronic circuitry. This breakthrough could significantly improve the performance of wearable technologies, soft robotics, smart devices and more. The newly engineered material, called the Bilayer Liquid-Solid Conductor (BiLiSC), can stretch up to a remarkable 22 times its original length without sustaining a significant drop in its electrical conductivity. This electromechanical property, which has not been achieved before, enhances the comfort and effectiveness of the human-device interface, and opens a wide array of opportunities for its use in health care wearables and other applications.

A smart elastomer that can self-tune its stiffness and conductivity

Smart materials are materials that have the ability to change their properties in response to specific external stimuli, such as temperature, humidity, light, or applied stress. One of the most well-known examples of smart materials is shape memory alloy (SMA), which is a type of metallic material that can change its shape in response to changes in temperature.

Another example of smart materials includes piezoelectric materials, which generate an electric charge in response to applied mechanical stress. Smart materials have a wide range of potential applications, including in aerospace, automotive, robotics, manufacturing, and biomedical engineering.

Variable stiffness materials are a type of smart materials that have the ability to tune their stiffness, or resistance to deformation, in response to external stimuli. This property allows for the material to adapt to changing conditions and improve performance in a wide range of environments.

Researchers have synthesized a new material that solves one of the most difficult problems in the quest to create wearable, unobtrusive sensitive sensors: the problem of pressure.

A team of researchers, led by Trisha L. Andrew, professor of chemistry and chemical engineering at the University of Massachusetts Amherst, recently announced that they have synthesized a new material that solves one of the most difficult problems in the quest to create wearable, unobtrusive sensitive sensors: the problem of pressure.

"Imagine comfortable clothing that would monitor your body's movements and vital signs continuously, over long periods of time," says Andrew. "Such clothing would give clinicians fine-grained details for remote detection of disease or physiological issues." One way to get this information is with tiny electromechanical sensors that turn your body's movements -- such as the faint pulse you can feel when you place a hand on your chest -- into electrical signals. But what happens when you receive a hug or take a nap lying on your stomach? "That increased pressure overwhelms the sensor, interrupting the flow of data, and so the sensor becomes useless for monitoring natural phenomena," Andrew continues.

To solve this problem, the team developed a sensor that keeps working even when hugged, sat upon, leaned on or otherwise squished by everyday interactions. The secret, which was detailed in the journalAdvanced Materials Technologies, lies in vapor-printing clothing fabrics with piezoionic materials such as PEDOT-Cl (p-doped poly(3,4-ethylenedioxythiophene-chloride). With this method, even the smallest body movement, such as a heartbeat, leads to the redistribution of ions throughout the sensor. In other words, the fabric turns the mechanical motion of the body into an electrical signal, which can then be monitored.

Enhancing the electromechanical behavior of a flexible polymer

Piezoelectric materials convert mechanical stress into electricity, or vice versa, and can be useful in sensors, actuators and many other applications. But implementing piezoelectrics in polymers—materials composed of molecular chains and commonly used in plastics, drugs and more—can be difficult, according to Qiming Zhang, distinguished professor of electrical engineering.

Zhang and a Penn State-led team of interdisciplinary researchers developed a polymer with robust piezoelectric effectiveness, resulting in 60% more efficient electricity generation than previous iterations. They published their results today in Science.

"Historically, the electromechanics coupling of polymers has been very low," Zhang said. "We set out to improve this because the relative softness of polymers makes them excellent candidates for soft sensors and actuators in a variety of areas, including biosensing, sonar, artificial muscles and more."

To create the material, the researchers deliberately implemented chemical impurities into the polymer. This process, known as doping, allows researchers to tune the properties of a material to generate desirable effects—provided they integrate the correct number of impurities. Adding too little of a dopant could prevent the desired effect from initiating, while adding too much could introduce unwanted traits that hamper the material's function.

Enhancing piezoelectric properties under pressure

Stress enhances the properties of a promising material for future technologies.

UNSW researchers have found a new exotic state of one of the most promising multiferroic materials, with exciting implications for future technologies using these enhanced properties.

Combining a careful balance of thin-film strain, distortion and thickness, the team has stabilized a new intermediate phase in one of the few known room-temperature multiferroic materials.

The theoretical and experimental U.S.-Australian study shows that this new phase has an electromechanical figure of merit over double its usual value, and that we can even transform between this intermediate phase to other phases easily using an electric field.

Some materials can couple electrical and mechanical properties - this can lead to astonishing effects: New materials have been developed, consisting of both crystalline and amorphous regions. In these special polymers, the electro-mechanical coupling suddenly disappears - scientists have now found out how.

In certain materials, electrical and mechanical effects are closely linked: for example, the material may change its shape when an electrical field is applied or, conversely, an electrical field may be created when the material is deformed. Such electromechanically active materials are very important for many technical applications.

Usually, such materials are special, inorganic crystals, which are hard and brittle. For this reason, so-called ferroelectric polymers are now being used. They are characterised by the fact that their polymer chains exist simultaneously in two different microstructures: some areas are strongly ordered (crystalline), while disordered (amorphous) areas form in between. These semicrystalline composites are electromechanically active and therefore combine electrical and mechanical effects, but at the same time they are also flexible and soft. At TU Wien, such materials have now been studied in detail -- with surprising results: above a certain temperature, the properties change dramatically. A research team from TU Wien in cooperation with research groups from Madrid and London has now been able to explain why this happens.

From micro-sensors to smart textiles

"If you can control the mechanical behaviour of a material with the help of electric fields, you can use it to build tiny sensors, for example," says Prof. Ulrich Schmid from the Institute of Sensor and Actuator Systems at TU Wien. "This is also interesting for atomic force microscopes, where you set a tiny tip in vibration to scan a surface and generate an image."

Flipping the switch on ferroelectrics

Many next-generation electronic and electro-mechanical device technologies hinge on the development of ferroelectric materials. The unusual crystal structures of these materials have regions in their lattice, or domains, that behave like molecular switches. The alignment of a domain can be toggled by an electric field, which changes the position of atoms in the crystal and switches the polarization direction. These crystals are typically grown on supporting substrates that help to define and organize the behavior of domains. Control over the switching of domains when making crystals of ferroelectric materials is essential for any future applications.

Now an international team by Nagoya University has developed a new way of controlling the domain structure of ferroelectric materials, which could accelerate development of future electronic and electro-mechanical devices.

"We grew lead zirconate titanate films on different substrate types to induce different kinds of physical strain, and then selectively etched parts of the films to create nanorods," says lead author Tomoaki Yamada. "The domain structure of the nanorods was almost completely flipped compared with [that of] the thin film."

Researchers seek atomistic insights into ferroelectric materials

At first glance, biomedical imaging devices, cell phones, and radio telescopes may not seem to have much in common, but they are all examples of technologies that can benefit from certain types of relaxor ferroelectrics—ceramics that change their shape under the application of an electric field.

Electromechanical properties within these materials are strongest at specific combinations of temperature and applied electric fields. Two former postdoctoral researchers at the US Department of Energy's Oak Ridge National Laboratory (ORNL) are returning to their neutron sciences roots at the ORNL Spallation Neutron Source (SNS) to study this phenomenon.

Colleagues and frequent collaborators Abhijit Pramanick from the City University of Hong Kong and Mads Ry Jørgensen from Aarhus University in Denmark first met during the National School on Neutron and X-Ray Scattering (NXS) in 2008. Their latest project involves applying electric fields and varying temperatures to single-crystal samples using the TOPAZ instrument, SNS beam line 12, to examine how the material's atoms are displaced under those conditions. They say a better understanding of the material's behaviors should aid in the development of new relaxor ferroelectric designs with improved properties—and possibly ones that are more ecofriendly, too.

From micro-sensors to smart textiles

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