Many peptides and proteins have an innate ability to assemble into long, slender fibers called fibrils and other shapes. Now, researchers have found a way to harness this property to create tubular structures of diphenylalanine that have the ability to convert thermal energy into electrical energy, also called a pyroelectric effect.
Their results, published this week in Applied Physics Letters, from AIP Publishing, report that these nanoscale polymers, which are biocompatible, could have a wide range of biological applications such as for drug delivery scaffolds or miniature implantable sensors.
The team of researchers from Istanbul Technical University in Turkey, the University of Aveiro in Portugal, and Ural Federal University in Russia relied on diphenylalanine, a material they have previously studied for its unique electromechanical and physical properties. When drops of a solution of diphenylalanine are dried, peptide monomers form elongated hollow tubes that are structurally similar to the insoluble fibers formed by A? -amyloid peptide in Alzheimer’s disease.
“Diphenylalanine is one of the first self-assembling organic materials that can be used to make microscopic tubes, rods, ribbons, spheres and more,” said Andrei Kholkin, corresponding author on the study. “In the presence of water, its chemical groups self-organize to make noncovalent bonds and form amazingly rigid, cytoskeleton-like structures.”
The team of investigators dried a standard peptide solution for a day at room temperature to allow diphenylalanine to assemble into microtube structures, with individual tubes up to 1 millimeter long and 1-3 micrometer wide in diameter. To increase the current produced by the structures, the group created bundles of several microtubes and placed them between needle electrodes to measure the structures’ properties.
They heated the structures periodically with a laser, changed the temperature to reach approximately 80 degrees C and then calculated the pyroelectric coefficient, which is a measure of how effectively a material can convert heat into electric energy. Although the microtubes’ pyroelectric capacity was initially changeable — once heated and cooled, the coefficient decreased by ~30 percent — they remained stable after the first heating. The change may be because heating caused water molecules within the hollow tubes to become disordered, the authors suggest.
“This is the first observation of a significant pyroelectric effect in peptide microtubes similar to what’s seen with semiconductor materials such as zinc oxide or aluminum nitride,” Kholkin said. “In principle, our peptide nanotubes can be used in the same manner as these materials for various applications.”
In previous studies, the group has demonstrated that these nanotubes have piezoelectric effects — that is, they convert mechanical forces into electrical signals — and could be used as sensors for pacemakers or other small-scale electronic devices.
The newly discovered pyroelectric properties will broaden the potential uses for diphenylalanine microtubes, according to Kholkin. For example, the structures could be used to create small-scale thermal energy harvesters, which could scavenge energy lost in microelectronic devices. In addition, their pyroelectric properties could be used to engineer microscale and nanoscale thermometers that sense temperature variation, rather than the absolute temperature of a cell.
“Because these tubes can generate electricity under temperature and motion changes, they can be used to stimulate and monitor living cells,” Kholkin said.
Administratively, the teaching and research activities are distributed by Departments and Autonomous Sections, both with specialized faculties.
The University has more than 12,500 students distributed across 58 graduate courses, over 40 MSc courses and 25 PhD programs.
Its main campus is near the centre of Aveiro, including a nearby Administration and Accounting Institute. The university also has external regional campuses in Águeda, Higher Education Technological and Management School of Águeda, and Oliveira de Azeméis Higher Education School of North Aveiro.
It is an R&D university, having a research units developing programmes in fundamental and applied mathematics, physics, chemistry, telecommunications, robotics, bioinformatics, sea sciences, materials, design, business administration and industrial engineering.
Ground-breaking research has successfully created the world’s first truly electronic textile, using the wonder material Graphene
An international team of scientists, including Professor Monica Craciun from the University of Exeter, have pioneered a new technique to embed transparent, flexible graphene electrodes into fibres commonly associated with the textile industry.
The discovery could revolutionise the creation of wearable electronic devices, such as clothing containing computers, phones and MP3 players, which are lightweight, durable and easily transportable.
The international collaborative research, which includes experts from the Centre for Graphene Science at the University of Exeter, the Institute for Systems Engineering and Computers, Microsystems and Nanotechnology (INESC-MN) in Lisbon, the Universities of Lisbon and Aveiro in Portugal and the Belgian Textile Research Centre (CenTexBel), is published in the leading scientific journal Scientific Reports.
Professor Craciun, co-author of the research said: “This is a pivotal point in the future of wearable electronic devices. The potential has been there for a number of years, and transparent and flexible electrodes are already widely used in plastics and glass, for example. But this is the first example of a textile electrode being truly embedded in a yarn. The possibilities for its use are endless, including textile GPS systems, to biomedical monitoring, personal security or even communication tools for those who are sensory impaired. The only limits are really within our own imagination.”
At just one atom thick, graphene is the thinnest substance capable of conducting electricity. It is very flexible and is one of the strongest known materials. The race has been on for scientists and engineers to adapt graphene for the use in wearable electronic devices in recent years.
This new research has identified that ‘monolayer graphene’, which has exceptional electrical, mechanical and optical properties, make it a highly attractive proposition as a transparent electrode for applications in wearable electronics. In this work graphene was created by a growth method called chemical vapour deposition (CVD) onto copper foil, using a state-of-the-art nanoCVD system recently developed by Moorfield.
The collaborative team established a technique to transfer graphene from the copper foils to a polypropylene fibre already commonly used in the textile industry.
Dr Helena Alves who led the research team from INESC-MN and the University of Aveiro said: “The concept of wearable technology is emerging, but so far having fully textile-embedded transparent and flexible technology is currently non-existing. Therefore, the development of processes and engineering for the integration of graphene in textiles would give rise to a new universe of commercial applications. “
Dr Ana Neves, Associate Research Fellow in Prof Craciun’s team from Exeter’s Engineering Department and former postdoctoral researcher at INESC added: “We are surrounded by fabrics, the carpet floors in our homes or offices, the seats in our cars, and obviously all our garments and clothing accessories. The incorporation of electronic devices on fabrics would certainly be a game-changer in modern technology.
“All electronic devices need wiring, so the first issue to be address in this strategy is the development of conducting textile fibres while keeping the same aspect, comfort and lightness. The methodology that we have developed to prepare transparent and conductive textile fibres by coating them with graphene will now open way to the integration of electronic devices on these textile fibres.”
Dr Isabel De Schrijver,an expert of smart textiles fromCenTexBel said: “Successful manufacturing of wearable electronics has the potential for a disruptive technology with a wide array of potential new applications. We are very excited about the potential of this breakthrough and look forward to seeing where it can take the electronics industry in the future.”
Professor Saverio Russo, co-author and also from the University of Exeter, added: “This breakthrough will also nurture the birth of novel and transformative research directions benefitting a wide range of sectors ranging from defence to health care. “
First Proof of Ferroelectricity in Simplest Amino Acid
The boundary between electronics and biology is blurring with the first detection by researchers at Department of Energy’s Oak Ridge National Laboratory of ferroelectric properties in an amino acid called glycine.
A multi-institutional research team led by Andrei Kholkin of the University of Aveiro, Portugal, used a combination of experiments and modeling to identify and explain the presence of ferroelectricity, a property where materials switch their polarization when an electric field is applied, in the simplest known amino acid — glycine.
“The discovery of ferroelectricity opens new pathways to novel classes of bioelectronic logic and memory devices, where polarization switching is used to record and retrieve information in the form of ferroelectric domains,” said coauthor and senior scientist at ORNL’s Center for Nanophase Materials Sciences (CNMS) Sergei Kalinin.
Although certain biological molecules like glycine are known to be piezoelectric, a phenomenon in which materials respond to pressure by producing electricity, ferroelectricity is relatively rare in the realm of biology. Thus, scientists are still unclear about the potential applications of ferroelectric biomaterials.
“This research helps paves the way toward building memory devices made of molecules that already exist in our bodies,” Kholkin said.
For example, making use of the ability to switch polarization through tiny electric fields may help build nanorobots that can swim through human blood. Kalinin cautions that such nanotechnology is still a long way in the future.