【Instrument research and development】Can mobile phones be bent at will like a thin film? Can the B-ultrasound machine be attached to the body to monitor the physical condition in real time? Can the sportswear worn on the body have an automatic power generation function? The breakthroughs made by the scientific research team and collaborators of Southeast University in the field of solving the piezoelectric properties of molecular materials have made the imagination in these science fiction films possible in the future.

Synthetic new molecular ferroelectric materials

On July 22, Southeast University held a press conference at the School of Chemistry and Chemical Engineering of Jiulonghu Campus and announced the latest research results - molecular ferroelectric materials with excellent piezoelectric properties. It was learned from the meeting that the synthesis of the material not only solves the problems that have restricted the development of molecular materials for 130 years, but also has many applications in the fields of sensors, human-computer interaction technology, and nanorobots in the future.

Piezoelectricity is the property that a material can generate electricity when it is extruded or stretched, or that the material elongates or shortens after two sections of the material are subjected to voltage. Piezoelectric materials are also called piezoelectric materials. Quartz watches used by people, medical ultrasound, and even the "shake" function of mobile phones are all applications of piezoelectric materials in real life.

At present, piezoelectric materials are mainly inorganic ceramics, but this material needs to be fired at high temperature, which has the disadvantages of not being able to form a film, poor flexibility, not environmentally friendly and cannot be recycled, and it is difficult to carry out miniaturized applications. Molecular materials can well compensate for these deficiencies of inorganic ceramic materials, but the piezoelectric properties of the former are far inferior to those of the latter.

Today, the new molecular ferroelectric materials synthesized by the team of Southeast University have reached the level of traditional piezoelectric ceramics in piezoelectric properties for the first time, and have all the advantages of molecular materials.

Professor You Yumeng, the leader of the research group, vividly explained the team's innovation in synthesis. "Piezoelectric materials are like sponges, and the water squeezed out of the sponge is like an electric current. The principle of traditional piezoelectric materials is equivalent to squeezing on both sides of the sponge, while our piezoelectric materials are equivalent to gently twisting and bending the sponge, so that a lot of electricity can be obtained under a small pressure. "

According to reports, since the Curie brothers discovered the piezoelectric effect on quartz single crystals in 1880, there has never been a case of molecular power generation material that can have such great piezoelectric performance.

Of course, there will be difficulties in the process of innovation.

You Yumeng said that in the nearly four-year research and development process, several doctors in the team only took three or four days off during the summer vacation and returned to the laboratory to do research. In addition to the challenges of design, synthesis, and testing, the biggest difficulty is how to make this new direction of molecular ferroelectric materials development recognized by inorganic materials researchers. "Because their (inorganic materials) research is very mature and already has their own set of standards, we hope that our new materials can also meet their standards and be recognized by them."

Sun Yueming, executive vice president of the Research Institute of Southeast University, commented that this achievement has established the leading position of the Southeast University team in the field of molecular ferroelectric research, and at the same time, the miniaturization application of molecular ferroelectric materials has broad prospects.

Professor You Yumeng said that new molecular ferroelectric materials can be applied to the miniaturization of large-scale medical equipment in the future. For example, "large equipment" such as blood pressure monitors and B-ultrasound machines are reduced and integrated into daily clothing to make "wearable" medical devices. In addition, new molecular ferroelectric materials can also play a role in human-computer interaction technology, microelectromechanical systems, aerospace and other fields.

However, he also said that it may take more than 10 years from the actual promotion to application in the laboratory, which requires not only technology, but also capital operation.

"A major breakthrough in the field of piezoelectric materials is like the first total fin fish coming ashore, which has brought our research in the field of piezoelectric materials from aquatic to terrestrial, and we see a vast unexplored new continent. There are many opportunities and more challenges on this continent. You Yumeng said, "We also hope that more researchers will join the research of molecular piezoelectric materials, and everyone will work together to make molecular piezoelectric materials bigger and better, so as to bring more convenience to people."

The team of Southeast University also cooperated with research teams from Nanjing University, Peking University, University of Washington and other universities. The research results were published online in Science on July 21, 2017. This paper is also an important achievement of the Jiangsu Provincial Key Laboratory of Molecular Ferroelectricity Science and Application.