On March 29, the latest issue of Science published a research article entitled "Biodegradable ferroelectric molecular crystal with large piezoelectric response" The team for the first time organically combined ferroelectrochemistry and bioelectronics, and innovatively developed a biodegradable organic ferroelectric crystal 2,2,3,3,4,4-hexafluoro-1,5-pentanediol (HFPD) with piezoelectric response directly chasing inorganic ceramic barium titanate (BTO), and its piezoelectric response d33 was 138 pC/N (Science 2024, 383). , 1492–1498）。 This was a major breakthrough since the discovery of the piezoelectric effect by the Curie brothers in 1880. Hanyue Zhang is the co-first author (ranked first) and co-corresponding author of the article, and Southeast University is the first corresponding unit.
With the continuous development of science and technology in mainland China, people's demand for medical health is increasing. Research into implantable piezoelectric biomedical devices is booming, which is expected to dramatically improve people's quality of life. Piezoelectric materials are a class of functional materials that can realize the mutual conversion of mechanical stress and electrical signals. At present, inorganic piezoelectric ceramics and piezoelectric polymers occupy the mainstream of applications, but they are not biodegradable, so implantable electronic devices made of traditional piezoelectric materials will face the risk of secondary surgical removal when applied to the human body. Therefore, implantable transient electronics based on biodegradable materials are expected to bring important changes to the medical field. These electronic devices are able to operate for a controlled period of time, dissolve in the body on their own, and do not produce toxic and harmful substances. Among them, natural piezoelectric biomaterials show many advantages in this regard. However, their piezoelectric properties are poor, and the piezoelectric coefficient d33 is mostly below 10 pC/N, which greatly limits their application in biomedicine. Molecular ferroelectric materials are expected to be ideal candidates for implantable transient electronic devices due to their unique advantages such as simple synthesis, easy processing, light weight, good biocompatibility and adjustable physical properties. Therefore, there is an urgent need to develop biodegradable molecular ferroelectric materials with high voltage properties.
Professor Xiong Rengen of Southeast University is the founder of the field of ferroelectrochemistry. Over the past decade, he has led a team focusing on the chemical design and research of molecular ferroelectric materials. This year, based on the hydrogen/fluorine substitution strategy and crystal engineering of ferroelectrochemistry, the team developed an organic small molecule ferroelectric with an infinitely long chain structure using a limited number of odd (n = 3)–CF2– groups in combination with hydrogen bond interactions (similar to bonds) to mimic the PVDF structure of phase b. The team reduced the structural units of PVDF from thousands to 3, and achieved a four-fold increase in the piezoelectric performance of small molecules (its piezoelectric response d33 is 138 pC/N), which played a role in four or two kilograms (Figure 1A).
This discovery brings the piezoelectric properties of implantable piezoelectric materials to new heights. The ferroelectric properties of this compound were systematically characterized by piezoelectric force microscopy (PFM) techniques and hysteresis loop testing (Figs. 1C and D). Its adjacent molecules pass through O–H··· O hydrogen bond interactions form a two-dimensional hydrogen bond network, a property that makes HFPD crystals easily soluble in a variety of solvents, especially body fluids, which facilitates the degradation of compounds in living organisms (Figure 1B). The compound has good biosafety, biocompatibility and biodegradability. Considering the brittleness and rigidity of the crystals, the team prepared HFPD-polyvinyl alcohol (PVA) flexible piezoelectric composite films with d33 of 34.3 pC/N by solution evaporation. Based on this piezoelectric composite film, the team also assembled a controllable transient electromechanical device and demonstrated good biosensing performance (Figs. 1E and F). This research provides promising candidate materials for degradable implantable electronic medical devices, as well as important applications for molecular piezoelectric materials that are closely related to human health.
Fig. 1.(A) Schematic diagram of design idea, (B) Structural stacking diagram, (C) Hysteresis loop, (D) "Return" shaped ferroelectric domain polarization flip, (E) Piezoelectric voltage output and image before and after degradation, (F) Schematic diagram of piezoelectric performance measurement of PLA-encapsulated HFPD-PVA device in SD rats and piezoelectric voltage output of the device in the knee joint region of rats.
Science审稿人对于该工作给予了高度评价，认为它是瞬态可植入压电材料领域里程碑式的关键突破（a key milestone for transient implantable piezoelectric materials）。 该工作还被《Science》以Perspectives的形式进行重点评述（Science 2024, 383, 1416），指出在铁电分子晶体中实现如此优异的压电性能是压电材料发展的一个里程碑(a milestone in piezoelectric material development)。
With the support of the National Natural Science Foundation of China and the "Top Ten Science and Technology Issues of Southeast University" Start-up Cultivation Fund, Dr. Hanyue Zhang's research interests are the chemical design of molecular ferroelectrics and their biomedical applications, with a focus on the research of organosilicon ferroelectrics. She is committed to the intersection of ferroelectrochemistry and biomedical applications around biomedical problems. Since working independently, the results have been published in Science, J. Am. Chem. Soc., Phys. Rev. Lett., Angew. Chem. Int. Ed. and other mainstream journals at home and abroad.
Zhang Hanyue (third from right) and some researchers in his team
Source: Southeast University, Dongda News Network
Editor-in-charge|Tian Haoyu
Proofreading|Yang Chen