Carding: Selected Research Progress of Academician Bao Zhenan

Biography:

Bao Zhenan, female, was born in 1970 in Nanjing, China. She is a chemist, a member of the National Academy of Engineering, and a professor of chemical engineering at Stanford University. In 1987, Bao Zhenan was admitted to the Department of Chemistry of Nanjing University; in 1995 he entered the Bell Labs after receiving a doctorate degree in Chemistry from the University of Chicago in the United States; in 2001 he was awarded the title of Distinguished Researcher at the Bell Labs; Stanford University Female Teacher of Engineering Teaching Excellence Award; C3Nano, one of the founders at the end of 2010, was founded in Silicon Valley, USA; won the World Chinese Awards in 2011; was selected as one of the "Top Ten People of the Year" by Nature in 2015; Academician of the Academy of Engineering; won the World Outstanding Female Scientist Achievement Award in 2017.

The research scope of Academician Bao Zhenan‘s research group includes chemistry, materials science, energy, nanoelectronics and molecular electronics, organic and polymer semiconductor materials, sensing materials, organic semiconductor transistors, organic solar cells, electronic paper, and artificial electronic skin. Because of his great contribution in the field of artificial electronic skin, he is called the mother of "artificial electronic skin".

In order to facilitate everyone to quickly preview the scientific research results of Academician Bao Zhenan and his research team in recent years, the editors summarized the results publicized on the material source:

presented paper:

PNAS: conductive soft micro-pillar electrode array for biological electrophysiology recording

In Bao Zhenan Stanford University professor and Cui Xiao, associate professor will team (co-author) under the leadership, has developed a high conductivity, water stability, biocompatibility, similar to the biological tissue of the Young‘s modulus of the hydrogel: conductive Hydrogel (ECH). In this work, the team used the material to make a 3D, hydrogel-based soft microcolumn electrode array (ECH-MEAs) for single-cell, extracellular membrane electrophysiological recording. It was observed that the soft, soft micro-pillar electrodes flexed following the contraction-relaxation cycle of the cardiomyocytes, thereby minimizing any obstacle to the natural, rhythmic contraction of the cells. To prepare ECH-MEA, poly (3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT: PSS) ECH modified with an ionic liquid was used as an electrode material. Sixty ECH micropillars were lithographed into a pattern array, and each ECH micropillar had a diameter of 3 μm. Each microcolumn is independently addressable and connected to a multi-channel electrophysiological system via a printed circuit board. Related results were published on PANS under the title " Soft conductive micropillar electrode arrays for biologically relevant electrophysiological recording " .

Literature link: Soft conductive micropillar electrode arrays for biologically relevant electrophysiological recording (PANS, 2018, DOI: 10.1073 / pnas.1810827115)

Adv. Funct. Mater .: How to Have the Mechanical and Electronic Properties of Polymer Semiconductors

Professor Bao Zhenan (corresponding author) and Jaewan Mun (first author) of Stanford University published an article entitled Effect of Nonconjugated Spacers on Mechanical Properties of Semiconducting Polymers for Stretchable Transistors in the famous academic journal Adv. Funct. Mater. In this paper, three types of non-conjugated isolation segments with different degrees of flexibility and length are studied. It is found that longer and more non-conjugated isolation segments with higher flexibility can improve the toughness of polymer semiconductors and reduce the elastic modulus of polymer semiconductors. At the same time, the mobility of the polymer semiconductor is not greatly affected, and a fully stretchable transistor is prepared using the most suitable polymer semiconductor. The above results indicate that the introduction of non-conjugated isolation segments in conjugated polymers can effectively regulate mechanical properties without significantly sacrificing electronic properties.

Reference link : Effect of Nonconjugated Spacers on Mechanical Properties of Semiconducting Polymers for Stretchable Transistors ( Adv. Funct. Mater. 2018, DOI: 10.1002 / adfm.201804222 )

Nat. Nanotech .: Electronic Skin

August 20, 2018, the United States Stanford University ‘s Professor Bao Zhenan (corresponding author) and Donghee Son , Jiheong Kang and Orestis Vardoulis (co-first author) integrated in top international journals .. Nat Nanotech published an article on: An Integrated Self -healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network . This article reports that electronic skin devices that can monitor physiological signals and display feedback through closed-loop communication between users and electronic devices will be used in the next generation of wearables and the "Internet of Things." This device requires an ultra-thin construction to achieve seamless and conformal contact with the human body to accommodate strain from repetitive movements and to be comfortable to wear. Recently, self-healing chemistry has driven advances in deformable and reconfigurable electronics, particularly self-healing electrode systems. In previous studies, unlike polymer substrates with self-healing dynamic properties, damaged conductive networks cannot recover their stretchability after damage. Here, we report the self-reconstruction and self-repair of conductive nanostructures when in contact with a dynamically crosslinked polymer network. This, combined with the self-adhesive nature of self-healing polymers, allows the subsequent interconnection of heterogeneous multi-component devices of sensors and light-emitting devices into a single multifunctional system. This first self-healing and stretchable multi-component electronic skin paves the way for the development of powerful electronic devices in the future.

Article link: An integrated self-healable electronic skin system fabricated via dynamic reconstruction of a nanostructured conducting network. ( Nat. Nanotech. , DOI: 10.1038 / s41565-018-0244-6)

JACS: Quadruple hydrogen-bonded cross-linked supramolecular polymer film electrode material with stretchability, tear resistance, and self-healing

Bao Zhenan Fellow at Stanford University and Nanyang Technological University Daniel (co-author) research group in JACS published a report entitled the " Quadruple H-Bonding Supramolecular Cross-Linked Polymeric Materials for Stretchable Substrates AS, Antitearing, and Self-Healable Thin Film Electrodes " Article. The research team reports the de novo chemical design of a supramolecular polymer material by polycondensation, which consists of a soft polymer chain (polytetramethylene glycol and tetraethylene glycol) and a strong and reversible quadruple hydrogen bond crosslinker (0 to 30 mol%). The former helps form the soft areas of the SPM, while the latter provides the ideal mechanical properties for the SPM to produce soft, stretchable but tough elastomers. The obtained SPM-2 was observed to have high stretchability (up to 17000% strain), toughness (energy to break ~ 30000J / m ² ), and self-healing properties, which are very desirable properties and are superior to previously reported elasticity Body and strong hydrogel. In addition, the gold thin film electrode deposited on this SPM substrate maintains its conductivity and combines high stretchability (~ 400%), insensitivity to breaks / notches, self-healing, and good interfacial adhesion to the gold film. Again, these properties are highly complementary to commonly used polydimethylsiloxane-based thin-film metal electrodes. Finally, researchers continue to demonstrate the practical utility of the electrodes we make through in vivo and in vitro measurements of EMG signals. This basic understanding gained from investigating these SPMs will facilitate the development of smart soft materials and flexible electronics.

Literature link: Quadruple H-Bonding Cross-Linked Supramolecular Polymeric Materials as Substrates for Stretchable, Antitearing, and Self-Healable Thin Film Electrodes( JACS , 2018, DOI: 10.1021 / jacs.8b01682)

nature: skin-like electronic device based on an extensible fabrication process of an intrinsically stretchable transistor array

Stanford University Professor Bao Zhenan‘s research team developed a manufacturing process that can achieve high yield and uniform device performance for different intrinsically stretchable materials, and realized an intrinsically stretchable polymer transistor array with a transistor density of 347 / cm ² . It is the highest density of all flexible stretchable transistor arrays reported to date. The average carrier mobility of this array is comparable to that of amorphous silicon, and it has only slightly changed after 1000 times of 100% strain cycling tests. At the same time, it has no current-voltage hysteresis.

Based on the above manufacturing process, the team has developed for the first time skin-like stretchable integrated circuit components, such as stretchable tactile circuits integrated with active arrays and sensor arrays, which can adhere to the surface of human skin and allow flexible electronic devices to wear or More comfortable to use. The developed process provides a universal processing platform for combining with other inherently stretchable polymer materials, making it possible to manufacture the next generation of stretchable skin electronic devices.

Literature link: Skin electronics from scalable fabrication of an intrinsically stretchable transistor array (Nature, 2018, DOI: 10.1038 / nature25494)

Nature Energy: Tough, conductive, high-volume and high-area capacity 2D MOFs

From Professor Bao Zhenan Stanford University research group jointly Si Dege Ermo University and Argonne National Laboratory in the prestigious Nature publication sub- Nature Energy entitled the " Robust and Conductive Metal Organic TWO-dimensional volumetric frameworks with Exceptionally High Capacitance and Areal " Article. This article reports a method for designing a conductive MOF material with redox activity for use in supercapacitors. The capacity of this MOF is contributed by the pseudocapacitance rather than the electric double layer charge. In order to increase the redox active center, an ultra-small HAB (hexaaminobenzene) linker was selected to construct a conductive MOF. The HAB linker is consistent with the metal species of the d8 and d9 right-plane coordination geometry, resulting in sub-nanopores. This characteristic results in a high volume and large area capacitance that can be used in sub-millimeter thickness electrochemical capacitors.

Literature link: Robust and conductive two-dimensional metal organic frameworks with exceptionally high volumetric and areal capacitance (Nature Energy: 10.1038 / s41560-017-0044-5)

Adv. Energy Mater: Learn about the distribution of oligopolystyrene side chains on the performance of all-polymer solar cells

From Stanford University ‘s Professor Bao Zhenan (corresponding author) team at Advanced Eenergy Materials published an article entitled "on Understanding the Impact of Oligomeric Polystyrene Side Chain Arrangement on the All-Polymer Solar Cell Performance article", the paper reported the research team The latest research results on the influence of the molecular morphology of the polymer in the photosensitive layer on the performance of all-polymer solar cells. In this article, the introduction of oligopolystyrene (PS) side chains into the conjugated main chain has been shown to enhance the processability and electronic properties of semiconductor polymers. The researchers prepared two kinds of donor and acceptor polymers with different molar percentages of PS side chains to study and clarify the effect of their substitution distribution arrangement on the performance of all-polymer solar cells. When the PS side chain is substituted on the donor polymer, the performance of the battery device is observed to be lower, and when the PS side chain is substituted on the acceptor polymer, the performance of the battery device is observed to be higher. Studies have shown that the introduction of PS side chains into the acceptor polymer helps to reduce the size of phase-separated domains in the blended polymer films, however, the reduced domain size is still an order of magnitude larger than the typical exciton diffusion length. Detailed molecular morphology studies and estimates of the solubility parameters of the original PS, donor, and acceptor polymers show that the relative value of the solubility of each component mainly has a positive effect on the purity of the phase separation domain, which strongly affects the purity of the phase separation domain. The amount of photocurrent and the overall performance of the solar cell.

Literature link: Understanding the Impact of Oligomeric Polystyrene Side Chain Arrangement on the All-Polymer Solar Cell Performance (Adv. Energy Mater, 2017, DOI: 10.1002 / aenm.201701552)

PNAS: Application of biocompatible and fully decomposable semiconductor polymers in ultra-thin and ultra-light transient electronic devices

Professor Bao Zhenan (corresponding author) from Stanford University and others reported a biocompatible and fully decomposable semiconductor polymer and applied it to ultra-thin and ultra-light transient electronic devices. The topic "Biocompatible and totally disintegrable semiconducting polymer for ultrathin and ultralightweight transient electronics" was published on Proceedings of the National Academy of Sciences of the United States of America .

The semiconducting polymer studied in this paper is completely degradable and biocompatible, and can be used in thin film transistors. This polymer is connected by reversible imine bonds, and its constituents can be easily decomposed under mild acidic conditions. In addition, ultra-thin, biodegradable substrates with high chemical and thermal stability have also been developed. In combination with iron electrodes, fully degradable and biocompatible polymer transistors and pseudo-CMOS flexible circuits have also been successfully prepared. This kind of 赝 Complementary Metal Oxide Semiconductor Flexible Circuit has the characteristics of ultra-thin and ultra-light, its open circuit voltage is low, and it is expected to be used in low-cost, bio-compatible and ultra-light transient electronic devices. This article is an important advance in the field of organic materials and can be widely used in environmentally friendly and degradable electronic devices.

Literature link: Biocompatible and totally disintegrable semiconducting polymer for ultrathin and ultralightweight transient electronics (P. Natl. Acad. Sci. USA, 2017, DOI: 10.1073 / pnas.1701478114)

Science Advances: Highly malleable, transparent conductive polymer

Bao Zhenan (corresponding author) from Stanford University and others proposed a new method for obtaining highly ductile and conductive PEDOT thin films, which showed high cycle stability. The related research results were published in Science Advances on March 10, 2017 under the title " A highly stretchable, transparent, and conductive polymer " .

Previous major breakthroughs in ductile electronics have come from the study of strain engineering and nanocomposites. There are few reports on the study of molecular materials that are inherently ductile. In this paper, a highly ductile conductive polymer is studied. Its properties are achieved by combining with a series of reinforcing agents, which have dual functions: they can change the morphology and act as PEDOT: PSS (poly (3,4-ethylene Dioxythiophene): a conductivity-enhancing dopant in polystyrenesulfonic acid). Compared with the previously reported PEDOT: PSS with the best performance, the polymer film in the experiment has a conductivity of 3100S / cm at 0% strain and 4100 S / cm at 100% strain, which has been reported in ductile conductors. It has the highest conductivity. It can still maintain the conductivity of 3600S / cm after 1000 cycles under 100% strain. Under 600% strain, its conductivity can still maintain above 100S / cm. In addition, its breaking strain is as high as 800%, far exceeding the best silver nanowire and carbon nanotube-based ductile thin film. The combination of excellent electrical and mechanical properties enables it to be used as a medium for interconnection between field effect transistor arrays, which is five times higher than the density of devices under traditional lithographic wave interconnections.

Literature link: A highly stretchable, transparent, and conductive polymer (Sci. Adv., 2017, DOI: 10.1126 / sciadv.1602076)

Science: Highly stretchable polymer semiconductor film based on nano-confined region

Professor Bao Zhenan (corresponding author) of Stanford University and Jong Won Chung (corresponding author) of Samsung Advanced Technology Institute and others have explored the concept of polymer-based nano confinement to significantly improve the stretchability of polymer semiconductors without Affects charge transport mobility. Increased polymer chain dynamics under the nano-confinement significantly reduces the modulus of the conjugated polymer and greatly delays the initiation of crack formation under strain. Based on the above principles, the semiconductor film they prepared can be stretched to 100% strain without affecting the mobility and maintaining a value comparable to that of amorphous silicon. The fully stretchable transistors they showed exhibited high biaxial stretchability, and even when punctured with sharp objects, the change in on-state current was small, and they also showed a skin-like finger wearable LED driver.

Literature link: Highly stretchable polymer semiconductor films through the nanoconfinement effect (Science, 2017, DOI: 10.1126 / science.aah4496)

Nature: intrinsically stretchable and healable semiconductor polymer for organic transistors

Bao Zhenan (corresponding author) research group at Stanford University reported on November 17, 2016 a design of an intrinsically stretchable semiconductor polymer. The introduction of chemical groups promotes the dynamic non-covalent bonding of conjugated polymers. When strain occurs, these non-covalent cross-linked portions can undergo energy dissipation mechanisms by breaking bonds and maintain high electron mobility (over 1 cm ² V ⁻¹ s ⁻¹). The results show that the field-effect mobility of the semiconductor polymer can still maintain 1.12 cm ² V ⁻¹ s ⁻¹ under 100% strain .

Literature link: Intrinsically stretchable and healable semiconducting polymer for organic transistors (Nature, 2016, doi: 10.1038 / nature20102)

ACS Nano: Research on Limiting Factors of Scalable Full-Carbon Carbon Transistors in Scalable Electronic Device Applications

Professor Stanford University Professor Bao Zhenan (corresponding author) published an article " Investigating Limiting Factors in Stretchable All-Carbon Transistors for Reliable Stretchable Electronics "in ACS Nano . The researchers designed and constructed a retractable transistor consisting of a SWNT semiconductor electrode and a non-polar elastomer dielectric. The use of non-polar elastomer dielectric can effectively improve the hysteresis-free characteristics of the device. Compared with SiO ₂ dielectric devices, non-polar dielectric retractable devices exhibit lower mobility under ambient conditions because they are not doped with water. By using different SWNT sources as semiconductors, the effect of SWNT band gap on device characteristics is studied. Large band gap SWNTs exhibit well defects caused by the low capacitance of the dielectric. In contrast, SWNT high-current devices based on smaller band gaps are limited by contact resistance. Among all SWNT test sources, the SWNT retractable transistor with a maximum diameter of 1.5 nm has the best performance, its mobility is 15.4 cm ² / Vs, and the on / off ratio is> 10 ³ . Large band-gap devices have higher sensitivity to stress and depend on the thickness of the dielectric; while contact-limited devices clearly show less stress dependence.

Literature link: Investigating Limiting Factors in Stretchable All-Carbon Transistors for Reliable Stretchable Electronics (ACS Nano 2017, DOI: 10.1021 / acsnano.7b02458)

Adv. Funct. Mater .: Electric field regulation of the electrical properties of organic semiconductor films for molecular alignment and solution shear coating

From Stanford University Professor Bao Zhenan and Michael F. Toney Dr (Corporate Communication) and others to " Electric Field, the Tuning the Properties of Molecular Packing and Electrical‘s Solution-Shearing Coated Organic Semiconducting Thin Films " in the title in Advanced Functional Materials published an article on the study Regulation of electric field on molecular arrangement and electrical properties of solution-shear-coated organic semiconductor thin films.

Recent research progress in solution-coated organic semiconductors has proven its high application potential in the field of inexpensive organic electronic devices and sensors. The arrangement of the molecules directly determines the charge transfer in the solid. In the experiment, the electric field was used to control the crystal arrangement of the solution-sheared organic semiconductor. In the study, a theoretical model based on dielectrophoresis was first proposed to guide the selection of the optimal conditions (frequency and amplitude) of the electric field, and the optimal conditions were applied to the solution-shear-coated organic semiconductor film. Subsequently, a homogeneous polycrystal with both a human-shaped structure and a two-dimensional brick wall structure filling pattern was obtained. Experiments show that the optimal molecular arrangement has higher carrier mobility.

Literature link: Electric Field Tuning Molecular Packing and Electrical Properties of Solution-Shearing Coated Organic Semiconducting Thin Films (Adv. Funct. Mater., 2017, DOI: 10.1002 / adfm.201605503)

Review article:

Nature Materials Review: Exploration of Electronic Skin for Prosthetics

A review system entitled "Pursuing prosthetic electronic skin" published by Stanford University Professor Bao Zhenan (corresponding author) and others on Nature Materials introduces the material selection and electronic device design progress for mimicking skin perception and generating bionic signals. This review introduces the problems faced by the realization of artificial electronic skin through the study of the sensory and sensing mechanisms of real skin, the mechanical properties of flexible skin-like materials, how to shape the sensory function of the skin, the processing of sensory signal coding, and the mechanism of central nervous perception And conquering methods.

Literature link : Pursuing prosthetic electronic skin (Nature Materials, 2016, doi: 10.1038 / nmat4671)

Source of information: material cattle