Lab profile: Zhenan Bao, Stanford University

New types of plastic that are conductive, stretchable, self-healing, and biodegradable–just like human skin–are on the horizon. Zhenan Bao has dedicated her career to the development of such innovative materials, which could offer a wealth of smart, revolutionary applications in electronics, medical devices, and a new generation of robotic and prosthetic devices.

Zhenan Bao is K.K. Lee Professor of Chemical Engineering and, by courtesy, a Professor of Chemistry and of Materials Science and Engineering at Stanford University. She also founded the Stanford Wearable Electronics Initiate (eWEAR) in 2016 and serves as the faculty director.

Prior to joining Stanford in 2004, Bao was a Distinguished Member of Technical Staff at Bell Labs, Lucent Technologies and received her PhD in Chemistry from the University of Chicago. She has over 700 publications and holds more than 100 US patents. With a Google Scholar H-Index >190, she is one of the Clarivate Citation Laureates. Bao is also a co-founder and on the Board of Directors of silicon-valley venture-funded start-ups C3 Nano and PyrAmes.

Bao is a member of the National Academy of Engineering, the American Academy of Arts and Sciences, the National Academy of Inventors, and is a foreign member of the Chinese Academy of Science. She was the inaugural recipient of the VinFuture Prize Female Innovator 2022 and has also received the ACS Chemistry of Materials Award 2022, the MRS Mid-Career Award and AICHE Alpha Chi Sigma Award in 2021, the ACS Central Science Disruptor and Innovator Prize and Gibbs Medal in 2020, the Wilhelm Exner Medal by Austrian Federal Minister of Science in 2018, and the ACS Award for Applied Polymer Science and the L'Oréal-UNESCO For Women in Science Award in the Physical Sciences in 2017.

Most recently, Bao has received the 2022 Materials Today Innovation Award, which recognizes leaders in materials science who have made advances in cutting-edge research that have opened a new, significant fields of research and resulted in impactful, practical applications.

Zhenan Bao talked to Materials Today about her current research and future plans.

How long has your group been running?

My group has been running since 2004.

How many staff currently makes up your group?

Currently the group has about 20 PhD students, close to 30 postdoctoral fellows, four undergraduate students, three Master’s students, six visiting scholars and one visiting student, a research staff member, and a lab manager.

What are the major themes of research in your group?

Our major themes of research are skin-inspired sensors and electronics, liquid and solid-state organic electrolytes, and polymer artificial solid-electrolyte interface layers for high-energy-density lithium metal batteries.

Our research focuses on a fundamental understanding of organic electronic material design with skin-like properties (flexible, stretchable, self-healing, and biodegradable) and enhanced electronic properties, patterning and fabrication of skin-like sensors, integrated circuits, displays and batteries. The main applications we investigate are related to precision human and mental health and enhanced human performance, which are enabled by the unique capabilities of the soft sensors and integrated circuits we have developed. Our insights into organic material design also allow us to design advanced electrolytes and polymer coatings rationally for more stable high-energy-density lithium metal batteries.

How and why did you come to work in these areas?

The core strength of my group is a deep knowledge of and foundation in organic and polymer chemistry in the area of molecular design for functional electronic devices. With our interests in addressing challenges that impact human health, we hypothesized that soft electronic sensors and integrated circuits with skin-like properties could fundamentally change the way humans interact with electronic devices. We believe skin-like electronics will reduce the gap between electronics and the human body to allow us to sense information relevant to human health directly. Since our health is regulated by both electrical and chemical signaling, the ability to monitor such information precisely throughout our body instead of at a single location will enable an unprecedented understanding of human health and eventually allow more effective disease interventions.

What facilities and equipment does your lab have?

We are equipped with facilities for organic synthesis, device fabrication, and characterization. We also benefit from the wonderful, shared facilities at Stanford for materials characterization and device fabrication. We also take advantage of the advanced X-ray characterization facilities in Stanford Linear Accelerator Center and several Department of Energy user facilities.

Do you have a favorite piece of kit or equipment?

I recently became a fan of the quantitative nanomechanics mode of atomic force microscopy as it provides a wealth of information about our materials at the nanometer scale.

What do you think has been your most influential work to date?

Our 2010 Nature Materials paper on the invention of a sensor based on microstructured rubber that mimics the human skin’s sense of touch marked the beginning of skin-inspired electronics. Our 2017 Science paper on nanoconfined polymer semiconductor was an important breakthrough for skin-inspired electronic materials as we discovered that nanoconfined polymer semiconductors overcome the long-standing challenge of a high-degree of disorder in polymer electronic materials. With this discovery, we have been able to incorporate skin-like properties into polymer semiconductors, conductors, and light-emitting polymers without degrading their electronic properties and even enhancing electronic performance. This finding will also help advance the electrical performance of polymer electronic materials in general.

With our understanding of skin-like electronic material design, we have also been able to develop scalable multi-step fabrication methods for large-scale integrated circuits. We are excited about a new generation of skin-like wearable and implantable electronic sensing systems and the new capabilities they will provide for precision health.

What is the key to running a successful group?

I believe the key is to establish a lab culture that encourages creativity, curiosity, and collaboration among lab members, along with mutual respect and support.

How do you plan to develop your group in the future?

I want to continue to encourage experimentation best practices to promote a good lab culture and provide the best environment for everyone to be successful and realize their highest potential.

Key publications

1. S. C. B. Mannsfeld, B. C. K. Tee, R. Stoltenberg, C. V. H. H. Chen, S. Barmann, B. V. O. Muir, A. N. Sokolov, C. Reese, Z. Bao. Highly sensitive flexible pressure sensors with microstructured rubber dielectric layers. Nature Materials 9 (2010) 859-864. https://doi.org/10.1038/nmat2834
2. D. J. Lipomi, M. Vosgueritchian, B. C-K. Tee, S. L. Hellstrom, J. A. Lee, C. H. Fox, and Z. Bao. Skin-Like Sensors of Pressure and Strain Enabled by Transparent, Elastic Films of Carbon Nanotubes. Nature Nanotechnology 6 (2011) 788-792. https://doi.org/10.1038/nnano.2011.184
3. B.C.K. Tee, A. Chortos, A. Berndt, A.K. Nguyen, A. Tom, A. McGuire, Z.C. Lin, K. Tien, W.-G. Bae, H. Wang, P. Mei, H.-H. Chou, B. Cui, K. Deisseroth, T. N. Ng, Z. Bao. A skin-inspired organic digital mechanoreceptor. Science 350 (2015) 313-316. https://science.org/doi/10.1126/science.aaa9306
4. J. Y. Oh, S. Rondeau-Gagné, Y.-C. Chiu, A. Chortos, F. Lissel, G.-J. N. Wang, B. C. Schroeder, T. Kurosawa, J. Lopez, T. Katsumata, J. Xu, C. Zhu, X. Gu, W.-G. Bae, Y. Kim, L. Jin, J. W. Chung, J. B.-H. Tok, Z. Bao. Intrinsically stretchable and healable semiconducting polymer for organic transistors. Nature 539 (2016) 411-415. https://doi.org/10.1038/nature20102
5. J. Xu, S. Wang, G.-J. N. Wang, C. Zhu, S. Luo, L. Jin, X. Gu, S. Chen, V. R. Feig, J. W. F. To, S. Rondeau-Gagné, J. Park, B. C. Schroeder, C. Lu, J. Y. Oh, Y. Wang, Y.-H. Kim, H. Yan, R. Sinclair, D. Zhou, G. Xue, B. Murmann, C. Linder, W. Cai, J. B.-H. Tok, J. W. Chung, Z. Bao. Highly stretchable polymer semiconductor films through the nanoconfinement effect. Science, 549 (2017) 59-64. https://www.science.org/doi/10.1126/science.aah4496
6. S. Wang, J. Xu, W. Wang, G.-J. N. Wang, R. Rastak, F. Molina-Lopez, J.W. Chung, S. Niu, V.R. Feig, J. Lopez, T. Lei, S.-K. Kwon, Y. Kim, A.M. Foudeh, A. Ehrlich, A. Gasperini, Y. Yun, B. Murmann, J.B.-H. Tok, Z. Bao. Skin Electronics from Scalable Fabrication of Intrinsically Stretchable Transistor Array. Nature, 555 (2018) 83-88. https://doi.org/10.1038/nature25494
7. Y.Q. Zheng, Y. Liu, D. Zhong, S. Nikzad, S. Liu, Z. Yu, D. Liu, H.C. Wu, C. Zhu, J. Li, H. Tran, J.B. Tok, Z. Bao. Monolithic optical microlithography of high-density elastic circuits. Science 373 (2021) 88-94. https://www.science.org/doi/10.1126/science.abh3551
8. Z. Zhang, W. Wang, Y. Jiang, Y.-X. Wang, Y. Wu, J.-C. Lai, S. Niu, C. Xu, C.-C. Shih, C. Wang, H. Yan, L. Galuska, N. Prine, H.-C. Wu, D. Zhong, G. Chen, N. Matsuhisa, Y. Zheng, Z. Yu, Y. Wang, R. Dauskardt, X. Gu. J. B.-H. Tok, Z. Bao. High-brightness all-polymer stretchable LED with charge-trapping dilution. Nature, 603 (2022) 624-630. https://doi.org/10.1038/s41586-022-04400-1
9. J. Li, Y. Liu, L. Yuan, B. Zhang, E.-S. Bishop, K. Wang, J. Tang, Y. Zheng, W. Xu, S. Niu, L. Beker, T.-L. Li, G. Chen, M. Diyaolu, A. Thomas, V. Mottini, J.-B. Tok, J.-C. Dunn, B. Cui, S.-P. Pa?ca, Y. Cui, A. Habtezion, X. Chen, Z. Bao. A tissue-like neurotransmitter sensor for the brain and gut. Nature, 606 (2022) 94-101. https://doi.org/10.1038/s41586-022-04615-2  
10. Y. Jiang, Z. Zhang, Y. X. Wang, D. Li, C.-T. Coen, E. Hwaun, G. Chen, H.-C. Wu, D. Zhong, S. Niu, W. Wang, J.-C. Lai, Y. Wu, Y. Wang, A. A. Trotsyuk, K. Y. Loh, C.-C. Shih, W. Xu, K. Liang, K. Zhang, Y. Bai, G. Gurusankar, W. Hu, W. Jia, Z. Cheng. R. Dauskardt, G. C. Gurtner, J. B.-H. Tok, K. Deisseroth, I. Soltesz, Z. Bao. Topological supramolecular network enabled high-conductivity, stretchable organic bioelectronics. Science 375 (2022) 1411-1417. https://www.science.org/doi/10.1126/science.abj7564