Professional Education


  • Doctor of Philosophy, Columbia University (2016)
  • Master of Philosophy, Columbia University (2015)

Stanford Advisors


All Publications


  • An Electrochemical Gelation Method for Patterning Conductive PEDOT:PSS Hydrogels. Advanced materials (Deerfield Beach, Fla.) Feig, V. R., Tran, H., Lee, M., Liu, K., Huang, Z., Beker, L., Mackanic, D. G., Bao, Z. 2019: e1902869

    Abstract

    Due to their high water content and macroscopic connectivity, hydrogels made from the conducting polymer PEDOT:PSS are a promising platform from which to fabricate a wide range of porous conductive materials that are increasingly of interest in applications as varied as bioelectronics, regenerative medicine, and energy storage. Despite the promising properties of PEDOT:PSS-based porous materials, the ability to pattern PEDOT:PSS hydrogels is still required to enable their integration with multifunctional and multichannel electronic devices. In this work, a novel electrochemical gelation ("electrogelation") method is presented for rapidly patterning PEDOT:PSS hydrogels on any conductive template, including curved and 3D surfaces. High spatial resolution is achieved through use of a sacrificial metal layer to generate the hydrogel pattern, thereby enabling high-performance conducting hydrogels and aerogels with desirable material properties to be introduced into increasingly complex device architectures.

    View details for DOI 10.1002/adma.201902869

    View details for PubMedID 31414520

  • High-Transconductance Stretchable Transistors Achieved by Controlled Gold Microcrack Morphology ADVANCED ELECTRONIC MATERIALS Matsuhisa, N., Jiang, Y., Liu, Z., Chen, G., Wan, C., Kim, Y., Kang, J., Tran, H., Wu, H., You, I., Bao, Z., Chen, X. 2019; 5 (8)
  • Hierarchical patterns with sub-20 nm pattern fidelity via block copolymer self-assembly and soft nanotransfer printing POLYMER CHEMISTRY Tran, H., Bergman, H. M., Parenti, K. R., van der Zande, A. M., Dean, C. R., Campos, L. M. 2019; 10 (23): 3194–3200

    View details for DOI 10.1039/c9py00335e

    View details for Web of Science ID 000480561100029

  • Polymer Chemistries Underpinning Materials for Skin-Inspired Electronics MACROMOLECULES Tran, H., Feig, V. R., Liu, K., Zheng, Y., Bao, Z. 2019; 52 (11): 3965–74
  • Electrochemical patterning of tissue-mimetic conductive hydrogels Feig, V., Tran, H., Lee, M., Huang, R., Liu, K., Baker, L., Mackanic, D., Bao, Z. AMER CHEMICAL SOC. 2019
  • Designing a Quinone-Based Redox Mediator to Facilitate Li2S Oxidation in Li-S Batteries JOULE Tsao, Y., Lee, M., Miller, E. C., Gao, G., Park, J., Chen, S., Katsumata, T., Tran, H., Wang, L., Toney, M. F., Cui, Y., Bao, Z. 2019; 3 (3): 872–84
  • Biodegradable and flexible arterial-pulse sensor for the wireless monitoring of blood flow. Nature biomedical engineering Boutry, C. M., Beker, L., Kaizawa, Y., Vassos, C., Tran, H., Hinckley, A. C., Pfattner, R., Niu, S., Li, J., Claverie, J., Wang, Z., Chang, J., Fox, P. M., Bao, Z. 2019; 3 (1): 47–57

    Abstract

    The ability to monitor blood flow is critical to patient recovery and patient outcomes after complex reconstructive surgeries. Clinically available wired implantable monitoring technology requires careful fixation for accurate detection and needs to be removed after use. Here, we report the design of a pressure sensor, made entirely of biodegradable materials and based on fringe-field capacitor technology, for measuring arterial blood flow in both contact and non-contact modes. The sensor is operated wirelessly through inductive coupling, has minimal hysteresis, fast response times, excellent cycling stability, is highly robust, allows for easy mounting and eliminates the need for removal, thus reducing the risk of vessel trauma. We demonstrate the operation of the sensor with a custom-made artificial artery model and in vivo in rats. This technology may be advantageous in real-time post-operative monitoring of blood flow after reconstructive surgery.

    View details for PubMedID 30932072

  • Biodegradable and flexible arterial-pulse sensor for the wireless monitoring of blood flow NATURE BIOMEDICAL ENGINEERING Boutry, C. M., Beker, L., Kaizawa, Y., Vassos, C., Tran, H., Hinckley, A. C., Pfattner, R., Niu, S., Li, J., Claverie, J., Wang, Z., Chang, J., Fox, P. M., Bao, Z. 2019; 3 (1): 47–57
  • Mechanically tunable conductive interpenetrating network hydrogels that mimic the elastic moduli of biological tissue (vol 9, 2740, 2018) NATURE COMMUNICATIONS Feig, V. R., Tran, H., Lee, M., Bao, Z. 2018; 9: 5030

    Abstract

    The original version of this Article contained an error in the second sentence of the 'Materials' section of the Methods, which incorrectly read 'PEDOT:PSS synthesized by Orgacon (739324 Aldrich, MDL MFCD07371079) was purchased as a surfactant-free aqueous dispersion with 1.1 wt% solid content.' The correct version replaces this sentence with 'PEDOT:PSS Orgacon ICP 1050 was provided by Agfa as a surfactant-free aqueous dispersion with 1.1 wt% solid content.' This has been corrected in both the PDF and HTML versions of the Article.

    View details for PubMedID 30470738

  • Biodegradable and stretchable electronic materials for transient electronics Tran, H., Feig, V., Xu, J., Bao, Z. AMER CHEMICAL SOC. 2018
  • Mechanically tunable conductive interpenetrating network hydrogels that mimic the elastic moduli of biological tissue. Nature communications Feig, V. R., Tran, H., Lee, M., Bao, Z. 2018; 9 (1): 2740

    Abstract

    Conductive and stretchable materials that match the elastic moduli of biological tissue (0.5-500kPa) are desired for enhanced interfacial and mechanical stability. Compared with inorganic and dry polymeric conductors, hydrogels made with conducting polymers are promising soft electrode materials due to their high water content. Nevertheless, most conducting polymer-based hydrogels sacrifice electronic performance to obtain usefulmechanical properties. Here we report a method that overcomes this limitation using two interpenetrating hydrogel networks, one of which is formed by the gelation of the conducting polymer PEDOT:PSS. Due to the connectivity of the PEDOT:PSS network, conductivities up to 23Sm-1 are achieved, a record for stretchable PEDOT:PSS-based hydrogels. Meanwhile, the low concentration of PEDOT:PSS enables orthogonal control over the composite mechanical properties using a secondary polymer network. We demonstrate tunability of the elastic modulus over three biologically relevant orders of magnitude without compromising stretchability (>100%) or conductivity (>10Sm-1).

    View details for PubMedID 30013027

  • Skin-Inspired Electronics: An Emerging Paradigm ACCOUNTS OF CHEMICAL RESEARCH Wang, S., Oh, J., Xu, J., Tran, H., Bao, Z. 2018; 51 (5): 1033–45

    Abstract

    Future electronics will take on more important roles in people's lives. They need to allow more intimate contact with human beings to enable advanced health monitoring, disease detection, medical therapies, and human-machine interfacing. However, current electronics are rigid, nondegradable and cannot self-repair, while the human body is soft, dynamic, stretchable, biodegradable, and self-healing. Therefore, it is critical to develop a new class of electronic materials that incorporate skinlike properties, including stretchability for conformable integration, minimal discomfort and suppressed invasive reactions; self-healing for long-term durability under harsh mechanical conditions; and biodegradability for reducing environmental impact and obviating the need for secondary device removal for medical implants. These demands have fueled the development of a new generation of electronic materials, primarily composed of polymers and polymer composites with both high electrical performance and skinlike properties, and consequently led to a new paradigm of electronics, termed "skin-inspired electronics". This Account covers recent important advances in skin-inspired electronics, from basic material developments to device components and proof-of-concept demonstrations for integrated bioelectronics applications. To date, stretchability has been the most prominent focus in this field. In contrast to strain-engineering approaches that extrinsically impart stretchability into inorganic electronics, intrinsically stretchable materials provide a direct route to achieve higher mechanical robustness, higher device density, and scalable fabrication. The key is the introduction of strain-dissipation mechanisms into the material design, which has been realized through molecular engineering (e.g., soft molecular segments, dynamic bonds) and physical engineering (e.g., nanoconfinement effect, geometric design). The material design concepts have led to the successful demonstrations of stretchable conductors, semiconductors, and dielectrics without sacrificing their electrical performance. Employing such materials, innovative device design coupled with fabrication method development has enabled stretchable sensors and displays as input/output components and large-scale transistor arrays for circuits and active matrixes. Strategies to incorporate self-healing into electronic materials are the second focus of this Account. To date, dynamic intermolecular interactions have been the most effective approach for imparting self-healing properties onto polymeric electronic materials, which have been utilized to fabricate self-healing sensors and actuators. Moreover, biodegradability has emerged as an important feature in skin-inspired electronics. The incorporation of degradable moieties along the polymer backbone allows for degradable conducting polymers and the use of bioderived materials has led to the demonstration of biodegradable functional devices, such as sensors and transistors. Finally, we highlight examples of skin-inspired electronics for three major applications: prosthetic e-skins, wearable electronics, and implantable electronics.

    View details for PubMedID 29693379

  • Biodegradable Polymeric Materials in Degradable Electronic Devices ACS CENTRAL SCIENCE Feig, V. R., Tran, H., Bao, Z. 2018; 4 (3): 337–48

    Abstract

    Biodegradable electronics have great potential to reduce the environmental footprint of devices and enable advanced health monitoring and therapeutic technologies. Complex biodegradable electronics require biodegradable substrates, insulators, conductors, and semiconductors, all of which comprise the fundamental building blocks of devices. This review will survey recent trends in the strategies used to fabricate biodegradable forms of each of these components. Polymers that can disintegrate without full chemical breakdown (type I), as well as those that can be recycled into monomeric and oligomeric building blocks (type II), will be discussed. Type I degradation is typically achieved with engineering and material science based strategies, whereas type II degradation often requires deliberate synthetic approaches. Notably, unconventional degradable linkages capable of maintaining long-range conjugation have been relatively unexplored, yet may enable fully biodegradable conductors and semiconductors with uncompromised electrical properties. While substantial progress has been made in developing degradable device components, the electrical and mechanical properties of these materials must be improved before fully degradable complex electronics can be realized.

    View details for PubMedID 29632879

    View details for PubMedCentralID PMC5879474