Dr. Vivian Feig is an incoming Assistant Professor in the Mechanical Engineering department, beginning March 2024. The Feig lab aims to develop low-cost, noninvasive, and widely-accessible medical technologies that integrate seamlessly with the human body. We accomplish this by developing functional materials and devices with dynamic mechanical properties, leveraging chemistry and physics insights to engineer novel systems at multiple length scales. In pursuit of our goals, we maintain a strong emphasis on integrity and diversity, while nurturing the intellectual curiosity and holistic growth of our team members as researchers, communicators, and leaders.

Academic Appointments

All Publications

  • Drinkable in situ-forming tough hydrogels for gastrointestinal therapeutics. Nature materials Liu, G. W., Pickett, M. J., Kuosmanen, J. L., Ishida, K., Madani, W. A., White, G. N., Jenkins, J., Park, S., Feig, V. R., Jimenez, M., Karavasili, C., Lal, N. B., Murphy, M., Lopes, A., Morimoto, J., Fitzgerald, N., Cheah, J. H., Soule, C. K., Fabian, N., Hayward, A., Langer, R., Traverso, G. 2024


    Pills are a cornerstone of medicine but can be challenging to swallow. While liquid formulations are easier to ingest, they lack the capacity to localize therapeutics with excipients nor act as controlled release devices. Here we describe drug formulations based on liquid in situ-forming tough (LIFT) hydrogels that bridge the advantages of solid and liquid dosage forms. LIFT hydrogels form directly in the stomach through sequential ingestion of a crosslinker solution of calcium and dithiol crosslinkers, followed by a drug-containing polymer solution of alginate and four-arm poly(ethylene glycol)-maleimide. We show that LIFT hydrogels robustly form in the stomachs of live rats and pigs, and are mechanically tough, biocompatible and safely cleared after 24 h. LIFT hydrogels deliver a total drug dose comparable to unencapsulated drug in a controlled manner, and protect encapsulated therapeutic enzymes and bacteria from gastric acid-mediated deactivation. Overall, LIFT hydrogels may expand access to advanced therapeutics for patients with difficulty swallowing.

    View details for DOI 10.1038/s41563-024-01811-5

    View details for PubMedID 38413810

    View details for PubMedCentralID 5003561

  • Conducting polymer-based granular hydrogels for injectable 3D cell scaffolds. Advanced materials technologies Feig, V. R., Santhanam, S., McConnell, K. W., Liu, K., Azadian, M., Brunel, L. G., Huang, Z., Tran, H., George, P. M., Bao, Z. 2021; 6 (6)


    Injectable 3D cell scaffolds possessing both electrical conductivity and native tissue-level softness would provide a platform to leverage electric fields to manipulate stem cell behavior. Granular hydrogels, which combine jamming-induced elasticity with repeatable injectability, are versatile materials to easily encapsulate cells to form injectable 3D niches. In this work, we demonstrate that electrically conductive granular hydrogels can be fabricated via a simple method involving fragmentation of a bulk hydrogel made from the conducting polymer PEDOT:PSS. These granular conductors exhibit excellent shear-thinning and self-healing behavior, as well as record-high electrical conductivity for an injectable 3D scaffold material (~10 S m-1). Their granular microstructure also enables them to easily encapsulate induced pluripotent stem cell (iPSC)-derived neural progenitor cells, which were viable for at least 5 days within the injectable gel matrices. Finally, we demonstrate gel biocompatibility with minimal observed inflammatory response when injected into a rodent brain.

    View details for DOI 10.1002/admt.202100162

    View details for PubMedID 34179344

    View details for PubMedCentralID PMC8225239

  • Microengineering Pressure Sensor Active Layers for Improved Performance ADVANCED FUNCTIONAL MATERIALS Ruth, S., Feig, V., Tran, H., Bao, Z. 2020
  • Rational Design of Capacitive Pressure Sensors Based on Pyramidal Microstructures for Specialized Monitoring of Biosignals ADVANCED FUNCTIONAL MATERIALS Ruth, S., Beker, L., Tran, H., Feig, V., Matsuhisa, N., Bao, Z. 2020; 30 (29)
  • Biodegradable and stretchable polymeric materials for transient electronic devices MRS BULLETIN Liu, K., Tran, H., Feig, V., Bao, Z. 2020; 45 (2): 96–102
  • Electrochemical patterning of tissue-mimetic conductive hydrogels Feig, V., Tran, H., Lee, M., Liu, K., Huang, Z., Bao, Z. AMER CHEMICAL SOC. 2019
  • 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


    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

  • Strain- and Strain-Rate-Invariant Conductance in a Stretchable and Compressible 3D Conducting Polymer Foam MATTER Chen, G., Rastak, R., Wang, Y., Yan, H., Feig, V., Liu, Y., Jiang, Y., Chen, S., Lian, F., Molina-Lopez, F., Jin, L., Cui, K., Chung, J., Pop, E., Linder, C., Bao, Z. 2019; 1 (1): 205–18
  • 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
  • Multi-scale ordering in highly stretchable polymer semiconducting films NATURE MATERIALS Xu, J., Wu, H., Zhu, C., Ehrlich, A., Shaw, L., Nikolka, M., Wang, S., Molina-Lopez, F., Gu, X., Luo, S., Zhou, D., Kim, Y., Wang, G., Gu, K., Feig, V., Chen, S., Kim, Y., Katsumata, T., Zheng, Y., Yan, H., Chung, J., Lopez, J., Murmann, B., Bao, Z. 2019; 18 (6): 594-+
  • Multi-scale ordering in highly stretchable polymer semiconducting films. Nature materials Xu, J., Wu, H., Zhu, C., Ehrlich, A., Shaw, L., Nikolka, M., Wang, S., Molina-Lopez, F., Gu, X., Luo, S., Zhou, D., Kim, Y., Wang, G. N., Gu, K., Feig, V. R., Chen, S., Kim, Y., Katsumata, T., Zheng, Y., Yan, H., Chung, J. W., Lopez, J., Murmann, B., Bao, Z. 2019


    Stretchable semiconducting polymers have been developed as a key component to enable skin-like wearable electronics, but their electrical performance must be improved to enable more advanced functionalities. Here, we report a solution processing approach that can achieve multi-scale ordering and alignment of conjugated polymers in stretchable semiconductors to substantially improve their charge carrier mobility. Using solution shearing with a patterned microtrench coating blade, macroscale alignment of conjugated-polymer nanostructures was achieved along the charge transport direction. In conjunction, the nanoscale spatial confinement aligns chain conformation and promotes short-range pi-pi ordering, substantially reducing the energetic barrier for charge carrier transport. As a result, the mobilities of stretchable conjugated-polymer films have been enhanced up to threefold and maintained under a strain up to 100%. This method may also serve as the basis for large-area manufacturing of stretchable semiconducting films, as demonstrated by the roll-to-roll coating of metre-scale films.

    View details for PubMedID 30988452

  • 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
  • Stretchable and Fully Degradable Semiconductors for Transient Electronics. ACS central science Tran, H. n., Feig, V. R., Liu, K. n., Wu, H. C., Chen, R. n., Xu, J. n., Deisseroth, K. n., Bao, Z. n. 2019; 5 (11): 1884–91


    The next materials challenge in organic stretchable electronics is the development of a fully degradable semiconductor that maintains stable electrical performance under strain. Herein, we decouple the design of stretchability and transience by harmonizing polymer physics principles and molecular design in order to demonstrate for the first time a material that simultaneously possesses three disparate attributes: semiconductivity, intrinsic stretchability, and full degradability. We show that we can design acid-labile semiconducting polymers to appropriately phase segregate within a biodegradable elastomer, yielding semiconducting nanofibers that concurrently enable controlled transience and strain-independent transistor mobilities. Along with the future development of suitable conductors and device integration advances, we anticipate that these materials could be used to build fully biodegradable diagnostic or therapeutic devices that reside inside the body temporarily, or environmental monitors that are placed in the field and break down when they are no longer needed. This fully degradable semiconductor represents a promising advance toward developing multifunctional materials for skin-inspired electronic devices that can address previously inaccessible challenges and in turn create new technologies.

    View details for DOI 10.1021/acscentsci.9b00850

    View details for PubMedID 31807690

    View details for PubMedCentralID PMC6891860

  • 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


    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


    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

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


    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

  • Skin electronics from scalable fabrication of an intrinsically stretchable transistor array NATURE Wang, S., Xu, J., Wang, W., Wang, G., Rastak, R., Molina-Lopez, F., Chung, J., Niu, S., Feig, V. R., Lopez, J., Lei, T., Kwon, S., Kim, Y., Foudeh, A. M., Ehrlich, A., Gasperini, A., Yun, Y., Murmann, B., Tok, J., Bao, Z. 2018; 555 (7694): 83-+


    Skin-like electronics that can adhere seamlessly to human skin or within the body are highly desirable for applications such as health monitoring, medical treatment, medical implants and biological studies, and for technologies that include human-machine interfaces, soft robotics and augmented reality. Rendering such electronics soft and stretchable-like human skin-would make them more comfortable to wear, and, through increased contact area, would greatly enhance the fidelity of signals acquired from the skin. Structural engineering of rigid inorganic and organic devices has enabled circuit-level stretchability, but this requires sophisticated fabrication techniques and usually suffers from reduced densities of devices within an array. We reasoned that the desired parameters, such as higher mechanical deformability and robustness, improved skin compatibility and higher device density, could be provided by using intrinsically stretchable polymer materials instead. However, the production of intrinsically stretchable materials and devices is still largely in its infancy: such materials have been reported, but functional, intrinsically stretchable electronics have yet to be demonstrated owing to the lack of a scalable fabrication technology. Here we describe a fabrication process that enables high yield and uniformity from a variety of intrinsically stretchable electronic polymers. We demonstrate an intrinsically stretchable polymer transistor array with an unprecedented device density of 347 transistors per square centimetre. The transistors have an average charge-carrier mobility comparable to that of amorphous silicon, varying only slightly (within one order of magnitude) when subjected to 100 per cent strain for 1,000 cycles, without current-voltage hysteresis. Our transistor arrays thus constitute intrinsically stretchable skin electronics, and include an active matrix for sensory arrays, as well as analogue and digital circuit elements. Our process offers a general platform for incorporating other intrinsically stretchable polymer materials, enabling the fabrication of next-generation stretchable skin electronic devices.

    View details for PubMedID 29466334

  • The Effects of Counter Anions on the Dynamic Mechanical Response in Polymer Networks Crosslinked by Metal-Ligand Coordination JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY Rao, Y., Feig, V., Gu, X., Wang, G., Bao, Z. 2017; 55 (18): 3110–16

    View details for DOI 10.1002/pola.28675

    View details for Web of Science ID 000406937100029

  • Highly stretchable polymer semiconductor films through the nanoconfinement effect SCIENCE Xu, J., Wang, S., Wang, G. N., Zhu, C., Luo, S., Jin, L., Gu, X., Chen, S., Feig, V. R., To, J. W., Rondeau-Gagne, S., Park, J., Schroeder, B. C., Lu, C., Oh, J. Y., Wang, Y., Kim, Y., Yan, H., Sinclair, R., Zhou, D., Xue, G., Murmann, B., Linder, C., Cai, W., Tok, J. B., Chung, J. W., Bao, Z. 2017; 355 (6320): 59-?


    Soft and conformable wearable electronics require stretchable semiconductors, but existing ones typically sacrifice charge transport mobility to achieve stretchability. We explore a concept based on the nanoconfinement of polymers to substantially improve the stretchability of polymer semiconductors, without affecting charge transport mobility. The increased polymer chain dynamics under nanoconfinement significantly reduces the modulus of the conjugated polymer and largely delays the onset of crack formation under strain. As a result, our fabricated semiconducting film can be stretched up to 100% strain without affecting mobility, retaining values comparable to that of amorphous silicon. The fully stretchable transistors exhibit high biaxial stretchability with minimal change in on current even when poked with a sharp object. We demonstrate a skinlike finger-wearable driver for a light-emitting diode.

    View details for DOI 10.1126/science.aah4496

    View details for PubMedID 28059762

  • Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Rao, Y., Chortos, A., Pfattner, R., Lissel, F., Chiu, Y., Feig, V., Xu, J., Kurosawa, T., Gu, X., Wang, C., He, M., Chung, J. W., Bao, Z. 2016; 138 (18): 6020-6027


    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers.

    View details for DOI 10.1021/jacs.6b02428

    View details for Web of Science ID 000375889100044

    View details for PubMedID 27099162