AP Seminar - Engineering Electromechanical Coupling for Active Materials, Structures, and Devices

Electromechanical coupling is ubiquitous in nature and has profound implications for energy conversion, information processing, and biological processes. For example, strain is inevitably induced when electricity is stored in batteries or capacitors, and when ferroelectric field effect transistor is switched on and off for data storage. Focusing on recent works of my group in the past three years, in this talk we will illustrate the important effects of electromechanical coupling on active materials, structures, and devices, and how we can engineer it for novel functions. We first investigate dielectric polymers used in pulse discharge capacitors. The dielectric strength is critical for high power density, yet the breakdown failure is still poorly understood. Taking advantage of electromechanical coupling arising from Maxwell stress, we develop a novel technique to characterize the breakdown process in-situ based on digital image correlation, and we pin down the breakdown mechanism to the local electric field concentration [1,2]. Field induced creep is also observed, and we develop a modified Burgers model that accurately predicts long term creep behavior under either constant or cyclic voltage [3], which we believe will play an important role in analyzing aging and failure behaviors of dielectric polymers and capacitive devices. We then focus on flexoelectric engineering of dielectric membranes, which induces polarization via strain gradient in the otherwise centrosymmetric materials. We develop a von Karmon plate theory to account for the flexoelectric effect that is validated by piezoresponse force microcopy experiments on MoS₂ membrane [4], and we discover anomalously high Young’s modulus in freestanding PZT using machine learning empowered nanoindentation [5]. Flexoelectricity also enables mechanical switching of two-dimensional ferroelectric CuInP₂S₆ [6], which inspires us to develop novel mechanically gated transistor [7] and mechanically modulated photodetector [8]. We are living in an exciting era where the physical world meets big data, and active materials with electromechanical coupling are key enablers that can make the connection. Novel active materials, structures, and devices will continue to emerge, and exciting opportunities exist in electromechanical engineering for novel functions and optimal performances.

[1] Appl. Phys. Lett. 121, 243905 (2022)

[2] Appl. Phys. Lett. 123, 162901 (2023)

[3] J. Mech. Phys. Solids, under review.

[4] J. Mech. Phys. Solids 193, 105898 (2024)

[5] Adv. Mater. 37, 2412635 (2025)

[6] Sci. Adv. 8, eabq1232 (2022)

[7] Adv. Mater. 35, 2305766 (2023)

[8] Nano Letts. 24, 6337 (2024)