About

H.C. (Sunny) Liu is a professor in the Department of Animal Science at North Carolina State University. He is affiliated with the Genetics and Genomics group, focusing on functional genomics within the field of animal science. His office is located in Polk Hall 232D, and he can be contacted via phone at 919-515-4024 or email at hc_liu@ncsu.edu. Dr. Liu's research and academic contributions are centered around genetics and genomics, with an emphasis on functional genomics, supporting advancements in animal science.

Research topics

• Optoelectronics
• Physics
• Materials science
• Optics
• Composite material
• Nanotechnology
• Computer Science
• Chemical engineering
• Telecommunications
• Structural engineering
• Engineering

Selected publications

• <i>In situ</i> imaging of domain walls in ferroelectric single crystals by instant polarized light microscopy

  Review of Scientific Instruments · 2026-03-01

  article

  Ferroelectric domain walls separate regions of uniform polarization in ferroelectric materials, and their controlled manipulation, such as through electric poling, is essential for enhancing the electromechanical performance of advanced ferroelectric devices. While most existing imaging techniques only examine static domain structures at the pre- or post-poling state, real-time, in situ, and non-destructive visualization of internal domain wall dynamics during electric poling using a simple implementation remains a significant challenge. In this work, we present a simple and accessible optical technique, instant polarized light microscopy (IPOLπ), for through-volume, single-shot, and in situ observation of domain wall evolution during electric poling. Demonstrated on [110]-oriented Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals, IPOLπ enables direct observation of polarization dynamics during alternating current poling and electrical depoling. The method reveals the formation of layered domain structures initiating at sample edges and progressing inward, as well as the correlation between optical birefringence changes and electrical current response. This low-cost, robust technique provides a powerful tool for studying real-time domain wall behavior, offering new insights into structure-property relationships in functional ferroelectric crystals.

  PublisherDOI

• Recent development in piezoelectric materials and devices for cryogenic environments

  Sensors and Actuators A Physical · 2025-02-14 · 12 citations

  article
  PublisherDOI

• Dielectric and piezoelectric properties of Mn-doped Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals with varying PbTiO3 content under alternate and direct current poling

  Journal of Applied Physics · 2025-04-22 · 5 citations

  articleOpen access

  This study investigated the dielectric and piezoelectric properties of third-generation Mn-doped Pb(In1/2Nb1/2)O3–Pb(Mg1/3Nb2/3)O3–PbTiO3 (Mn: PIN-PMN-PT) single crystals with varying PT content using alternating current poling (ACP) and direct current poling (DCP) at room temperature. Ten types of samples were taken sequentially from the top to the bottom of the crystal ingot, with Mn and PT content decreasing accordingly. The ACP method demonstrated the highest PT content sample on top, yielding a piezoelectric constant of (d33) 2280 pC/N, piezoelectric voltage constant (g33) of 41.8 × 10−3 Vm/N, and a dielectric constant (ε33T/ε0) of 6150, which are significantly higher (60% for d33, 84% for ε33T/ε0) than DCP single crystals. This type of single crystal exhibited a high coercive field (Ec) reaching 4.8 kV/cm. Additionally, the results indicate that ACP enhances the mechanical quality factor (Qm), achieving a value of 700. d33 and ε33T/ε0 of these two poling methods were examined from room temperature to beyond the Curie temperature. This study provided valuable insights into optimizing poling strategies to achieve enhanced performance for Mn: PIN-PMN-PT single crystal piezoelectric devices.

  PublisherDOI

• Dielectric and piezoelectric properties of prestressed Pb(Mg1/3Nb2/3)O3–PbTiO3 single crystals under alternating and direct current poling

  Applied Physics Letters · 2025-09-29

  article

  This study investigates the effect of prestress during the electric poling of [001]-cut Pb(Mg1/3Nb2/3)O3–PbTiO3 (PMN-PT) piezoelectric single crystals under both alternating current poling (ACP) and direct current poling (DCP). The samples were poled under various levels of mechanical stress and characterized via dielectric, piezoelectric, strain–electric field, and temperature-dependent measurements. It was found that samples poled via ACP with intermediate prestresses between 10 and 18 MPa showed an 8% and 10% increase in d33 and dielectric permittivity ε33T/ε0, respectively, compared to samples without prestress. At 18 MPa, the measured values of d33 and dielectric permittivity were 2470 pC/N and 8340, respectively, under ACP with a 15 kV/cm peak-to-peak electric field. In contrast, there was no obvious enhancement in the samples poled via DCP with prestress compared to without prestress. It was also found that prestress leads to increasing dielectric loss factors for the poled crystals under either ACP or DCP. The polarization loop data suggested that prestress can increase the coercive fields for ACP samples. Moreover, temperature-dependent experiments revealed that prestressed samples have significantly elevated dielectric constant and d33 at higher temperatures (above 93 °C). PFM scans showed that poling samples in the presence of prestress resulted in finer and more densely packed domains. These findings demonstrate that the combination of mechanical prestress and ACP poling can provide an effective route for engineering domain structures in PMN-PT single crystals suitable for advanced piezoelectric device applications.

  PublisherDOI

• Stacked PZT-CMUT hybrid 1D array for acoustic angiography: Preliminary results

  2025-09-15

  article

  In this work, we demonstrate the feasibility of a stacked PZT–CMUT array for acoustic angiography with separated transmit and receive bands. The system consists of a 1.9-MHz PZT-5A element bonded to a 64-element 1D CMUT array with a 6.4-MHz center frequency. CMUT’s borosilicate glass substrate serves as an acoustic matching layer for the piezoelectric transducer. Acoustic characterization was performed with a calibrated hydrophone at 22-mm depth, and in-vitro imaging was conducted using a tissue-mimicking phantom containing a 0.38-mm polyethylene tube at 22-mm depth. Microbubbles (2×10<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">8</sup> #/mL) were flowed at 120 µL/min, and received signals were high pass filtered above the third harmonic (>7.4 MHz). The PZT element generated 714 kPa peak-to-peak pressure with a mechanical index of 0.26, sufficient to induce microbubble resonance. A contrast-to-tissue ratio of 42.41 dB was achieved compared to 0.97 dB for water flow, demonstrating the potential of stacked PZT–CMUT arrays for frequency-separated acoustic angiography.

  PublisherDOI

• Enhanced domain dynamics in alternating current poled rhombohedral Pb(Mg _1/3 Nb _2/3 )O ₃ –PbTiO ₃ single crystals

  Journal of the American Ceramic Society · 2025-04-30 · 5 citations

  articleOpen access

  Abstract The understanding of domain dynamics in ferroelectric materials is crucial for optimizing their performance in piezoelectric and electro‐optic applications. Although previous studies have focused on static domain structures and macroscopic characteristics, the time‐resolved approach of domains remains largely unexplored. In this study, we compare the dynamic responses of direct current (DC) and alternating current (AC) poled [001]‐oriented rhombohedral Pb(Mg 1/3 Nb 2/3 )O 3 –PbTiO 3 (PMN–PT) single crystals using X‐ray photon correlation spectroscopy (XPCS) during the application of external electric fields. Our results demonstrate that the AC‐poled sample exhibit enhanced reconfiguration of domain variants in response to driving fields compared to the DC‐poled counterpart, as evidenced by accelerated correlation decay and faster relaxation time. This phenomenon is attributed to enhanced reversible domain wall motion achieved through AC poling, which facilitates field‐induced domain realignment. These findings provide insight into the relationship between dynamics and macroscopic properties in relaxor‐PT single crystals for high‐performance applications.

  PublisherOA PDFDOI

• Fabrication and anti-fouling performance assessment of micro-textured CNT-PDMS nanocomposites through the scalable roll-coating process

  Biofouling · 2024-11-25

  article

  diatom compared to the non-textured CNT-PDMS control samples.

  PublisherDOI

• Enhanced piezoelectrical properties of Pb(Zn_1/3Nb_2/3)O₃ - PbTiO₃ single crystals by AC poling

  Japanese Journal of Applied Physics · 2024-07-17 · 8 citations

  articleOpen access

  Abstract We investigated the effectiveness of AC poling (ACP) processes for [001] direction oriented Pb(Zn 1/3 Nb 2/3 )O 3 -0.055PbTiO 3 (PZN-PT) single crystals (SCs) and obtained a dielectric constant ε 33 T / ε 0 of 6680 and piezoelectric strain constant d 33 of 2760 pC/N, a piezoelectric charge constant g 33 of 46.7 × 10 −3 Vm/N, and a figure of merit (FOM) ( d 33 × g 33 ) of 129 × 10 −12 m 2 /N. These values were 19%, 31%, 10%, and 45% higher than those of DC poling PZN-PT SC, respectively. The phase change temperature T pc , Curie temperature T c , and acoustic impedance ( Z 33 ) of the ACP PZN-PT SC were 121 °C, 165 °C, and 30.5 MRayls, respectively. Compared with Pb(Mg 1/3 Nb 2/3 )O 3 −0.3PbTiO 3 SCs, the higher T pc , T c , and FOM and lower Z 33 of the PZN-PT SCs enable the applications in high temperature with superior Z 33 matching to water and human body than conventional Pb(Mg 1/3 Nb 2/3 )O 3 −0.3PbTiO 3 SCs , and these findings are vital for a wide range of ultrasonic transducer applications.

  PublisherDOI

• Electrical de-poling and re-poling of relaxor-PbTiO3 piezoelectric single crystals without heat treatment

  Nature Communications · 2024-07-30 · 12 citations

  articleOpen access

  Re-poling of unexpected partially depoled piezoelectric materials conventionally needs to be first fully depoled through annealing above their Curie temperature to revive piezoelectric performances. Here, we investigated de-poling and re-poling of Pb(In1/2Nb1/2)O3-Pb(Mg1/3Nb2/3)O3-PbTiO3 single crystals under electric fields at room temperature. We found that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to successfully depolarize poled crystals at room temperature. We also demonstrated a reversible polarization switching process with a relaxor-PbTiO3 single crystal ultrasound transducer without device performance degradations. This experimental observation is supported by phase-field simulation, showing that alternating current electric fields can readily induce de-poling at room temperature, while direct current electric fields induce a transient depoled state only within an uncontrollable short period of time. The findings suggest new strategies for unprecedented in-device tailoring of the polarization states of ferroelectric materials. The authors find that alternating current electric fields with amplitudes near the coercive field at low frequencies (<10 Hz) can be employed to depolarize poled relaxor-PbTiO3 single crystals at room temperature, without conventional heat treatment.

  PublisherOA PDFDOI

• Wearable Ultrasound Blood Pressure Monitoring System for Cardiovascular Health

  2024-09-22 · 1 citations

  article

  Hypertension is a major risk factor for cardiovascular disease, the leading cause of death globally. Continuous, non-invasive blood pressure monitoring is crucial for early detection, but existing methods struggle with real-time, wearable solutions. This study presents a wearable ultrasound (US) blood pressure monitoring (BPM) system that uses a compact PZT-5A transducer in a lightweight arm strap to track arterial diameter changes and generate blood pressure waveforms. In-vivo tests confirmed its accuracy in monitoring ulnar artery movements and correlating them with systolic and diastolic pressures. The system's advanced data processing techniques, including peak-tracking and noise reduction through moving average filters, ensure reliable blood pressure readings with 97.79% accuracy, making it a promising tool for real-time cardiovascular health monitoring.

  PublisherDOI

Frequent coauthors

• Jong Eun Ryu

  North Carolina State University

  24 shared

• Md Didarul Islam

  North Carolina State University

  11 shared

• Zahyun Ku

  Wright-Patterson Air Force Base

  9 shared

• John S. Derov

  United States Air Force Research Laboratory

  7 shared

• Darryl A. Boyd

  United States Naval Research Laboratory

  7 shared

• Jasbinder S. Sanghera

  United States Naval Research Laboratory

  7 shared

• Xiaoning Jiang

  North Carolina State University

  6 shared

• Michael Pudlo

  North Central State College

  6 shared

Labs

• H.C. (Sunny) Liu LabPI

  Not provided

Education

• Ph.D. student, Mechanical and aerospace engireering

  North Carolina State University

  2023

• Master, Mechanical and Aerospace Engineering

  North Carolina State University

  2020