About

Chingwen Cheng is the director of the Stuckeman School at Penn State University, having assumed the role on July 1, 2023. She previously served as the program head and associate professor of landscape architecture, urban design, and environmental design at the Design School at Arizona State University. Cheng is a climate justice design educator and advocate for climate actions through co-designing nature-based solutions with communities. Her research focuses on evaluating social-ecological landscape performance, sustainable and resilient urban water systems, and green infrastructure investment priorities, integrating theories of social vulnerability and environmental justice to develop frameworks such as the 'Climate Justicescape.' She has received significant research funding, including grants from the National Science Foundation and Wells Fargo Foundation, and has published extensively in high-impact journals. Cheng has also engaged with international research networks, chairing working groups related to urban resilience and climate justice, and serving on the steering committee for the APRU SCL research hub. She is a Registered Professional Landscape Architect and LEED-Accredited Professional with extensive experience in watershed planning, stormwater management, low-impact development, and community design in the United States. Her contributions include founding the Hydro-GI Lab, leading interdisciplinary collaborations, and actively participating in climate action initiatives within professional organizations.

Research topics

• Composite material
• Materials science
• Optoelectronics
• Optics
• Electronic engineering
• Acoustics
• Electrical engineering
• Physics

Selected publications

• Substrate dependence of the self-heating in lead zirconate titanate (PZT) MEMS actuators

  Journal of Applied Physics · 2024-04-23 · 1 citations

  articleOpen access

  Lead zirconate titanate (PZT) thin films offer advantages in microelectromechanical systems (MEMSs) including large motion, lower drive voltage, and high energy densities. Depending on the application, different substrates are sometimes required. Self-heating occurs in the PZT MEMS due to the energy loss from domain wall motion, which can degrade the device performance and reliability. In this work, the self-heating of PZT thin films on Si and glass and a film released from a substrate were investigated to understand the effect of substrates on the device temperature rise. Nano-particle assisted Raman thermometry was employed to quantify the operational temperature rise of these PZT actuators. The results were validated using a finite element thermal model, where the volumetric heat generation was experimentally determined from the hysteresis loss. While the volumetric heat generation of the PZT films on different substrates was similar, the PZT films on the Si substrate showed a minimal temperature rise due to the effective heat dissipation through the high thermal conductivity substrate. The temperature rise on the released structure is 6.8× higher than that on the glass substrates due to the absence of vertical heat dissipation. The experimental and modeling results show that the thin layer of residual Si remaining after etching plays a crucial role in mitigating the effect of device self-heating. The outcomes of this study suggest that high thermal conductivity passive elastic layers can be used as an effective thermal management solution for PZT-based MEMS actuators.

  PublisherOA PDFDOI

• Improving PMUT Receive Sensitivity via DC Bias and Piezoelectric Composition

  Sensors · 2022 · 16 citations

  1st authorCorresponding
  • Materials science
  • Acoustics
  • Optoelectronics

  increased 1.6 times, permittivity decreased by a factor of 0.6, and the voltage coefficient increased by ~2.5 times. For released PMUT devices, the ultrasound receive sensitivity improved by 2.5 times and the photoacoustic signal improved 1.9 times with 15 V applied DC bias. B-mode photoacoustic imaging experiments showed that with DC bias, the PMUT received clearer photoacoustic signals from pencil leads at 4.3 cm, compared to 3.7 cm without DC bias.

  PublisherOA PDFDOI

• Thermal stress accommodation in dip cast lead zirconate‐titanate ferroelectric films on flexible substrates

  Journal of the American Ceramic Society · 2022 · 7 citations

  • Materials science
  • Composite material
  • Optoelectronics

  Abstract Piezoelectric thin films were dip coat deposited onto flexible metal substrates to investigate the dependence of dielectric and ferroelectric properties on the coefficient of thermal expansion mismatch and substrate thickness. The bending stiffness was controlled by the thickness of the substrate. Grazing incidence X‐ray diffraction displayed distinct peak splitting for [Pb 0.98 ▪ 0.01 (Zr 0.52 Ti 0.48 )Nb 0.02 O 3 ] on flexible Pt, Ni, Ag, and stiff Ni substrates, where the out‐of‐plane d‐spacing and integrated peak area for c‐ domains were highest with the largest film compressive stress. As expected, lead zirconate titanate (PZT) films on stiff Si were under tensile stress and contained more in‐plane domains. The dielectric permittivity was highest in PZT on stiff Si and lowest for PZT on thick Ni, while remanent polarization displayed the opposite trend, commensurate with the residual stress state as well as the resistance to bending in thick substrates as a strain‐relief mechanism. The irreversible Rayleigh coefficient decreased dramatically upon poling for PZT on flexible substrates compared to PZT on stiff substrates; the ratio was 56% higher in PZT on a flexible Ni substrate relative to a stiff Ni substrate at 100 Hz prior to electrical poling. This investigation distinguishes the impact of substrate flexibility from thermal expansion on ferroelectric domain mobility and provides dip‐coating conditions for high‐quality piezoelectric films on any substrate.

  PublisherOA PDFDOI

• Cracking behavior in lead zirconate titanate films with different Zr/Ti ratios

  Applied Physics Letters · 2022 · 4 citations

  1st authorCorresponding
  • Materials science
  • Composite material
  • Optoelectronics

  Crack initiation stresses for different lead zirconate titanate (PZT) film compositions were investigated. PZT/Pt/TiO2/SiO2/Si stacks with 2.0 μm thick {100} oriented PZT films at the morphotropic phase boundary (MPB) showed a characteristic strength of 1137 MPa, and the film thickness served as the limiting flaw size for failure of the film/substrate stack. In contrast, for Zr/Ti ratios of 40/60 and 30/70, the characteristic stack strength increased while the Weibull modulus decreased to values typical for that of Si. This difference is believed to be due to toughening from ferroelasticity or phase switching. X-ray diffraction showed that the volume fraction of c-domains increased in Ti-rich compositions. This would allow for more switching from c to a-domains under biaxial tensile stress. Zr/Ti concentration gradients were present for all compositions, which contributed to the observation of a rhombohedral phase off the MPB. Due to the reduced tendency toward cracking, off-MPB compositions are potentially of interest in actuators, albeit with the trade-off of needing a high actuation voltage.

  PublisherOA PDFDOI

• Thin Film PZT-Based PMUT Arrays for Deterministic Particle Manipulation

  IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control · 2019-07-07 · 34 citations

  articleOpen access1st authorCorresponding

  Lead zirconate titanate (PZT)-based piezoelectric micromachined ultrasonic transducers (PMUTs) for particle manipulation applications were designed, fabricated, characterized, and tested. The PMUTs had a diaphragm diameter of 60 μm, a resonant frequency of ~8 MHz, and an operational bandwidth (BW) of 62.5%. Acoustic pressure output in water was 9.5 kPa at 7.5 mm distance from a PMUT element excited with a unipolar waveform at 5 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp.</sub> The element consisted of 20 diaphragms connected electrically in parallel. Particle trapping of 4 μm silica beads was shown to be possible with 5 V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> unipolar excitation. Trapping of multiple beads by a single element and deterministic control of particles via acoustophoresis without the assistance of microfluidic flow were demonstrated. It was found that the particles move toward diaphragm areas of highest pressure, in agreement with literature and simulations. Unique bead patterns were generated at different driving frequencies and were formed at frequencies up to 60 MHz, much higher than the operational BW. Levitation planes were generated above the 30 MHz driving frequency.

  PublisherOA PDFDOI

• Ring PMUT array based miniaturized photoacoustic endoscopy device

  Photons Plus Ultrasound: Imaging and Sensing 2019 · 2019-02-27 · 23 citations

  article

  The first successful validation of a forward-looking Piezoelectric Micromachined Ultrasound Transducer (PMUT) ring array designed for photoacoustic endoscopic imaging applications is presented. PMUT ring arrays were fabricated with a 0.5 mm inner diameter, to allow insertion of an optical fiber for light delivery, and ~2.5 mm overall outer diameter. Each ring array consisted of 6 elements, with a total of 102 PMUT cells, or 17 cells per element. Each PMUT cell has a 100 &mu;m diameter multi-layered diaphragm having a ~700 nm thick c-axis oriented aluminium nitride (AlN) thin film as the piezoelectric layer over a Si (handle layer) / SiO₂ (1 &mu;m) / Si (10 &mu;m) / SiO₂ (100 nm) / TiO₂ (40 nm) / Pt (150 nm) substrate to act as an ultrasound receive element. The resonant frequency was ~ 6 MHz in water. The output end of an optical fiber, coupled to a pulsed laser diode (PLD), was fitted with a 2.5 mm ferrule. The PMUT ring array was concentrically mounted on the ferrule to obtain a miniaturized endoscopic PAI device. The observed photoacoustic bandwidth was ~75%, and a strong photoacoustic signal of ~13 mV peak-to-peak output was observed from a light absorbing target kept 5 mm away from the PMUT array. 2D and 3D photoacoustic images of the targets were obtained via raster scanning of the phantom sample. In the future, the functionality of the PMUT ring array will be enhanced through multichannel acquisition to obtain variable acoustic focus and limited view photoacoustic images in real time.

  PublisherDOI

• A Photoacoustic Imaging Device Using Piezoelectric Micromachined Ultrasound Transducers (PMUTs)

  IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control · 2019-11-27 · 70 citations

  articleOpen access

  input. A receive sensitivity of ~0.48 mV/kPa was observed for a PMUT array element with 0 dB gain. The PMUT array was bonded to a custom-printed circuit board to enable compact integration with an optical fiber bundle for PAI. A broad photoacoustic bandwidth of ~89% was observed for the photoacoustic response captured from absorbing pencil lead targets. Linear scanning of a single element of a PMUT array was performed on different tissue phantoms embedded with light-absorbing targets to successfully demonstrate B-mode PAI using PMUTs.

  PublisherOA PDFDOI

• Multi-Channel Signal-Generator ASIC for Acoustic Holograms

  IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control · 2019-09-03 · 3 citations

  articleOpen access

  A complementary metal-oxide-semiconductor (CMOS) application-specific integrated circuit (ASIC) has been developed to generate arbitrary, dynamic phase patterns for acoustic hologram applications. An experimental prototype has been fabricated to demonstrate phase shaping. It comprises a cascadable 1 ×9 array of identical, independently controlled signal generators implemented in a 0.35- [Formula: see text] minimum-feature-size process. It can individually control the phase of a square wave on each of the nine output pads. The footprint of the integrated circuit is [Formula: see text]. A 128-MHz clock frequency is used to produce outputs at 8 MHz with a phase resolution of 16 levels (4 bits) per channel. A 6 ×6 air-coupled matrix array ultrasonic transducer was built and driven by four ASICs, with the help of commercial buffer amplifiers, for the application demonstration. Acoustic pressure mapping and particle manipulation were performed. In addition, a 2 ×2 array piezoelectric micromachined ultrasonic transducer (PMUT) was connected and driven by four output channels of a single ASIC, demonstrating the flexibility of the ASIC to work with different transducers and the potential for direct integration of CMOS and PMUTs.

  PublisherOA PDFDOI

• Effect of Titanium (Ti)-Seed and In Vacuo Process Flow on Sputtered Lead Zirconate Titanate Thin Films

  2019-09-01 · 1 citations

  article
  Publisher

• Evaluation of High Frequency Piezoelectric Micromachined Ultrasound Transducers for Photoacoustic Imaging

  2018-10-01 · 16 citations

  article

  In this work, the design, fabrication, and characterization of piezoelectric micromachined ultrasound transducer (PMUT) arrays for photoacoustic imaging applications are reported. An 80-element linear PMUT array with each element having 53 PMUT cells of 125 μm cell diameter were fabricated using 650 nm thick lead zirconate titanate (PZT) as the active piezoelectric layer. The PMUTs are designed to operate at ~10 MHz resonant frequency. The PMUT elements are validated for photoacoustic imaging using an agar gel phantom with embedded pencil leads as the imaging target. Photoacoustic A-line response of the targets captured by single PMUT element shows ~7 MHz center frequency with ~4.8 MHz bandwidth. B-mode images reconstructed from A-lines recorded during the linear scanning of a single element clearly imaged all the targets, thus validating the potential of the fabricated PMUTs for photoacoustic imaging.

  PublisherDOI

Frequent coauthors

• Susan Trolier‐McKinstry

  Pennsylvania State University

  10 shared

• Sri‐Rajasekhar Kothapalli

  Pennsylvania State University

  6 shared

• Ajay Dangi

  Pennsylvania State University

  5 shared

• Sumit Agrawal

  Pennsylvania State University

  5 shared

• Robert R. Benoit

  United States Army Combat Capabilities Development Command

  4 shared

• Rudra Pratap

  Narsee Monjee Institute of Management Studies

  4 shared

• Sudhanshu Tiwari

  4 shared

• Yongqiang Qiu

  3 shared

Labs

• Stuckeman SchoolPI

Awards & honors

• Knowledge Enterprise Honorable Mention (outstanding research…
• Diversity Virtual Travel Awards (mentor), 2021 IALE-North Am…
• U.S. EPA Campus RainWorks Challenge 2019, Second Place, Demo…
• Educator of the Year, Arizona Chapter American Society of La…
• Director’s Choice Award for Services, The Design School, Ari…