Fangzhou Xia

@article{2023IEEESensors,

title = {A Doppler Radar with a Sweeping Lock-in Demodulator for Machine Vibration Sensing},

author = {Lois Wampler^ and Fangzhou Xia^* and Yip Fun Yeung and Takayuki Hirano and Ali Alshehri and Mikio Furokawa and Kamal Youcef-Toumi},

doi = {10.1109/JSEN.2023.3325820},

year  = {2023},

date = {2023-10-31},

urldate = {2023-10-31},

journal = {IEEE Sensors Journal},

abstract = {Data-driven predictive maintenance of modern machinery has the potential to increase equipment lifespan and decrease manufacturing costs. Vibration analysis can effectively diagnose potential problems in machines. A Doppler radar can be used as a sensor that provides non-contact, inexpensive real-time machine vibration data collection without necessitating line-down time. Implementation with Software Defined Radio (SDR) allow easy adjustment of excitation signals based on application needs. Conventional Fast Fourier Transformation based vibration analysis requires large amounts of data to achieve high spectral resolution needed for fault detection, which can be inefficient and computationally too expensive. In this work, we propose to use a sweeping lock-in amplifier to achieve high frequency resolution with small amounts of data by processing windowed sections of Doppler-shifted radio signals. This algorithm can reliably measure the Doppler shift frequency corresponding to the travelling speed of a moving object and identify the frequency of oscillating target with small amplitude, with the latter widely present in machine vibration. The distinguishing condition of the two cases is mathematically derived. The proposed algorithm is studied in simulation with triangular displacement waveform for simplicity of analysis and sinusoidal waveform for generic applications. For experimental verification, speaker vibration at a known frequency is analyzed to achieve an accuracy of 0.025 Hz within the known vibration frequency. This method is robust to the presence of noise frequencies and capable of detecting multiple frequencies.},

keywords = {Automation, Experimentation, Instrumentation, Mechatronics, Modeling & Simulation, Sensor, Signal Processing, Theory},

pubstate = {published},

tppubtype = {article}

}

@article{2023JoVE,

title = {Active Probe Atomic Force Microscopy with Quattro-Parallel Cantilever Arrays for High-Throughput Large-Scale Sample Inspection},

author = {Fangzhou Xia* and Kamal Youcef-Toumi and Thomas Sattel and Eberhard Manske and Ivo W. Rangelow},

url = {https://www.jove.com/t/65210},

doi = {10.3791/65210},

issn = {1940-087X},

year  = {2023},

date = {2023-06-16},

urldate = {2023-06-16},

journal = {Journal of Visualized Experiments},

pages = {e65210},

abstract = {An Atomic Force Microscope (AFM) is a powerful and versatile tool for nanoscale surface studies to capture 3D topography images of samples. However, due to their limited imaging throughput, AFMs have not been widely adopted for large-scale inspection purposes. Researchers have developed high-speed AFM systems to record dynamic process videos in chemical and biological reactions at tens of frames per second, at the cost of a small imaging area of up to several square micrometers. In contrast, inspecting large-scale nanofabricated structures, such as semiconductor wafers, requires nanoscale spatial resolution imaging of a static sample over hundreds of square centimeters with high productivity. Conventional AFMs use a single passive cantilever probe with an optical beam deflection system, which can only collect one pixel at a time during AFM imaging, resulting in low imaging throughput. This work utilizes an array of active cantilevers with embedded piezoresistive sensors and thermomechanical actuators, which allows simultaneous multi-cantilever operation in parallel operation for increased imaging throughput. When combined with large-range nano-positioners and proper control algorithms, each cantilever can be individually controlled to capture multiple AFM images. With data-driven post-processing algorithms, the images can be stitched together, and defect detection can be performed by comparing them to the desired geometry. This paper introduces principles of the custom AFM using the active cantilever arrays, followed by a discussion on practical experiment considerations for inspection applications. Selected example images of silicon calibration grating, highly-oriented pyrolytic graphite, and extreme ultraviolet lithography masks are captured using an array of four active cantilevers ("Quattro") with a 125 {textmu}m tip separation distance. With more engineering integration, this high-throughput, large-scale imaging tool can provide 3D metrological data for extreme ultraviolet (EUV) masks, chemical mechanical planarization (CMP) inspection, failure analysis, displays, thin-film step measurements, roughness measurement dies, and laser-engraved dry gas seal grooves.},

keywords = {Atomic Force Microscopy, Automation, Experimentation, Instrumentation, Material Science, Mechatronics, MEMS, Method, Sensor},

pubstate = {published},

tppubtype = {article}

}

@article{2023IEEETM,

title = {AFM SMILER: A Scale Model Interactive Learning Extended Reality Toolkit for Atomic Force Microscopy based on Digital Twin Technology},

author = {Fangzhou Xia* and Shane Lovet and Eyan Forsythe and Malek Ibrahim and Kamal Youcef-Toumi},

url = {https://ieeexplore.ieee.org/abstract/document/10136835},

doi = {10.1109/TMECH.2023.3274695},

year  = {2023},

date = {2023-06-01},

urldate = {2023-01-01},

journal = {IEEE Transactions on Mechatronics (in preparation)},

abstract = {Atomic force microscope (AFM) is a precision mechatronic system for nanoscale imaging of surfaces. Due to limited instrument access and lack of visualization techniques, understanding its principles can be challenging. Digital twin technology allows the creation of virtual representations of physical systems, which can be particularly useful to address challenges in AFM education. To realistically simulate nanoscale physics, we first developed new efficient algorithms for four virtual scale models, including cantilever mechanics, probe transducers, controller tuning, and contact mechanics. Second, three simulated experiment interactive learning modules are developed for instrument operation, including virtual imaging, system overview, and imaging modalities. In the end, three hardware systems are integrated for an extended reality experience, including a macroscopic AFM scale model, a haptic device for probe-sample interaction force feedback and an upgraded low-cost educational AFM for nanoscale imaging and instrumentation. This completes the eight total modules for the AFM SMILER: A Scale Model Interactive Learning Extended Reality toolkit. Preliminary studies shows the toolkit being helpful for AFM education. In addition to mechatronics and nanotechnology education, techniques developed in this work can be generally applied to computationally efficient realistic digital twin creation.},

keywords = {Atomic Force Microscopy, Design, Education, Experimentation, Instrumentation, Intelligence, Mechatronics, MEMS, Modeling & Simulation, Nanorobotics, Sensor, Theory},

pubstate = {published},

tppubtype = {article}

}

@article{2019NM,

title = {Lights Out! Nano-Scale Topography Imaging of Sample Surface in Opaque Liquid Environments with Coated Active Cantilever Probes},

author = {Fangzhou Xia* and Chen Yang and Yi Wang and Kamal Youcef-Toumi and Christoph Reuter and Tzvetan Ivanov and Mathias Holz and Ivo W Rangelow},

url = {https://www.mdpi.com/2079-4991/9/7/1013},

year  = {2019},

date = {2019-01-01},

urldate = {2019-01-01},

journal = {Nanomaterials},

volume = {9},

number = {7},

pages = {1013},

publisher = {Multidisciplinary Digital Publishing Institute},

abstract = {Atomic force microscopy is a powerful topography imaging method used widely in nanoscale metrology and manipulation. A conventional Atomic Force Microscope (AFM) utilizes an optical lever system typically composed of a laser source, lenses and a four quadrant photodetector to amplify and measure the deflection of the cantilever probe. This optical method for deflection sensing limits the capability of AFM to obtaining images in transparent environments only. In addition, tapping mode imaging in liquid environments with transparent sample chamber can be difficult for laser-probe alignment due to multiple different refraction indices of materials. Spurious structure resonance can be excited from piezo actuator excitation. Photothermal actuation resolves the resonance confusion but makes optical setup more complicated. In this paper, we present the design and fabrication method of coated active scanning probes with piezoresistive deflection sensing, thermomechanical actuation and thin photoresist polymer surface coating. The newly developed probes are capable of conducting topography imaging in opaque liquids without the need of an optical system. The selected coating can withstand harsh chemical environments with high acidity (e.g., 35% sulfuric acid). The probes are operated in various opaque liquid environments with a custom designed AFM system to demonstrate the imaging performance. The development of coated active probes opens up possibilities for observing samples in their native environments.},

keywords = {Atomic Force Microscopy, Experimentation, Instrumentation, Material Science, Mechatronics, MEMS, Nanorobotics, Sensor},

pubstate = {published},

tppubtype = {article}

}

@article{2017JVST,

title = {Active scanning probes: A versatile toolkit for fast imaging and emerging nanofabrication},

author = {Ivo W Rangelow* and Tzvetan Ivanov and Ahmad Ahmad and Marcus Kaestner and Claudia Lenk and Iman S Bozchalooi and Fangzhou Xia* and Kamal Youcef-Toumi and Mathias Holz and Alexander Reum},

url = {https://avs.scitation.org/doi/10.1116/1.4992073},

year  = {2017},

date = {2017-01-01},

urldate = {2017-01-01},

journal = {Journal of Vacuum Science & Technology B, Nanotechnology and Microelectronics: Materials, Processing, Measurement, and Phenomena},

volume = {35},

number = {6},

pages = {06G101},

publisher = {AVS},

abstract = {With the recent advances in the field of nanotechnology, measurement and manipulation requirements at the nanoscale have become more stringent than ever before. In atomic force microscopy, high-speed performance alone is not sufficient without considerations of other aspects of the measurement task, such as the feature aspect ratio, required range, or acceptable probe-sample interaction forces. In this paper, the authors discuss these requirements and the research directions that provide the highest potential in meeting them. The authors elaborate on the efforts toward the downsizing of self-sensed and self-actuated probes as well as on upscaling by active cantilever arrays. The authors present the fabrication process of active probes along with the tip customizations carried out targeting specific application fields. As promising application in scope of nanofabrication, field emission scanning probe lithography is introduced. The authors further discuss their control and design approach. Here, microactuators, e.g., multilayer microcantilevers, and macroactuators, e.g., flexure scanners, are combined in order to simultaneously meet both the range and speed requirements of a new generation of scanning probe microscopes.},

keywords = {Actuator, Atomic Force Microscopy, Instrumentation, MEMS, Nanorobotics, Review, Sensor},

pubstate = {published},

tppubtype = {article}

}