Research

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Current Projects

Project: High-Speed ADC Design and Calibration for Wireline Communicaiton

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Project: Energy Efficient PLL for High-Speed Digital Communication

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Project: Wideband Data Converters for 5G/6G Wireless Communication

More details to be added.

Project: Electronic Neural Interfaces for Closed-loop Neuromodulation

More details to be added.

Journals

[J20] Y. Hou, Y. Zhu, J. Ji, A. G. Richardson, X. Liu, "A Wireless Sensor-Brain Interface System for Tracking and Guiding Animal Behaviors Through Closed-loop Neuromodulation in Water Mazes", IEEE Journal of Solid-State Circuits (JSSC), vol. 59, no. 4, Apr. 2024.
[J19] J. Xu, J. Filho, S. Nag, L. Long, E. Hwang, C. Tejeiro, G. O'Leary, Y. Huang, M. Kanchwala, M. Abdolrazzaghi, C. Tang, P. Liu, Y. Sui, H. You, X. Liu, J. Zariffa, R. Genov, "Fascicle-Selective Ultrasound-Powered Bidirectional Wireless Peripheral Nerve Interface IC," IEEE Transactions on Biomedical Circuits and Systems (TBioCAS), vol. 17, no. 6, pp. 1237-1256, Dec. 2023.
[J18] Y. Hou, J. Ji, Y. Zhu, T. Dell, and X. Liu, "Flexible Gel-Free Multi-Modal Wireless Sensors with Edge Deep Learning for Detecting and Alerting Freezing of Gait Symptom," IEEE Transactions on Biomedical Circuits and Systems (TBioCAS), vol. 17, no. 5, Oct. 2023.
[J17] H. Jafari, X. Liu, and R. Genov, "Synergistic Distributed Thermal Regulation for On-CMOS High-Throughput Multi-Modal Amperometric DNA-Array Analysis," IEEE Open Journal of Solid-State Circuits Society (OJ-SSCS), vol.3 pp. 89-102, Jan 2023.
[J16] N. Soltani, ..., X. Liu, and R. Genov, "A 21.3%-Efficiency Clipped-Sinusoid UWB Impulse Radio Transmitter with Simultaneous Inductive Powering and Data Receiving", IEEE Transactions on Biomedical Circuits and Systems (TBioCAS), vol. 16, no. 6, pp. 1228-1238, Nov. 2022.
[J15] Y. Ma, ... , X. Liu, and J. Van der Spiegel, "A Review of Electrochemical Electrodes and Readout Interface Designs for Biosensors", IEEE Open Journal of Solid-State Circuits Society (OJ-SSCS), vol. 3, pp. 76-88, Nov. 2022.
[J14] X. Liu, A. G. Richardson, "Edge deep learning for neural implants: a case study of seizure detection and prediction," Journal of Neural Engineering, vol. 18, no. 4, pp. 046034, Apr. 2021.
[J13] X. Liu, A. G. Richardson, and J. Van der Spiegel, "An Energy-efficient Compressed Sensing Based Encryption Scheme for Wireless Neural Recording", IEEE Journal on Emerging and Selected Topics in Circuits and Systems (JETCAS), vol. 11, no. 2, pp. 405-411, Apr. 2021.
[J12] M. Zhang, Z. Tang, X. Liu, J. Van der Spiegel, "Electronic Neural Interfaces," Nature Electronics, vol. 3, pp. 191–200, Mar. 2020.
[J11] X. Liu, H. Zhu, T. Qiu, S. Y. Sritharan, D. Ge, S. Yang, M. Zhang, A. G. Richardson, T. H. Lucas, N. Engheta, and J. Van der Spiegel, "A Fully Integrated Sensor-Brain-Machine Interface System for Restoring Somatosensation," IEEE Sensors Journal, vol. 21, no. 4, Oct. 2020.
[J10] A. G. Richardson, Y. Ghenbot, X. Liu, H. Hao, C. Rinehart, S. DeLuccia, S. Torres Maldonado, G. Boyek, M. Zhang, F. Aflatouni, J. Van der Spiegel, and Timothy H. Lucas, "Learning active sensing strategies using a sensory brain–machine interface," Proceedings of the National Academy of Sciences (PNAS), vol. 116, no. 35, Aug. 2019.
[J9] X. Liu, M. Zhang, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "Design of a Closed-loop, Bi-directional Brain Machine Interface System with Energy Efficient Neural Feature Extraction and PID control," IEEE Transactions on Biomedical Circuits and Systems (TBioCAS), vol. 11, no. 4, pp. 729-742, Aug. 2017.
[J8] A. G. Richardson, X. Liu, P. K. Weigand, E. D. Hudgins, J. M. Stein, S. R. Das, A. Proekt, M. B. Kelz, M. Zhang, J. Van der Spiegel, T. H. Lucas. "Hippocampal gamma‐slow oscillation coupling in macaques during sedation and sleep," Hippocampus, vol. 27, no. 11, Jan. 2017.
[J7] T. H. Lucas, X. Liu, M. Zhang, S. Sritharan, I. Planell-Mendez, Y. Ghenbot, S. Torres-Maldonado, C. Brandon, J. Van der Spiegel, A. G. Richardson, "Strategies for Autonomous Sensor–Brain Interfaces for Closed-Loop Sensory Reanimation of Paralyzed Limbs," Neurosurgery, vol. 64, pp. 11-20, Sept. 2017.
[J6] X. Liu, M. Zhang, T. Xiong, A. G. Richardson, T. H. Lucas, P. S. Chin, R. Etienne-Cummings, T. D. Tran, and J. Van der Spiegel, "A Fully Integrated Wireless Compressed Sensing Neural Signal Acquisition System for Chronic Recording and Brain Machine Interface," IEEE Transactions on Biomedical Circuits and Systems (TBioCAS), vol. 10, No. 4, Aug. 2016.
[J5] X. Liu, J. Sacks, M. Zhang, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "The Virtual Trackpad: an Electromyography-based, Wireless, Real-time, Low-Power, Embedded Hand Gesture Recognition System using an Event-driven Artificial Neural Network," IEEE Transactions on Circuits and Systems II: Express Briefs (TCAS-II), vol. 64, no. 11, Dec. 2016.
[J4] A. G. Richardson, M. A. Attiaha, J. I. Bermanb, H. I. Chena, X. Liu, M. Zhang, J. Van der Spiegel, T.H. Lucas, "The effects of acute cortical somatosensory deafferentation on grip force control," Cortex, vol. 74, pp. 1-8, Jan. 2016.
[J3] X. Liu, M. Zhang, B. Subei, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "The PennBMBI: Design of a General Purpose Wireless Brain-Machine-Brain Interface System," IEEE Transaction on Biomedical Circuits and System (TBioCAS), vol. 9, no. 2, pp. 248-258, 2015.
[J2] X. Wu, X. Liu, M. Zhang, J. Van der Spiegel, "Current Mode Image Sensor With Improved Linearity and Fixed Pattern Noise," IEEE Transactions on Circuits and Systems I: Regular Papers (TCAS-I), vol. 61, no. 6, pp. 1666-1674, Jun. 2014.
[J1] X. Liu, M. Zhang, J. Van der Spiegel, "A Low-Power Multifunctional CMOS Sensor Node for an Electronic Facade," IEEE Transactions on Circuits and Systems I: Regular Papers (TCAS-I), vol. 61, no. 9, pp. 2550-2559, Sept. 2014.

Conferences

[C26] J. S. Filho, H. Kassiri, X. Liu, and R. Genov, "Artificially Intelligent Closed-Loop Neurostimulators: Trade-offs Between Local and Remote Computing," IEEE Custom Integrated Circuits Conference (CICC), Apr. 2024.
[C25] Y. Hou, Y. Zhu, X. Wu, Y. Li, T. H. Lucas, A. G. Richardson, and X. Liu, "A Multi-Loop Neuromodulation Chipset Network with Frequency-Interleaving Front-End and Explainable AI for Memory Studies in Freely Behaving Monkeys," International Solid-State Circuits Conference (ISSCC), Feb. 2024.
[C24] S. Blade, Z. Yao, Y. Hou, Y. Li, S. Zhou, Y. Wang, and X. Liu, "An sEMG-Controlled Prosthetic Hand Featuring a Tiny CNN-Transformer Model and Force Feedback", IEEE Biomedical Circuits and Systems Conference (BioCAS), Oct. 2023.
[C23] Y. Zhu, Y. Hou, J. Ji, A. Zhou, A. G. Richardson, and X. Liu, "A Wireless Sensor-Brain Interface System for Tracking and Guiding Animal Behaviors Through Goal-Directed Closed-loop Neuromodulation", IEEE Symposium on VLSI Technology and Circuits (VLSI), Kyoto, Japan, Jun. 2023.
[C22] V. Kang, A. Malak, K. Lau, Y. Zhu, C. Morshead, and X. Liu, "A 0.9 g Battery-Free Wireless Stimulator with Infrared Communication for Applications in Neural Repair and Regeneration", IEEE International Symposium on Circuits and Systems (ISCAS), Monterey, CA, USA, May 2023.
[C21] M. Sun, A. Zhou, N. Yang, Y. Xu, Y. Hou, A.G. Richardson, and X. Liu, "Design of a Sleep Modulation System with FPGA-Accelerated Deep Learning for Closed-Loop Stage-Specific In-Phase Auditory Stimulation", IEEE International Symposium on Circuits and Systems (ISCAS), Monterey, CA, USA, May 2023.
[C20] M. Wagih Ismail, X. Liu, and T. Chan Carusone, "Inductorless Bandpass Noise-Shaping Continuous-Time Pipelined ADC Architectures", IEEE International Symposium on Circuits and Systems (ISCAS), Monterey, CA, USA, May 2023.
[C19] T. Yu, B. Cui, Y. Xu, and X. Liu, "Refine EEG Spectrogram Synthesized by Generative Adversarial Network For Improving the Prediction of Epileptic Seizures", IEEE International EMBS Conference on Neural Engineering (NER), 2023.
[C18] Z. Yao, and X. Liu, "A CNN-Transformer Deep Learning Model for Real-time Sleep Stage Classification in an Energy-Constrained Wireless Device", IEEE International EMBS Conference on Neural Engineering (NER), 2023.
[C17] O. Lin, T. Yu, Y. Hou, Y. Zhu, and X. Liu, "Wireless Sensors with Edge Deep Learning for Detecting and Alerting Freezing of Gait Symptoms in Parkinson's Pastients", IEEE International EMBS Conference on Neural Engineering (NER), 2023.
[C16] J. Xu, et al., "Fascicle-Selective Bidirectional Peripheral Nerve Interface IC with 173dB FOM Noise-Shaping SAR ADCs and 1.38 pJ/bit Frequency-Multiplying Current-Ripple Radio Transmitter", International Solid-State Circuits Conference (ISSCC), 2023.
[C15] Z. Chen, H. Wang, C. Yeh, and X. Liu, "Classify Respiratory Abnormality in Lung Sounds Using STFT and a Fine-Tuned ResNet18 Network," IEEE Biomedical Circuits and Systems Conference (BioCAS), Oct. 2022.
[C14] X. Liu, and A. G. Richardson, "A System-on-Chip for Closed-loop Optogenetic Sleep Modulation," International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Nov. 2021.
[C13] P. Unegbu, X. Liu, and F. Vitale, "Design and Testing of a Closed-Loop Neurochemical Modulator," Abstract, International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Nov. 2021.
[C12] X. Liu, M. Zhang, H. Hao, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "Wireless Sensor Brain Machine Interfaces for Closed-loop Neuroscience Studies," IEEE International Conference on ASIC (ASICON), Oct 2019.
[C11] X. Liu, H. Zhu, M. Zhang, X. Wu, A. G. Richardson, S. Y. Sritharan, D. Ge, Y. Shu, T. H. Lucas, and J. Van der Spiegel, "A Fully Integrated Wireless Sensor-Brain Interface System to Restore Finger Sensation", Circuits and Systems, IEEE International Symposium on (ISCAS), May 2017.
[C10] X. Liu, H. Zhu, M. Zhang, X. Wu, A. G. Richardson, S. Y. Sritharan, D. Ge, Y. Shu, T. H. Lucas, and J. Van der Spiegel, "A Wireless Neuroprosthetic for Augmenting Perception Through Modulated Electrical Stimulation of Somatosensory Cortex," IEEE International Symposium on Circuits and Systems (ISCAS), May 2017.
[C9] J. Van der Spiegel, M. Zhang, and X. Liu, "The next-generation brain machine interface system for neuroscience research and neuroprosthetics development," IEEE International Conference on ASIC (ASICON), 2017.
[C8] S. Sritharan, A. Richardson, P. Weigand, I. Planell-Mendez, X. Liu, H. Zhu, M. Zhang, J. Van der Spiegel, T. Lucas, "Somatosensory Encoding with Cuneate Nucleus Microstimulation: Detection of Artificial Stimuli", International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 2016.
[C7] J. Van der Spiegel, M. Zhang, X. Liu, "System-on-a-chip Brain-Machine-Interface design-a review and perspective," IEEE International Conference on Solid-State and Integrated Circuit Technology (ICSICT), Oct. 2016.
[C6] X. Liu, M. Zhang, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "A 12-Channel Bidirectional Neural Interface Chip with Integrated Channel-level Feature Extraction and PID Controller", IEEE Biomedical Circuits and Systems Conference (BioCAS), Oct. 2015.
[C5] X. Liu, B. Subei, M. Zhang, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "The PennBMBI: A general purpose wireless Brain-Machine-Brain Interface system for unrestrained animals," Circuits and Systems, 2014 IEEE International Symposium on (ISCAS), Jun. 2014.
[C4] W. Chen, X. Liu, B. Litt, "Logistic-weighted regression improves decoding of finger flexion from electrocorticographic signals", International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), Aug. 2014.
[C3] X. Liu, M. Zhang, H. Sun, A. G. Richardson, T. H. Lucas, and J. Van der Spiegel, "Design of a Net-Zero Charge Neural Stimulator with Feedback Control," 2014 IEEE Biomedical Circuits and Systems Conference (BioCAS), Oct. 2014.
[C2] X. Liu, M. Zhang, and J. Van der Spiegel, "A low power multi-mode CMOS image sensor with integrated on-chip motion detection," Circuits and Systems (ISCAS), 2013 IEEE International Symposium on, pp. 2416-2419, May 19-23, 2013.
[C1] J. Gong, W. Liu, X. Liu, and Tianxiang Cui, "A simulation-based performance comparison between multi-model assembly lines and assembly cells in a just-in-time environment," Chinese Control and Decision Conference, May 26-28, 2010.