Stanford Advisors

All Publications

  • Real-Time Gait Phase Detection on Wearable Devices for Real-World Free-Living Gait. IEEE journal of biomedical and health informatics Wu, J., Becsek, B., Schaer, A., Maurenbrecher, H., Chatzipirpiridis, G., Ergeneman, O., Pane, S., Torun, H., Nelson, B. J. 2022; PP


    Detecting gait phases with wearables unobtrusively and reliably in real-time is important for clinical gait rehabilitation and early diagnosis of neurological diseases. Due to hardware limitations of microcontrollers in wearable devices (e.g., memory and computation power), reliable real-time gait phase detection on the microcontrollers remains a challenge, especially for long-term real-world free-living gait. In this work, a novel algorithm based on a reduced support vector machine (RSVM) and a finite state machine (FSM) is developed to address this. The RSVM is developed by exploiting the cascaded K-means clustering to reduce the model size and computation time of a standard SVM by 88% and a factor of 36, with only minor degradation in gait phase prediction accuracy of around 4%. For each gait phase prediction from the RSVM, the FSM is designed to validate the prediction and correct misclassifications. The developed algorithm is implemented on a microcontroller of a wearable device and its real-time (on the fly) classification performance is evaluated by twenty healthy subjects walking along a predefined real-world route with uncontrolled free-living gait. It shows a promising real-time performance with an accuracy of 91.51%, a sensitivity of 91.70%, and a specificity of 95.77%. The algorithm also demonstrates its robustness with varying walking conditions.

    View details for DOI 10.1109/JBHI.2022.3228329

    View details for PubMedID 37015703

  • Human gait-labeling uncertainty and a hybrid model for gait segmentation FRONTIERS IN NEUROSCIENCE Wu, J., Maurenbrecher, H., Schaer, A., Becsek, B., Easthope, C., Chatzipirpiridis, G., Ergeneman, O., Pane, S., Nelson, B. J. 2022; 16: 976594


    Motion capture systems are widely accepted as ground-truth for gait analysis and are used for the validation of other gait analysis systems. To date, their reliability and limitations in manual labeling of gait events have not been studied.Evaluate manual labeling uncertainty and introduce a hybrid stride detection and gait-event estimation model for autonomous, long-term, and remote monitoring.Estimate inter-labeler inconsistencies by computing the limits-of-agreement. Develop a hybrid model based on dynamic time warping and convolutional neural network to identify valid strides and eliminate non-stride data in inertial (walking) data collected by a wearable device. Finally, detect gait events within a valid stride region.The limits of inter-labeler agreement for key gait events heel off, toe off, heel strike, and flat foot are 72, 16, 24, and 80 ms, respectively; The hybrid model's classification accuracy for stride and non-stride are 95.16 and 84.48%, respectively; The mean absolute error for detected heel off, toe off, heel strike, and flat foot are 24, 5, 9, and 13 ms, respectively, when compared to the average human labels.The results show the inherent labeling uncertainty and the limits of human gait labeling of motion capture data; The proposed hybrid-model's performance is comparable to that of human labelers, and it is a valid model to reliably detect strides and estimate the gait events in human gait data.This work establishes the foundation for fully automated human gait analysis systems with performances comparable to human-labelers.

    View details for DOI 10.3389/fnins.2022.976594

    View details for Web of Science ID 000901945700001

    View details for PubMedID 36570841

    View details for PubMedCentralID PMC9773262

  • Motion Analysis and Real-Time Trajectory Prediction of Magnetically Steerable Catalytic Janus Micromotors ADVANCED INTELLIGENT SYSTEMS Wu, J., Folio, D., Zhu, J., Jang, B., Chen, X., Feng, J., Gambardella, P., Sort, J., Puigmarti-Luis, J., Ergeneman, O., Ferreira, A., Pane, S. 2022; 4 (11)
  • An Intelligent In-Shoe System for Gait Monitoring and Analysis with Optimized Sampling and Real-Time Visualization Capabilities SENSORS Wu, J., Kuruvithadam, K., Schaer, A., Stoneham, R., Chatzipirpiridis, G., Easthope, C., Barry, G., Martin, J., Pane, S., Nelson, B. J., Ergeneman, O., Torun, H. 2021; 21 (8)


    The deterioration of gait can be used as a biomarker for ageing and neurological diseases. Continuous gait monitoring and analysis are essential for early deficit detection and personalized rehabilitation. The use of mobile and wearable inertial sensor systems for gait monitoring and analysis have been well explored with promising results in the literature. However, most of these studies focus on technologies for the assessment of gait characteristics, few of them have considered the data acquisition bandwidth of the sensing system. Inadequate sampling frequency will sacrifice signal fidelity, thus leading to an inaccurate estimation especially for spatial gait parameters. In this work, we developed an inertial sensor based in-shoe gait analysis system for real-time gait monitoring and investigated the optimal sampling frequency to capture all the information on walking patterns. An exploratory validation study was performed using an optical motion capture system on four healthy adult subjects, where each person underwent five walking sessions, giving a total of 20 sessions. Percentage mean absolute errors (MAE%) obtained in stride time, stride length, stride velocity, and cadence while walking were 1.19%, 1.68%, 2.08%, and 1.23%, respectively. In addition, an eigenanalysis based graphical descriptor from raw gait cycle signals was proposed as a new gait metric that can be quantified by principal component analysis to differentiate gait patterns, which has great potential to be used as a powerful analytical tool for gait disorder diagnostics.

    View details for DOI 10.3390/s21082869

    View details for Web of Science ID 000644797100001

    View details for PubMedID 33921846

    View details for PubMedCentralID PMC8074136

  • Helical Klinotactic Locomotion of Two-Link Nanoswimmers with Dual-Function Drug-Loaded Soft Polysaccharide Hinges ADVANCED SCIENCE Wu, J., Jang, B., Harduf, Y., Chapnik, Z., Avci, O., Chen, X., Puigmarti-Luis, J., Ergeneman, O., Nelson, B. J., Or, Y., Pane, S. 2021; 8 (8): 2004458


    Inspired by the movement of bacteria and other microorganisms, researchers have developed artificial helical micro- and nanorobots that can perform corkscrew locomotion or helical path swimming under external energy actuation. In this paper, for the first time the locomotion of nonhelical multifunctional nanorobots that can swim in helical klinotactic trajectories, similarly to rod-shaped bacteria, under rotating magnetic fields is investigated. These nanorobots consist of a rigid ferromagnetic nickel head connected to a rhodium tail by a flexible hydrogel-based hollow hinge composed of chemically responsive chitosan and alginate multilayers. This design allows nanoswimmers switching between different dynamic behaviors-from in-plane tumbling to helical klinotactic swimming-by varying the rotating magnetic field frequency and strength. It also adds a rich spectrum of swimming capabilities that can be adjusted by varying the type of applied magnetic fields and/or frequencies. A theoretical model is developed to analyze the propulsion mechanisms and predict the swimming behavior at distinct rotating magnetic frequencies. The model shows good agreement with the experimental results. Additionally, the biomedical capabilities of the nanoswimmers as drug delivery platforms are demonstrated. Unlike previous designs constitute metallic segments, the proposed nanoswimmers can encapsulate drugs into their hollow hinge and successfully release them to cells.

    View details for DOI 10.1002/advs.202004458

    View details for Web of Science ID 000617877300001

    View details for PubMedID 33898199

    View details for PubMedCentralID PMC8061375

  • Peroxymonosulfate activation for efficient sulfamethoxazole degradation by Fe3O4/beta-FeOOH nanocomposites: Coexistence of radical and non-radical reactions CHEMICAL ENGINEERING JOURNAL Li, C., Wu, J., Peng, W., Fang, Z., Liu, J. 2019; 356: 904-914
  • Optimal Operation and Control of Fluidized Bed Membrane Reactors for Steam Methane Reforming Marquez-Ruiz, A., Wu, J., Ozkan, L., Gallucci, F., Annaland, M., Kiss, A. A., Zondervan, E., Lakerveld, R., Ozkan, L. ELSEVIER SCIENCE BV. 2019: 1231-1236