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    Device Technologies and Biomedical Robotics

    Motor Characterization of a Wearable Device to Treat Upper Extremity Lymphedema

    (K-402) Motor Characterization of a Wearable Device to Treat Upper Extremity Lymphedema

    Saturday, October 14, 2023
    9:30 AM – 10:30 AM PDT
    Location: Exhibit Hall - Row K - Poster # 402
    Introduction:: 3 to 5 million Americans and 140 to 200 million people worldwide are affected by lymphedema [1,2]. The buildup of protein-rich lymphatic fluid in the interstitial tissue spaces causes painful swelling. This chronic, progressive condition is treatable, but not curable, leaving patients with debilitating symptoms that can significantly impair their quality of life [3]. Lymphedema is a common result of radiation, chemotherapy, and surgical treatment of cancer. We have created a wearable device to manage upper-extremity lymphedema. Other devices on the market use pneumatic bladders that require an air compressor, restricting patient mobility. Our device uses eccentric rotating mass vibration motors to create patterns of massage that mimic manual lymphatic drainage massage - the standard therapy. The purpose of the wearable device is to provide more freedom and flexibility for the user by allowing for mobile use of the device. This study characterizes the vibration acceleration and frequency produced by motors with and without custom housing pods. Additionally, we analyzed the effect of a velcro strap to secure the pods. Further data was collected to understand how the accelerations and frequencies change when the motors are located at different spacings from the accelerometer, in order to determine how the vibration spreads. The goal of this study is to optimize the device performance for future clinical studies.

    Materials and Methods:: A cylindrical tissue phantom was made using a 2:1 ratio of Dragon Skin (10 Medium, Smooth-on) and mineral oil (Baby Oil, Johnson’s) [4] to simulate the upper arm. The diameter of the phantom is 10 cm, with a height of 27.5 cm [5]. An accelerometer (MetaMotionC, MBientLab) was inserted into the center of the cylinder to capture acceleration data in the x, y, and z directions. A rubberband was wrapped around the accelerometer for placement and removal. A sleeve was created using the same material as the wearable device (90% Polyester, 10% Spandex) and placed onto the model with pod spacings at four diagonal distances (75 mm above, 50 mm in parallel with, 75 mm below, and 100 mm below the accelerometer) as seen in Figure 1. The vibration motor (NFP-E1015, NFP Motor) was placed into a pod and put into the sleeve, which was then wired to the power supply to set a particular voltage. The sleeve and motor were secured to the phantom using a velcro strap mimicking the full device. The phantom was then placed on a styrofoam block to minimize reflecting vibrations from the table. The motor was run at voltages of 1.2, 1.8, 2.4, and 3.0 V. This correlates to duty cycles of 102, 153, 204, and 255, respectively. The accelerations and frequencies were measured at all distances using 4 different motors. This was repeated using a motor-only sleeve without the pod housing, made of the same sleeve material.

    Results, Conclusions, and Discussions:: As seen in Figure 2A, the no-pod setup followed a concave quadratic pattern, and the accelerations generally corresponded with the voltage supplied. Acceleration correlates with the distance between the accelerometer and the motor.  However, there are some outliers that are difficult to explain without further testing. In Figure 2B, running the motors in pods at 2.4V showed the most variability compared to other voltages, as there were instances where it produced higher and lower accelerations than expected. However, when the motors were supplied with 1.2V they were significantly more predictable across all distances with and without a pod. This indicates that the motors were more variable at higher voltages using our setup including the velcro sleeve, and this effect on the wearable device will be determined in the future.

    This data was taken from the same distance away from the accelerometer of -75 mm. Specifically, the average acceleration was found to be higher in all voltage cases when the motor is encased in a pod, as seen in Figure 3A. For frequency, the pod had higher averages in all voltages excluding 1.2V, as shown in Figure 3B. Additionally, the motor encased in the pod demonstrated a positive correlation with voltage. From this information, it can be concluded that the pod is beneficial in producing higher accelerations and frequencies at most duty cycles than without.


    It is interesting to note that the accelerations were significantly higher with a velcro strap than without (data not shown). This indicates that the use of the velcro strap in the current wearable is useful in increasing the accelerations produced by the motor at all voltages. Additionally, for all voltages excluding 1.2V, the motor without a velcro strap had a higher average frequency. This shows that with an increase in acceleration, the velcro strap also causes a decrease in average frequency.




    Future goals would consider various pod types and the effect of different motor configurations, such as activating multiple motors simultaneously. This motor characterization will aid in the future development of the wearable device.




    Acknowledgements (Optional): : We would like to thank Leah Thomas, Laura Wenger, Evgeniya Molotkova, and Gino DiMatteo. Funding was awarded through the Carilion Innovation Proof-of-Concept Program.

    References (Optional): :

    [1]Foldi, Michael. Foldi's textbook of lymphology for physicians and lymphedema therapists.  Mosby Elsevier, Missouri (2006).


    [2]Cemal, Yeliz, Pusic, Andrea, and Mehrara, Babak. “Preventative measures for lymphedema: Separating fact from fiction.” Journal of the American College of Surgeons Vol. 213, No. 4 (2011):  pp. 543–551. DOI 10.1016/j.jamcollsurg.2011.07.001 


    [3]E. Poage, M. Singer, J. Armer, M. Poundall, and M. J. Shellabarger, “Demystifying lymphedema: Development of the lymphedema putting evidence into Practice® Card,” Clinical Journal of Oncology Nursing, vol. 12, no. 6, pp. 951–964, 2008. 


    [4]Wang, Yancheng, Tai, Bruce, Yu, Hongwei, and Shih, Albert. “Silicone-based tissue-mimicking phantom for needle insertion simulation.” Journal of Medical Devices Vol. 8 No. 2 (2014)


    [5]“Vital and Health Statistics Analytical and Epidemiological Studies.” Available: https://www.cdc.gov/nchs/data/series/sr_03/sr03-046-508.pdf