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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session E

Poster J14 - WaveSoothe: Compression Therapy via Silicone-Based Soft Actuators

Saturday, October 26, 2024
10:00 AM – 11:00 AM EST
Location: Exhibit Hall E, F & G

Introduction:  Wavesoothe is a noninvasive compressive therapy device targeting chronic vein insufficiency (CVI) patients. CVI is a common malfunctioning of vein valves in the legs. Chronics venous diseases (CVD) impact 25 million adults in the United States (estimation from 2014), with 6 million suffering from advanced conditions. Current CVI treatments include compression treatments, physical therapy, medications, radiofrequency ablation, and vein ligation surgery. Access to these treatments (e.g., precious physical therapy) is often limited. This study developed a programmable compressive therapeutic device (Wavesoothe) that combines soft material actuators enacted by oscillating pneumatic pressure to improve circulation and minimize complications. The abstract details the platform (actuators and control units), do-it-yourself (DIY) testing tools, and primary results. Wavesooth performance against clinically established parameters suggested that some requirements (e.g., similar contact pressures as standard compression devices at safe, consistent operating frequencies) could be achieved. Ongoing advances in soft robots and soft actuators could provide alternative therapeutics to many patients. Wavesoothe represents a successful prototype for CVI treatment with this approach.

Materials and

Methods:  The primary Wavesoothe system combines (a) a pneumatically controlled soft actuator, (b) a DIY electronics, and (c) a sleeve to attach the actuators to a patient's leg. Additional tools (pressure and force DAQ systems) had to be developed (Figure 1). 3D-printed PLA molds were developed to cast the soft actuators via EcoFlex 30 silicone. Molds were partially filled with silicone and thermally cured. Next, to enable deflections, a vinyl sheet (2mm x 160mm x 100mm) was placed inside the mold, which was fully filled with silicone (Figure 2). A mechano-electronic hub was developed to control the Wavesooth system. These included DIY electronics, mechanics (solenoids and a diaphragm pump), an Arduino UNO microcontroller, and 3D-printed housing parts. These components controlled the sequential flow of air into the soft actuators. Briefly, since solenoids require more power than the microcontrollers could provide, a circuit (and corresponding PCB boars) was designed to amplify the small microcontroller signals. Additionally, a circuit was designed to simplify the power requirements to power both the solenoids and the pump from a single 12V AC Adapter (Figure 3). The pressure of the soft actuator was measured, as well as both internal and contact pressure. For internal pressure, an analog differential pressure sensor was used for each channel of the soft actuator (Figure 3). A force-sensitive resistor (Figure 3) was used to test pressure when applied to a model calf (Figure 4). Both pressure sensors created a device powered by Arduino Nano ESP-32 to record samples at 200Hz.

Results, Conclusions, and Discussions: Wavesooth was successfully integrated. Internal pressure readings from the system suggested that the maximum pneumatic pressure of 2-4kPa could be reached (Figure 4). Through Arduino, three timers were set to run at 1Hz with a phase shift of 120°. The internal pressure graphs (Figure 4) indicate that the device oscillated at 1Hz, and each channel shifted phase. The pressure exerted by the soft actuator had to be indirectly measured. An FSR’s resistance changes inversely to pressure. Resistance was graphed with respect to time, and the average through resistance was used to find the maximum contact pressure (Figure 4). To convert resistance to pressure, the known weights were used to calibrate the device and the sensor’s datasheet. Given that an FSR is accurate within 20% of the actual force, it was estimated that the pressure exerted by the soft actuator onto a flat surface is 4.5kPa +/- 1kPa. The results suggest that WaveSoothe can provide similar contact pressures as standard compression devices at safe, consistent operating frequencies despite using soft material for oscillating actuation (Figure 4). The actuators could be modified in future iterations to enable more pressure and faster actuation. Replacing hard components with embedded control (logic made out of soft components) is highly desirable.

Acknowledgements (Optional):