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Device Technologies and Biomedical Robotics

Device Technologies and Biomedical Robotics - Poster Session D

Poster I12 - Novel Wearable Disposable Electrotherapy System Design

Friday, October 25, 2024
3:30 PM - 4:30 PM EST
Location: Exhibit Hall E, F & G

Introduction:  Wearable Disposable Electrotherapy is the first electrotherapy platform that provides auto-initiated (upon application to the skin) controlled electrical stimulation in a single-use, disposable, low-cost, conformable bandage form factor. Enabling these features is an integrated printed design, absent of any electronics (no circuit components), with power source, self-limiting mechanism, and interface elements made from environmentally benign common materials assembled by scalable additive manufacturing. The novel design of the Wearable Disposable Electrotherapy platform addresses interdependent constraints spanning automatically initiated and controlled dosing, power density, packaging, and scalable manufacturing with only common, environmentally benign, and nonhazardous materials. The device design supports broad application-specific flexibility (dose, placement). The battery pack discharge is initiated and governed by interaction, through the interface, with the target physiological load. Application-specific therapeutic dose is thus controlled by the device shape and battery pack design. This work presents a comprehensive workflow and steps of simulation and validation of application-specific Wearable Electrotherapy Devices.

Materials and

Methods:  The central innovation of this platform is avoidance of conventional electronics. The platform’s 3D architecture is manufactured entirely using additive/subtractive fabrication with common/benign materials including active materials based on alkaline Zn/MnO2 electrochemistry. Packing, power (maximum current, capacity), shape, and conformability design requirements are addressed in a novel iterative design workflow. The therapeutic dose is controlled through a printed structure using modular battery cells with interconnects.

A novel design process, governed by application-specific design inputs, separately: 1) characterizes interface-biological impedance loads across subjects; and 2) develops self-regulated battery cells, which are sized into battery packs. Then, the discharge of a designed battery pack through the interface/biological loads is simulated - supporting iterative battery/pack optimization, to ensure reliable output control across subjects.
Interfaces are tested for electrochemical capacity on a phantom, and the design refined accordingly, leading to characterization of load impedance.
Battery cell design is an iterative process involving architecture, anode/cathode inks, current collectors, separator membrane, and electrolyte. Battery cells with different designs and sizes undergo a range of verifications (e.g. galvanostatic discharge, shelf life, EIS) (Fig. 1). An iterative process to match the battery pack design with requirements of load, yield application-specific battery pack configuration, developed in parallel with sealing techniques, venting system, comfortability design, all under rigorous limits on acceptable manufacturing methods (scalable, economical, and environmentally benign). Final prototypes are tested against design inputs in human trials to validate each application of disposable Wearable Disposable Electrotherapy.

Results, Conclusions, and Discussions: For an exemplary device the input (the target dose) for design procedure is defined as 3 ± 1 mA average DC current over 20 min with a pair of hydrogel electrodes cut to size 25.2 cm2 (45 mm x 56 mm) as an interface. The 3D battery pack structure, cell shape, active materials, and mass inventory provide the requisite voltage and dose control.
The printing substrate that serves as the pouch for the battery pack is a flexible polyethylene terephthalate (PET) film. Screen printing and stencil printing are used for formation of each component. A stack of metallic ink, carbon-based ink and dielectric, each printed using screen printing forms interconnections, current collectors, through-holes and stimulation electrodes. Each design process is followed by tests to ensure reliable device operation. Next the batteries are printed by depositing designed cathode and anode inks, followed by placement of sealant and a separator membrane made from surfactant-coated microporous polypropylene film that prevents electrical shorts while providing ionic conduction between anode and cathode. The device is sealed with a specialized adhesive, and integrated vent channels to manage hydrogen gas buildup during shelf life. After sealing, a battery electrolyte is added to form a fully energized battery pack. Stimulation electrodes are covered by an ion-conductive hydrogel reinforced with non-woven felt as an interface to biological load.

We show that the creation of Wearable Disposable Electrotherapy involved development of a novel design workflow, which results in a self-limited dose control, novel battery cell technology, and battery pack architecture adapted to scalable manufacturing processes. These system design processes yield application-specific battery pack configurations, developed in parallel with sealing techniques, venting system, comfortability design, all under rigorous limits on acceptable manufacturing methods. For an exemplary device and three electrotherapy applications, the performance of each design element is verified, and efficacy is validated in human trials.

Acknowledgements (Optional):