Power-on-Touch: Powering Actuators, Sensors, and Devices during Interaction

Research Background and Problem Statement

• Issues and Challenges: With the increasing number of interactive devices in smart environments, power supply has become a major challenge in ubiquitous computing scenarios. Currently, most devices rely on battery power, but batteries require frequent replacement or recharging, which is impractical in scenarios involving a large number of devices. Furthermore, existing battery-powered or intermittently powered devices cannot meet the power demands of high-energy components such as actuators (e.g., vibration motors, ultrasonic generators).
• Significance: If a new method can provide instant power, it would not only reduce the burden of battery maintenance but also enhance the adoption of high-power interactive devices (e.g., haptic devices and actuators), thereby driving technological advancements in the field of ubiquitous computing.
• Research Motivation: To improve the accessibility and diversity of power for devices, surpassing traditional low-power sensing devices, and to explore solutions for power demands that include high-power actuators.

Proposed Solution

• Method or Solution:
  • A method called Power-on-Touch is proposed, which powers devices during interaction using a wireless power transmission module worn by the user, eliminating the need for batteries.
  • It consists of two main components: a transmitter module worn by the user (with a coil and battery) and a receiver tag embedded in the device to enable inductive power transfer.
• Innovations:
  • Enables on-demand power supply to devices during interaction, surpassing previous technologies that only supported low-power devices.
  • Utilizes inductive power transfer without requiring precise circuit alignment, enhancing robustness for various interaction touch forms (e.g., gripping, touching, and hovering).
  • Compatible with various designs for inductive power transfer, including flexible coils and spherical coils, to support more efficient power transmission.
• Implementation Steps and Key Technologies:
  1. Inductive Coupling Circuit Design:
     • Optimized power transfer efficiency by tuning the resonance frequency of the coil circuit (resonant inductive coupling technology).
  2. Coil Optimization Design:
     • Developed large coils (suitable for the back of the hand), small coils (suitable for fingernails), and spherical coils (supporting omnidirectional power transfer).
     • Introduced magnetic backing to optimize the transmission efficiency of small coils.
  3. Transmitter and Receiver Module Development:
     • The transmitter module includes a battery, voltage booster, BLE microcontroller unit, and can detect the presence of the receiver coil via test pulses.
     • The receiver module coordinates the power needs of high-power devices through rectification, supercapacitor energy storage, and a BLE microcontroller.
  4. Performance Tuning and Safety Testing:
     • Enhanced transmission efficiency through impedance analysis; tested system performance under varying distances, angles, and loads.
     • Evaluated human electromagnetic absorption rates and thermal effects to ensure safety.

Research Outcomes

• Key Results:
  • Successfully developed a system that powers various types of devices through user interaction, supporting multiple wireless power application scenarios, including sensors (μW level) and actuators (W level).
  • Provided detailed technical evaluations, including coil quality factor (Q-factor) analysis, power transfer efficiency measurements, and 3D efficiency mapping. Optimized numerous variables affecting coil design.
• Advantages:
  • Devices no longer require built-in batteries, significantly reducing maintenance costs.
  • Robust support for various touch postures, such as misaligned touches and hovering, while still providing sufficient power.
  • The system is compatible with high-power devices, expanding the possibilities of interactive technologies.
• Experiments and Evaluations:
  • Tested three real-world devices (a remote control, a microphone, and a door handle with an electric lock), demonstrating the system's ability to charge from zero voltage to operational state and its power supply performance under different touch forms.
  • Measurements verified the system's power reserve capabilities, such as the ability of supercapacitors to charge quickly to meet high-power peak demands.
  • Safety tests confirmed compliance with IEC 60601 standards for human electromagnetic radiation absorption rates, with controllable thermal effects.
• Limitations and Future Directions:
  • Limitations:
    • Inductive power transfer efficiency is lower compared to wired connections.
    • Retrofitting existing devices requires structural and form adjustments.
    • Conditions are limited to scenarios where the device is in close proximity to the user's coil.
  • Future Directions:
    • Improve dynamic impedance matching and frequency tuning to further enhance transmission efficiency.
    • Explore wearable forms that align with societal acceptance (e.g., integration into fashion accessories or textiles).
    • Expand to larger-scale multi-user simultaneous interaction scenarios.

By open-sourcing the detailed implementation methods, this paper provides the academic community with a novel and replicable solution, driving innovation in the fields of ubiquitous computing and power supply.