Performance Characterization of Frequency-Selective Wireless Power Transfer Toward Scalable Untethered Magnetic Actuation

Jul 16, 2026

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Frequency-selective wireless power transfer enables independent actuation and control of multiple untethered robots in a shared workspace, yet the scaling limits within a given RF bandwidth remain unquantified. The study derives the relationship between resonator quality factor (Q-factor) and the maximum number of individually addressable LC resonant energy harvesters, then converts selectively harvested energy into mechanical motion. Theory and experiments show scalability depends primarily on Q-factor, supported by design equations and actuator demonstrations without cross-triggering.

LanguageEnglish

CategoryResearch & Report

FormatPDF

Pages8

Reading Time20 min

Introduction

Selective actuation in shared magnetic workspaces

Wireless power transfer approaches for robotic actuation

Motivation and research gap

Approach and contributions

Modeling Q-factor vs. addressable resonators

Frequency band selection (100 kHz to 1 MHz)

Experimental validation and performance characterization

Performance Characterization of Frequency-Selective Wireless Power Transfer Toward Scalable Untethered Magnetic Actuation Gabriel Cooper Department of Electrical and Computer Engineering Texas Tech University Lubbock, USA Xiaolong Liu∗ Department of Mechanical Engineering Texas Tech University Lubbock, USA arXiv :2604 . 11645v2 [ ee ss . SY] 11 Jul 2026 Abstract—Frequency-selective wireless power transfer provides a feasible route to enable independent actuation and control of multiple untethered robots in a common workspace; however, the scalability remains unquantified, particularly the maximum number of resonators that can be reliably addressed within a given frequency bandwidth. To address this, we formulate the relationship between resonator quality factor (Q-factor) and the number of individually addressable inductor-capacitor (LC) resonant energy harvesters within a fixed radio-frequency (RF) spectrum, and we convert selectively activated harvested energy into mechanical motion. We theoretically proved and experimentally demonstrated that scalability depends primarily on the Qfactor. For this proof-of-concept study, we define effective series resistance as a function of frequency allocating bandwidths to discrete actuators. We provide design equations for scaling untethered magnetic actuation with Q-factor optimization. Resonator networks spanning bandwidths from 100 kHz to 1 MHz were analyzed to quantify how increasing the number of resonators affects independent addressability. We validated the approach experimentally by fabricating three centimeter-scale untethered actuators that selectively trigger the motion of mechanical beams at 734 kHz, 785 kHz, and 855 kHz. We also characterized the generated mechanical force and the activation bandwidth of each actuator, confirming that no unintended cross-triggering occurred. Index Terms—frequency-selective power transfer, LC resonators, magnetic actuation, radio-frequency spectrum, scalability I. INTRODUCTION SELECTIVE actuation of untethered magnetic robots op erating in a shared workspace is a fundamental challenge because their actuation is inherently coupled through a common magnetic field source. Prior work has explored two main strategies for achieving selective actuation of magnetic robots, including the use of inhomogeneous magnetic fields to actuate robots at different spatial locations [1]–[5] and rotational stepout behavior in robots with different geometries or configurations [6], [7] . For example, global magnetic field dynamics exploit variations in magnetic material composition [6], robot geometry [7], [8], or robot placement in field gradients [1] to produce differentiated responses under a shared input field. Alternative approaches have achieved localized magnetic manipulation using two-dimensional (2-D) electromagnetic coil *Corresponding author: Xiaolong Liu (email: [xiaolong.liu@ttu.edu](xiaolong.liu@ttu.edu)). This work was supported in part by the National Science Foundation under Grant No. 2512394, in part by the Texas Tech HEF New Faculty Startup Fund, and in part by the Texas Tech TrUE and McNair Scholar Programs. arrays [2]–[4], which generate spatially controllable fields in 2-D spaces and enable independent control based on robot position. Rotational step-out frequency based actuation has also been investigated using rotating magnetic fields to drive robots with different geometries that experience different fluid drag, including helical swimmers [9], [10], and block-shaped robots [7] . These approaches provide important starting points, but they remain difficult to scale and generalize. Beyond approaches that rely on low frequency magnetic fields to achieve selective actuation of magnetic robots, wireless power transfer (WPT) techniques have been used to deliver RF magnetic energy to resonant circuits integrated into robotic devices, enabling actuation through mechanisms such as magnetic propulsion [11], heating shape me

FAQs

What problem does the paper address regarding frequency-selective wireless power transfer?

The work targets the lack of quantified limits on how many untethered robots can be individually addressed within a fixed RF frequency bandwidth while using frequency-selective wireless power transfer.

How does the paper link resonator performance to scalability?

It formulates and validates the relationship between resonator quality factor (Q-factor) and the maximum number of individually addressable LC resonant energy harvesters in a shared spectrum.

What experimental results were used to validate the approach?

The paper fabricated three centimeter-scale untethered actuators that selectively trigger mechanical beam motion at 734 kHz, 785 kHz, and 855 kHz, and it characterized force and activation bandwidth while confirming no unintended cross-triggering.

Jul 16, 2026

Upload by Himbo