PhD Thesis Defense: Md Saifur Rahman

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Meeting ID: 958 3252 4032
Passcode: 806033

"Designing flexible electronics integrating liquid metals and liquid-metal-derived surface oxides"

Abstract

The pursuit of advanced, flexible, and wearable electronics necessitates innovative approaches to overcome the limitations of traditional materials and methods. This thesis explores a unified approach to liquid metal-based electronics across three domains: stretchable radio frequency sensors, efficient soft magnetic devices, and transparent oxide electronics for biointerfaces. Gallium-based room-temperature liquid metals offer unique advantages in deformability, conductivity, and surface reactivity, enabling innovations across all three areas.

First, we introduced a method for high-frequency AC-enhanced resistive sensing using deformable liquid metals to improve low-power detection in wearable electronics. By modulating electromagnetic effects, such as current crowding due to the skin effect, this method can quantitatively distinguish mechanical deformation modes. Additionally, this method can produce an energy-efficient yet high SNR, producing a stretchable mechanical sensor that has been shown in sensing gloves and in a breathing monitoring setup. Second, we present a low-loss, high-Q inductor architecture using 3D-woven liquid metal 'litz' wires. By mitigating proximity and skin effects, this design enhances RF coil efficiency and offers a pathway toward soft wireless power interfaces. Finally, we demonstrated an automated method to extract and deposit a transparent, ultrathin yet highly conductive liquid metal oxide skin from the In-Tin liquid metal alloy onto flexible substrates. Non-invasive dry bioelectrodes made of transparent oxide films provide superior strain compliance, adhesion, and abrasion resistance compared to standard alternatives. The conductivity and transparency of 2D ITO were used for synchronous, multimodal measurements via electrocardiography (ECG) and pulse plethysmography (PPG). By creating a flexible electronic wearable system, we utilized these bendable and transparent oxide films as bioelectrode material in a multimodal biosignal acquisition setup.

Thesis Committee

• William J. Scheideler (chair)
• Jifeng Liu
• Hui Fang
• TJ Wallin (MIT)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu.