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Wenchi Liu

Publications and source records attributed to Wenchi Liu.

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Towards Knitted Textile Electromechanical Systems

E-textiles and wearable sensing technologies enable flexible, customizable interfaces for human-computer interaction, with capacitive sensing offering precise touch and pressure detection. While machine knitting provides scalable, mechanically tunable structures ideal for such sensors, few studies develop or characterize insulated conductive yarns engineered for knitting's complex structural geometry and high flexure strain. In this work, we present a yarn dip-coating process, driven by an adjusted dip-coating fluid dynamics model, that enables scalable, machine knittable fabrication of capacitive tactile pressure sensing arrays. We establish optimal dip-coating parameters and concentrations of thermoplastic polyurethane (TPU) dissolved in dimethylformamide (DMF) to create knitting-optimized coatings (~630 um thickness). These fabricated yarns are shown to maintain electromechanical characteristics with minimal deviation after knitting and washing, thus allowing the creation of knitted pressure sensors through multi-layered structures. This process demonstrates that machine knitting with insulated yarns is a viable and reliable manufacturing approach to integrate sensing functionality into wearable textiles.

cs.HC

Designing heterostructures to control oxygen stoichiometry in helimagnetic perovskite strontium ferrite

A large challenge in determining the physics of helimagnetic SrFeO3 is in stabilizing the stoichiometric chemical phase over long enough time scales to conduct extensive measurements. Degradation in SrFeO3 manifests mainly as a crossover from metallic to insulating behavior. Using a combination of electronic transport and density functional theory, we show that this degradation is dominated by oxygen loss, possibly on the order of one percent. We further demonstrate that high quality SrFeO3 thin films can be stabilized long-term by combining a nanoscale band insulator capping layer with an ex situ ozone anneal. We show that this produces a nearly-pristine cation sublattice and preserves metallicity for at least several weeks. These results establish a reliable pathway for producing chemically stable SrFeO3 thin films, enabling reproducible studies of its unusual helimagnetism.

cond-mat.mtrl-sci