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Abstract Ion consumption plays key roles in maintaining bodily homeostasis and health. Here passive wireless, multimineral comonitoring arrays are studied that may potentially be utilized for emerging applications in precision nutrition. RF biosensors targeting select minerals (calcium or magnesium demonstrated herein) are built from integrating ion‐selective membranes within a broadside‐coupled split ring resonator architecture. RF sensors are typically monitored one at a time and such platforms often are incapable of comeasuring multiple confounding components. To address this challenge, this sensor arrays are further directly integrated alongside a conformal, custom readout coil that optimizes multi‐RF sensor readout. Such optimized networks exhibit enhanced signal clarity, further facilitating coextraction of multiple ion components. A simple method of extracting multimineral concentrations from food even despite the imperfect selectivity of divalent ion‐selective membranes is introduced. This passive wireless, zero‐electronic ion‐monitoring platform integrates seamlessly on foodware or packaging, possessing many applications in food measurement. 

Abstract Current joint angle monitoring techniques—essential for evaluating biomechanical functions and rehabilitation outcomes—face significant challenges. These may include dependency on specific environmental lighting and clear line‐of‐sight, complex setup and calibration, or sensing modalities that may interfere with natural motion. Additionally, the durability of these methods is often compromised by mechanical failures due to repetitive motion. Here, textile (or skin‐borne) strongly coupled magnetic resonators that can be distributed cross‐body to form advanced joint monitoring networks is demonstrated. Flexible magneto‐inductive loops can be positioned adjacent to joints, continuously monitoring limb coordination without being directly subjected to large joint strains. Such a technique minimizes both impediments to joint motion and material fatigue. Networks are lastly utilized to monitor and identify limb activity during diverse user stretches and exercises. 

Abstract Passive and wireless Radio‐Frequency (RF) sensors are a unique, enabling modality for emerging applications in environmental sensing. These sensors exhibit several key features that may unlock new functionalities in complex environments: sensors are composed of zero electronic components, are wirelessly interrogated even in opaque media, and structures are often inherently biocompatible. Such capabilities make it unique in the realm of sensing architectures. Here, the broadside‐coupled, split‐ring resonator is studied as a compact and versatile model structure for RF sensing (of potentially mechanical and biochemical environments). A new analytical model is derived to assess resonator behavior—these yield a rapid, first‐order approximation of the resonator resonant frequency or sensitivity. Finally, experimental investigations into how sensors may be optimally designed, sized, and interrogated to enhance sensitivity or spectral intensity are performed. These studies encompass a wide variety of potential dimensional and dielectric modifications that may be relevant to emerging sensors. Last, hydrogel polymeric sensors are synthesized and studied to assess how practical sensors may deviate in response from expectations. Such investigations lay the groundwork for how such sensing architectures may be adapted to fit application needs. 

Abstract Nutrition measurement has broad applications in science, ranging from dietary assessment, to food monitoring, personalized health, and more. Despite its importance, there are currently no tools that offer continuous cotracking of nutrients direct from food. In this study, the multiscale engineering of silk biopolymer‐interlayer sensors is reported for comonitoring of nutrients. By manipulating various nano‐ to mesostructural properties of such biosensors, sensors are obtained with programmable sensitivity and selectivity to salts, sugars, and oils/fats. Notably, this approach requires no specialized nanomaterials or delicate biomolecules. Programmable biosensors are further formatted for wireless readout and characteristics of these passive, wireless nutrient monitors are studied in vitro. As a proof of concept, the discrimination and comonitoring of salt, sugar, and fat content direct from real, complex foods such as milk, meat, soup, and tea drinks are demonstrated. It is anticipated that such sensors can be utilized in emerging dietary tools for applications across food tracking and human health. In addition, such strategies are expected in structural engineering of sensors to be adaptable to existing or emerging selective or partially selective sensors.