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Creators/Authors contains: "Hajiaghajani, Amirhossein"

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  1. Free, publicly-accessible full text available August 19, 2025
  2. Abstract

    The human body exhibits complex, spatially distributed chemo-electro-mechanical processes that must be properly captured for emerging applications in virtual/augmented reality, precision health, activity monitoring, bionics, and more. A key factor in enabling such applications involves the seamless integration of multipurpose wearable sensors across the human body in different environments, spanning from indoor settings to outdoor landscapes. Here, we report a versatile epidermal body area network ecosystem that enables wireless power and data transmission to and from battery-free wearable sensors with continuous functionality from dry to underwater settings. This is achieved through an artificial near field propagation across the chain of biocompatible, magneto-inductive metamaterials in the form of stretchable waterborne skin patches—these are fully compatible with pre-existing consumer electronics. Our approach offers uninterrupted, self-powered communication for human status monitoring in harsh environments where traditional wireless solutions (such as Bluetooth, Wi-Fi or cellular) are unable to communicate reliably.

     
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  3. 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.

     
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  4. 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.

     
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  5. Abstract

    Wearable wireless passive sensors are powerful potential building blocks of modern body area networks. However, these sensors are often hampered by numerous issues including restrictive read‐out distances due to near‐field coupling, fundamental tradeoffs in size/spectral performance, and unreliable sensor tracking during activity. Here, to overcome such issues implementing wearable sensing systems exhibiting coupled magnetic resonances are demonstrated. This approach is utilized to augment wireless telemetry from fully wearable, passive (zero electronics) resonator chains. Secondary receiver coils are integrated into fabric or skin to facilitate augmented read‐out from epidermal sweat, moisture, or pressure sensors—herein exhibiting enhanced read‐out range, relaxed constraints in sensor size (sensor spectral response becomes untethered from size) and reader‐sensor orientation. Unlike existing schemes, this readout method enables decoupled co‐readout of the sensor's distance and status, employed here for co‐measurement with human respiration. This type of decoupled readout can help compensate for movements that are so common in wearable monitoring. Simple to implement and requiring no microelectronics, this scheme streamlines into existing, body‐worn passive wireless telemetric systems with minimal modification.

     
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  6. 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.

     
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