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With the growing need for privacy and self-sovereign identity, traditional identity management relying on centralized data registries not only represents single points of failure but also lacks transparency and control over users’ identity information. With the built-in tamper-proofness and transparency, blockchain has been widely studied to accommodate the challenges in traditional identity management. Still, it usually comes with privacy concerns due to its public accessibility. Anonymous credentials take advantage of the recent progress in zero-knowledge proof, allowing the unlinkable presentation of only the necessary attributes for a service to guarantee anonymity. However, the existing anonymous credentials require a secondary issuer to verify and manage the anonymized credentials, which compromises the overall transparency and causes indirect management of the user’s identity. In this paper, we propose GrAC, a blockchain-based identity management system based on a novel identity graph, which allows users and identity providers to securely store and manage identity information on the blockchain without intermediate entities. GrAC also includes an anonymous authentication protocol suite based on zero-knowledge proof, allowing users to generate one-time anonymous credentials that selectively reveal minimal information to the service provider for authentication. The analysis and evaluations show that GrAC has a reasonable overhead and provides adequate anonymity protection while removing the need for intermediate issuers. 

Objective and Impact Statement . Real-time monitoring of the temperatures of regional tissue microenvironments can serve as the diagnostic basis for treating various health conditions and diseases. Introduction . Traditional thermal sensors allow measurements at surfaces or at near-surface regions of the skin or of certain body cavities. Evaluations at depth require implanted devices connected to external readout electronics via physical interfaces that lead to risks for infection and movement constraints for the patient. Also, surgical extraction procedures after a period of need can introduce additional risks and costs. Methods . Here, we report a wireless, bioresorbable class of temperature sensor that exploits multilayer photonic cavities, for continuous optical measurements of regional, deep-tissue microenvironments over a timeframe of interest followed by complete clearance via natural body processes. Results . The designs decouple the influence of detection angle from temperature on the reflection spectra, to enable high accuracy in sensing, as supported by in vitro experiments and optical simulations. Studies with devices implanted into subcutaneous tissues of both awake, freely moving and asleep animal models illustrate the applicability of this technology for in vivo measurements. Conclusion . The results demonstrate the use of bioresorbable materials in advanced photonic structures with unique capabilities in tracking of thermal signatures of tissue microenvironments, with potential relevance to human healthcare. 

Abstract Recently developed methods for transforming 2D patterns of thin‐film materials into 3D mesostructures create many interesting opportunities in microsystems design. A growing area of interest is in multifunctional thermal, electrical, chemical, and optical interfaces to biological tissues, particularly 3D multicellular, millimeter‐scale constructs, such as spheroids, assembloids, and organoids. Herein, examples of 3D mechanical interfaces are presented, in which thin ribbons of parylene‐C form the basis of transparent, highly compliant frameworks that can be reversibly opened and closed to capture, envelop, and mechanically restrain fragile 3D tissues in a gentle, nondestructive manner, for precise measurements of viscoelastic properties using techniques in nanoindentation. Finite element analysis serves as a design tool to guide selection of geometries and material parameters for shape‐matching 3D architectures tailored to organoids of interest. These computational approaches also quantitate all aspects of deformations during the processes of opening and closing the structures and of forces imparted by them onto the surfaces of enclosed soft tissues. Studies of cerebral organoids by nanoindentation show effective Young's moduli in the range from 1.5 to 2.5 kPa depending on the age of the organoid. This collection of results suggests broad utility of compliant 3D mesostructures in noninvasive mechanical measurements of millimeter‐scale, soft biological tissues.