Compact electronic systems that perform rapid, precise mechanical characterization of living biological tissues have important potential uses in monitoring and diagnosing various types of human-health disorders. Active devices that perform high-precision, real-time evaluations of deep tissue structures (millimeter-scale) in a precise, digital and non-invasive fashion could complement capabilities of recentlyreported approaches for sensing tissue biomechanics at super cial depths (typically micrometer-scale).This paper introduces a miniature electromagnetic platform that combines a vibratory actuator with a soft strain-sensing sheet for determining the Young's modulus of soft biological tissues, with speci c focus on skin. Experimental and computational studies establish the operational principles and performance attributes through evaluations of synthetic and biological materials, including human skin at various body locations across healthy subject volunteers. The results demonstrate dynamic monitoring of elastic modulus at characteristic depths between ~1 and ~8 mm, depending on the sensor designs.Arrays of such devices support capabilities in both depth pro ling and spatial mapping. Clinical studies on patients with skin disorders highlight potential for accurate targeting of lesions associated with psoriasis, as examples of practical medical utility.

Surface-enhanced Raman scattering (SERS) is recognized as one of the most sensitive spectroscopic tools for chemical and biological detections. Hotspots engineering has expedited promotion of SERS performance over the past few decades. Recently, molecular enrichment has proven to be another effective approach to improve the SERS performance. In this work, we propose a concept of “motile hotspots” to realize ultrasensitive SERS sensing by combining hotspots engineering and active molecular enrichment. High-density plasmonic nanostructure-supporting hotspots are assembled on the tubular outer wall of micromotors via nanoimprint and rolling origami techniques. The dense hotspots carried on these hierarchically structured micromotors (HSMs) can be magnet-powered to actively enrich molecules in fluid. The active enrichment manner of HSMs is revealed to be effective in accelerating the process of molecular adsorption. Consequently, SERS intensity increases significantly because of more molecules being adjacent to the hotspots after active molecular enrichment. This “motile hotspots” concept provides a synergistical approach in constructing a SERS platform with high performance. Moreover, the newly developed construction method of HSMs manifests the possibility of tailoring tubular length and diameter as well as surface patterns on the outer wall of HSMs, demonstrating good flexibility in constructing customized micromotors for various applications.

Three-dimensional microstructures fabricated by origami, including folding, rolling and buckling, gain great interests in mechanics, optics and electronics. We propose a general strategy on on-demand and spontaneous rolling origami for artificial microstructures aiming at massive and intelligent production. Deposited nanomembranes are rolled-up in great amount triggered by the intercalation of tiny droplet, taking advantage of a creative design of van der Waals interaction with substrate. The rolling of nanomembranes delaminated by liquid permits a wide choice in materials as well as precise manipulation in rolling direction by controlling the motion of microdroplet, resulting in intelligent construction of rolling microstructures with designable geometries. Moreover, this liquid-triggered delamination phenomenon and constructed microstructures are demonstrated in the applications among vapor sensing, microresonators, micromotors, and microactuators. This investigation offers a simple, massive, low-cost, versatile and designable construction of rolling microstructures for fundamental research and practical applications.

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