approach to fabricate 1.64 µm-thin black-gold fi lms on any elastomeric sheet (latex rubber, Eco-fl ex, polydimethylsiloxane (PDMS), etc.) resulting in highly stretchable strain sensors. The ultrathin sensors could detect strains as small as 0.01% and as large as 350%, simultaneously with a typical GF of 6.9-9.9, a fast response (<22 ms). We observed negligible loadingunloading signal changes over 5000 cycles. The superior sensing performances enabled real-time monitoring of a wide range of human motions (fore arm muscle movement, cheek motions, throat muscle stretching, and fi nger fl exion extension as well as human radial artery pulse).The fabrication process of AuNWs strain sensors is illustrated in Figure 1 a. First, a AuNWs solution (10 mg mL −1 ) was prepared following the previously published protocol. [ 38 ] Second, a latex rubber sheet was sandwiched between a fl at glass slide and a polyimide mask with a rectangular opening (25 × 5 mm 2 ). Then AuNWs solution (100 µL) was dropcasted onto the open area of polyimide mask and dried. After removing the glass slide and polyimide mask, a conductive AuNWs strip fi lm was obtained with a typical sheet resistance of 2.03 ± 0.95 MΩ.The AuNWs strip-fabrication approach was general, which could be extended to a variety of other polymeric substrates (PET, Eco-fl ex, PDMS, nitrile rubber, etc.) with uniform deposition and strong adhesion (Figure 1 b). After electrically wiring the AuNWs strip with two conductive threads, a skin-attachable and highly stretchable strain sensor was obtained (Figure 1 c). The conductive AuNWs fi lms were about 1.64 µm in thickness (Figure 1 c, top right), and with a top surface of nanowire-entangling and bundling morphologies resembling polymeric chains (Figure 1 c, bottom right).The thin AuNWs fi lms exhibited outstanding mechanical stretchability up to 300% without any observable cracking or fi lm detachment from latex rubber (Movie 1, Supporting Information). It also showed exceptional electrical conductivity recovery, superior to their corresponding sputter-coated gold fi lm or silver nanowires fi lm (Figure 1 d). The electrical resistance of AuNWs fi lm increased gradually and smoothly as the strain increased and recovered gradually and smoothly to the original conductivity as the strain was revered back to 0%. Such a fully reversible process was observed under a dynamic strain of 0%-100%-0% and almost no hysteresis was observed (Figure 1 d). In contrast, the sputter coated gold fi lm became completely insulative when the strain was over 30%, and remained insulative even when the strain was removed (0% strain) (Figure 1 e). It was also observed that irreversible cracks formed during stretching.Further investigation on silver nanowires (AgNWs) fi lm prepared by drop casting showed that its conductivity was lost Highly stretchable strain sensors will be key components in future wearable electronics with broad applications ranging from electronic skins, [1][2][3][4][5][6][7][8][9][10] intelligent human/machine interactions, [ 11,12 ]...

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We introduce Plasmene- in analogy to graphene-as free-standing, one-particle-thick, superlattice sheets of nanoparticles ("meta-atoms") from the "plasmonic periodic table", which has implications in many important research disciplines. Here, we report on a general bottom-up self-assembly approach to fabricate giant plasmene nanosheets (i.e., plasmene with nanoscale thickness but with macroscopic lateral dimensions) as thin as ∼40 nm and as wide as ∼3 mm, corresponding to an aspect ratio of ∼75,000. In conjunction with top-down lithography, such robust giant nanosheets could be milled into one-dimensional nanoribbons and folded into three-dimensional origami. Both experimental and theoretical studies reveal that our giant plasmene nanosheets are analogues of graphene from the plasmonic nanoparticle family, simultaneously possessing unique structural features and plasmon propagation functionalities.