Precision thermometry of the skin can, together with other measurements, provide clinically relevant information about cardiovascular health, cognitive state, malignancy and many other important aspects of human physiology. Here, we introduce an ultrathin, compliant skin-like sensor/actuator technology that can pliably laminate onto the epidermis to provide continuous, accurate thermal characterizations that are unavailable with other methods. Examples include non-invasive spatial mapping of skin temperature with millikelvin precision, and simultaneous quantitative assessment of tissue thermal conductivity. Such devices can also be implemented in ways that reveal the time-dynamic influence of blood flow and perfusion on these properties. Experimental and theoretical studies establish the underlying principles of operation, and define engineering guidelines for device design. Evaluation of subtle variations in skin temperature associated with mental activity, physical stimulation and vasoconstriction/dilation along with accurate determination of skin hydration through measurements of thermal conductivity represent some important operational examples.
Recent research in advanced materials and mechanics demonstrates the possibility for integrating inorganic semiconductors with soft, elastomeric substrates to yield systems with linear elastic mechanical responses to strains that signifi cantly exceed those associated with fracture limits of the constituent materials (e.g. ∼ 1% for many inorganics). This outcome can provide stretching to strain levels of tens of percent (in extreme cases, more than 100%), for diverse, reversible modes of deformation, including bending, twisting, stretching or compressing. [1][2][3][4][5][6][7] Interest in these outcomes is motivated by needs in fl exible display, [8][9][10] curvilinear imaging devices, [11][12][13] structural health monitors [ 14 ] and, more recently, in bio-integrated systems [15][16][17] for advanced therapeutic or diagnostic functionality in clinical medicine. In these latter applications, considerations related to toxicity and biocompatibility of the materials are also critically important. Some of the most well developed strategies exploit confi gurations in which brittle, rigid materials accommodate in-plane strains through out-of-plane motions, via buckling or twisting modes. [ 18 ] Such ideas can be exploited in all parts of an integrated system, or only in interconnections between active devices. The latter design can accommodate the largest strains, but its effi cacy decreases as the areal coverage of the devices increases. [ 12 ] As a result, important applications such as those in light capture (i.e., photovolatics) and detection (i.e., photodetectors), where high coverages are often desired, can be diffi cult to address. Here we report designs for stretchable systems that exploit elastomeric substrates with surface relief that confi nes strains at the locations of the interconnections, and away from the devices. The results enable areal coverages and levels of stretchability with relatively low interfacial stress between devices and substrates, compared to similar layouts with conventional, fl at substrates. We describe, using a combination of theory and experiment, the essential mechanics, and then demonstrate the ideas in stretchable solar modules that use ultrathin, single junction GaAs solar cells.A representative layout for a structured substrate designed for this purpose appears in Figure 1 , in which the relief consists of isolated, raised regions (i.e. islands) separated by recessed features (i.e. trenches). The casting and curing processes of soft lithography [ 19 ] provide a convenient means to form such relief, with excellent dimensional control, in elastomers such as poly(dimethylsiloxane) (PDMS). The image of Figure 1a provides a cross sectional view for a representative case where square islands with edge lengths ( l island ) of 800 μ m are separated by trenches with widths ( l trench ) and depths ( h trench ) of 156 μ m and 200 μ m, respectively. The thickness of the underlying PDMS (i.e. base) is 200 μ m. This type of structure is attractive for stretchable systems that incorporate no...
The aim of the present study was to determine the effects of metformin, combined with a p38 mitogen-activated protein kinase (MAPK) inhibitor, on the sensitivity of cisplatin-resistant ovarian cancer to cisplatin. The expression and distribution of phosphorylated p38 MAPK (P-p38 MAPK) was confirmed in drug-resistant and primary ovarian cancer tissues by immunohistochemistry and western blotting. A bromodeoxyuridine ELISA kit was used to analyze the effects of metformin, SB203580, a p38 MAPK inhibitor, and metformin combined with SB203580, on the cell proliferation of SKOV3/DDP cisplatin-resistant ovarian cancer cells. The protein expression of P-p38 MAPK was significantly higher in cisplatin-resistant ovarian cancer, as compared with the primary ovarian cancer tissues. Metformin combined with SB203580 significantly enhanced the sensitivity of SKOV3/DDP cells to cisplatin. In conclusion, the p38 MAPK signaling pathway may be associated with cisplatin-resistant ovarian cancer. Metformin, combined with the p38 MAPK inhibitor, significantly increased the sensitivity of SKOV3/DDP cells to cisplatin treatment.
Smart adhesives possess a wide range of applications owing to their reversibly and repeatedly switchable adhesion in transfer technology. Despite recent advances, it still remains a technical and scientific challenge to achieve strategies for rapidly tunable adhesion in a noncontact manner. In this study, a smart adhesive to achieve dynamically tunable adhesion is developed. Specifically, a mushroom‐shaped adhesive with a magnetized tip is actuated to reversibly and rapidly transform the morphology via magnetic actuation. The smart adhesive has two working modes, namely, selective pickup mode and pick‐and‐place mode. In the selective pickup mode, the external magnetic field is applied and the tip undergoes bending deformation. Changes in tip morphology allow for a reversible switch of the adhesion between “turn on” and “turn off.” In the pick‐and‐place mode, the external magnetic field is applied when the target object needs to be released. Upward bending deformation of the micro‐beam, a part of the tip, creates an initial crack at the edge of the adhesion interface. The propagation of the edge crack modulates the adhesion from strong to weak and the target object is instantly released. The proposed smart adhesive may be of interest for practical applications demanding highly precise and swiftly controlled movements.
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