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Metamaterials are rationally designed composites made of building blocks which are composed of one or more constituent materials. Metamaterial properties can go beyond those of the ingredient materials, both qualitatively and quantitatively. In addition, their properties can be mapped on some generalized continuum model. We present the general procedure of designing elastic metamaterials based on masses and springs. We show that using this simple approach we can design any set of effective properties including linear elastic metamaterials,—defined by bulk modulus, shear modulus, mass density—and nonlinear metamaterials,—with instabilities or programmable parts. We present designs and corresponding numerical calculations to illustrate their constitutive behavior. Finally, we discuss the addition of a thermal stimulus to mechanical metamaterials.

Background: Complete fading of port wine stains (PWS) is difficult to achieve with current laser treatments. Photodynamic therapy (Gu's PDT) could offer a very efficient alternative for PWS therapy., Patients and Method: 1949 lesions in 1385 patients were treated by PDT. Each patient received an intravenous injection of hematoporphyrin derivative (HpD) or hematoporphyrin monomethyl ether (HMME) at 3-7 mg/kg. Laser irradiation was performed on a 2 to 8 cm spot size. Different wavelengths (488.0 nm to 578.2 nm) were evaluated with a power density of 50-100 mW/cm2. Fluences ranged from 90 to 540 J/cm2., Results: Among the 1942 lesions, PWS clearance was observed in 99.7% of cases. Excellent results were achieved in 128 lesions (6.6%) (100% clearance), 746 lesions (38.3%) yielded to good results (clearance > 75%), 923 lesions (47.4%) showed moderate results (clearance 50-75%), 145 lesions (7.4%) showed poor results (clearance<50%) and in 7 lesions (0.3%) no visible change was observed. The pink port wine stains revealed better response to Gu's PDT with only one session. Conversely, purple stains in adult patients required 2 sessions or more., Conclusion: This new PDT technique is effective and highly selective, with almost no risk of scarring.