Publications by authors named "Julio A Iglesias Martinez"
Non-Newtonian liquids are characterized by stress and velocity-dependent dynamical response. In elasticity, and in particular, in the field of phononics, reciprocity in the equations acts against obtaining a directional response for passive media. Active stimuli-responsive materials have been conceived to overcome it.
View Article and Find Full Text PDFThe ability to significantly change the mechanical and wave propagation properties of a structure without rebuilding it is currently one of the main challenges in the field of mechanical metamaterials. This stems from the enormous appeal that such tunable behavior may offer from the perspective of applications ranging from biomedical to protective devices, particularly in the case of micro-scale systems. In this work, a novel micro-scale mechanical metamaterial is proposed that can undergo a transition from one type of configuration to another, with one configuration having a very negative Poisson's ratio, corresponding to strong auxeticity, and the other having a highly positive Poisson's ratio.
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- In solid state physics, phase transitions can change material properties and functionality, especially in mechanical metamaterials where structural changes can occur due to instability.
- A new 3D mechanical metamaterial has been designed to undergo an elastic phase transition from positive to negative Poisson's ratio under compression while maintaining Young's modulus stability, addressing limitations in previous designs.
- The metamaterial is created using two-photon lithography at a micro-scale, and it demonstrates auxetic behavior, meaning it can expand laterally when compressed, over a wide range of applied strains.
Three-dimensional direct laser writing technology enables one to print polymer microstructures whose size varies from a few hundred nanometers to a few millimeters. It has been shown that, by tuning the laser power during writing, one can adjust continuously the optical and elastic properties with the same base material. This process is referred to as gray-tone lithography.
View Article and Find Full Text PDFShape morphing and the possibility of having control over mechanical properties via designed deformations have attracted a lot of attention in the materials community and led to a variety of applications with an emphasis on the space industry. However, current materials normally do not allow to have a full control over the deformation pattern and often fail to replicate such behavior at low scales which is essential in flexible electronics. Thus, in this paper, novel 2D and 3D microscopic hierarchical mechanical metamaterials using mutually-competing substructures within the system that are capable of exhibiting a broad range of the highly unusual auxetic behavior are proposed.
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- The study reports the first direct observation of roton-like dispersion relations in three-dimensional metamaterials under normal conditions, expanding beyond previously studied systems like superfluid helium.
- Two distinct experiments demonstrate this phenomenon: one with transverse elastic waves in microscale metamaterials using ultrasound frequencies, and another with longitudinal air-pressure waves in larger channel-based metamaterials at audible frequencies.
- The findings highlight the significance of engineered interactions in metamaterials to manipulate the lowest dispersion branch, which contrasts with previous research focused on higher dispersion branches.