Triggerable transient electronics are demonstrated with the use of a metastable poly(phthalaldehyde) polymer substrate and encapsulant. The rate of degradation is controlled by the concentration of the photo-acid generator and UV irradiance. This work expands on the materials that can be used for transient electronics by demonstrating transience in response to a preselected trigger without the need for solution-based degradation.
Thermally triggered transient electronics using wax-encapsulated acid, which enable rapid device destruction via acidic degradation of the metal electronic components are reported. Using a cyclic poly(phthalaldehyde) (cPPA) substrate affords a more rapid destruction of the device due to acidic depolymerization of cPPA.
When pure alumina is sintered at 1620°C, normal grain growth occurs with equiaxial grains and curved grain boundaries. When 100 ppm of SiO 2 together with 50 ppm of CaO is added, abnormal grain growth (AGG) occurs with large grains elongated with straight grain-boundary segments in the direction of the basal planes. Some of the fine matrix grains also have straight grain boundaries, and ϳ10% of the grain boundaries of the matrix grains are faceted when observed by transmission electron microscopy (TEM). Some of these grain boundaries are expected to be singular with low-energy structures corresponding to the cusps in the polar plot of the grain-boundary energy against the inclination angle. No frozen liquid is found at the grain triple junctions and grain boundaries by TEM. When 600 ppm of MgO is added together with 100 ppm of SiO 2 and 50 ppm of CaO normal growth occurs. The grain boundaries are curved when observed via optical microscopy and TEM and show that all the grain boundaries are defaceted, indicating that they become atomically rough. When sintered at 1900°C after adding 150, 300, or 500 ppm of SiO 2 , AGG occurs with straight and faceted grain boundaries, similar to the specimens sintered at 1620°C after CaO and SiO 2 are added. When MgO is added together with SiO 2 and sintered at 1900°C, normal grain growth occurs with rough grain boundaries. High-resolution TEM observation shows no frozen liquid layer at a grain boundary. The results indicate that the occurrence of AGG in alumina with SiO 2 or together with CaO is correlated with the formation of faceted and straight (on large and atomic scales) grain boundaries. It is proposed that these grain boundaries have singular ordered structures with low boundary energies and their growth by lateral step movement can cause the AGG. The addition of MgO causes grain-boundary roughening and, thus, normal grain growth. The grain boundaries in pure alumina also appear to be rough, and, hence, normal grain growth occurs.
The ability to image pressure distribution over complex three-dimensional surfaces would significantly augment the potential applications of electronic skin. However, existing methods show poor spatial and temporal fidelity due to their limited pixel density, low sensitivity, or low conformability. Here, we report an ultraflexible and transparent electroluminescent skin that autonomously displays super-resolution images of pressure distribution in real time. The device comprises a transparent pressure-sensing film with a solution-processable cellulose/ nanowire nanohybrid network featuring ultrahigh sensor sensitivity (>5000 kPa −1 ) and a fast response time (<1 ms), and a quantum dot-based electroluminescent film. The two ultrathin films conform to each contact object and transduce spatial pressure into conductivity distribution in a continuous domain, resulting in super-resolution (>1000 dpi) pressure imaging without the need for pixel structures. Our approach provides a new framework for visualizing accurate stimulus distribution with potential applications in skin prosthesis, robotics, and advanced human-machine interfaces.
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