Thin compressive layers within a laminar ceramic arrest large cracks (surface and internal) and produce a threshold strength. This phenomenon increases the damage tolerance of ceramics and will allow engineers to design reliable ceramic components for structural applications. The stress intensity factor derived for a crack sandwiched between two compressive layers suggests that the threshold strength is proportional to the residual compressive stress and the thickness of the compressive layer and is inversely proportional to the distance between the compressive layers. Laminates composed of thick alumina layers (605 ± 11 micrometers) and thin mullite/alumina compressive layers (37 ± 1.4 micrometers) fabricated for this study had a threshold strength of 482 ± 20 megapascals, in fair agreement with the theory.

Dimensional reduction of electrospun P(VDF-TrFE) increases crystallinity (DOC), electroactive phase content (EA), Young’s modulus (E) and piezoelectric coefficient (d₃₃), collectively leading to enhanced piezoelectric energy harvesting efficiency.

Microneedle-based drug delivery has shown considerable promise for enabling painless transdermal and hypodermal delivery of conventional and novel therapies. However, this promise has yet to be fully realized due in large part to the limitations imposed by the micromechanical properties of the material systems being used. In this paper, we demonstrate titanium-based microneedle devices developed to address these limitations. Microneedle arrays with in-plane orientation are fabricated using recently developed high-aspect-ratio titanium bulk micromachining and multilayer lamination techniques. These devices include embedded microfluidic networks for the active delivery and/or extraction of fluids. Data from quantitative and qualitative characterization of the fluidic and mechanical performance of the devices are presented and shown to be in good agreement with finite-element simulations. The results demonstrate the potential of titanium micromachining for the fabrication of robust, reliable, and low-cost microneedle devices for drug delivery