Flexible and water-stable graphene-based electrodes for long-term use in bioelectronics.

We present the first demonstration of bioelectrodes made from laser-reduced graphene oxide (rGO) on flexible polyethylene terephthalate (PET) substrates that overcome two main issues: using hydrogel on skin interface with standard Ag/AgCl bioelectrodes vs. low signal to noise ratio with capacitance or dry electrodes. Today we develop a dry rGO bioelectrode technology with long-term stability for 100 h in harsh environments and when in contact with skin. Reliability tests in different buffer solutions with pH from 4.8 to 9.2 tested over 24 h showed the robustness of rGO electrodes. In terms of signal to noise ratio, our bioelectrodes performance is comparable to that of commercial ones. The bioelectrodes demonstrate an excellent signal to noise ratio, with a signal match of over 98% with respect to state-of-the-art electrodes used as a benchmark. We attribute the unique stability of our bioelectrodes to the rGO/PET interface modification and composite formation during laser processing used for GO reduction. The rGO/PET composite formation assertion is confirmed by mechanical stripping experiments and visual examination of re-exposed PET. The method developed here is simple, cost-effective, maskless, and can be scaled-up, allowing sustainable manufacture of arbitrary-shaped flexible electrodes for biomedical sensors and wearables.

On the optimal choice of a hyperelastic model of ruptured and unruptured cerebral aneurysm.

In the last decade, preoperative modelling of the treatment of cerebral aneurysms is being actively developed. Fluid-structure interaction problem is a key point of a such modelling. Hence arises the question about the reasonable choice of the model of the vessel and aneurysm wall material to build the adequate model from the physical point of view. This study covers experimental investigation of 8 tissue samples of cerebral aneurysms and 1 tissue sample of a healthy cerebral artery. Results on statistical significance in ultimate stress for the classification of 2 cohorts of aneurysms: ruptured and unruptured described earlier in the literature were confirmed (p ≤ 0.01). We used the four most common models of hyperelastic material: Yeoh, Neo-Hookean and Mooney-Rivlin (3 and 5 parameter) models to describe the experimental data. In this study for the first time, we obtained a classification of hyperelastic models of cerebral aneurysm tissue, which allows to choose the most appropriate model for the simulation problems requirements depending on the physical interpretation of the considered problem: aneurysm status and range of deformation.