https://phys.org/news/2018-11-electroanatomical-non-thrombogenic-stretchable-multielectrode-arrays.html

Typically, multielectrode arrays (MEAs) are used to investigate the position of active/inactive cells, propagation of neural signals and networking among multiple neurons. The arrays can also be used to diagnose and treat disease by measuring biological signals at multiple points. The first reported in vitro MEA was fabricated on flat glass to measure cellular excitement in cultured myocardium, neuronal cells and propagation of signal from heart and brain slices. The recently developed noninvasive in vivo MEA arrays were fabricated on flexible plastic foil with the ability to contact soft and moving living tissues. During the engineering process, the device flexibility should be increased to facilitate MEAs onto complex structures in the body during implantation.

Conformal contact on wrinkled brain surfaces, for instance, can be achieved by reducing the device thickness below two µm. Similarly, ECG measurements can be conducted on the skin close to the heart via passive MEAs on 3 µm polyimide substrates. The ultraflexible properties of active MEAs were demonstrated via smooth contact to muscle cells, cerebral cortex as well as electromyography (EMG) and electrocorticography (ECoG) measurements. A stretchable and blood-compatible active MEA is yet to be realized due to two main limitations. At the onset, device degradation due to blood clots from surgical bleeding as a result of a high Young's modulus was seen with polyimide or parylene polymers despite their high compatibility. Thereafter, it is also difficult to engineer high-performance active elements with stretchability to measure biological signals. The active elements also required high amplification factors and low drive voltages.