Many functions of the human body manifest themselves in the form of mechanical deformation of the skin: it stretches,
In recent years, such movements have been tracked using wearable sensors; they can detect:
- high level tension (40-100%): movement of fingers, joints and limbs;
- medium tension (10–40%): swallowing and face movement;
- low level voltage (<1%–10%): pulse and vocal cord vibrations.
In order to provide the highestlevel of conductivity and stability, it is better to use PEDOT:PSS—this is a polymer mixture of two ionomers. One component in this mixture consists of sodium polystyrene sulfonate, which is sulfonated polystyrene. But the low stretchability of PEDOT:PSS films leads to deterioration in the performance of wearable devices based on it.
The authors of the new work have created a wearable device,which effectively detects different voltage levels. To maximize the stretchability of this sensor, they based it on the principles of snakeskin. Snakes can stretch to several times their normal body size, this happens because their skin is covered in overlapping scales. When voltage is applied, these scales slide over each other and are easily moved if necessary. Therefore, snake skin is extremely elastic.
Researchers used this design conceptwhen making your own sensor. They applied a thin layer of PEDOT:PSS and baked it with elastomeric tape. This layer was then stretched by 50%. This process resulted in the formation of cracks and microscopic pieces on the surface of the layer. These exposed areas served as bonding sites for the application of a second thin layer of PEDOT:PSS. After application, the second layer was further stretched to 100%. As a result, new stretches and islands were formed, which naturally coincided with the areas of the first layer.
According to the results of a number of experiments, the sensor producedWell-defined signals with a sensitivity range of two orders of magnitude. The signals accurately reflected degrees and angles of movement. In addition, the sensor demonstrated excellent conductivity and durability.
New development can be usedfor monitoring cardiac or circulatory functions, to assist people who have difficulty vocalizing or swallowing, and for physical rehabilitation or athletic performance assessment.
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