Date Published: January 09, 2019
Publisher: John Wiley and Sons Inc.
Author(s): Firoz Babu Kadumudi, Mohammadjavad Jahanshahi, Mehdi Mehrali, Tiberiu‐Gabriel Zsurzsan, Nayere Taebnia, Masoud Hasany, Soumyaranjan Mohanty, Arnold Knott, Brent Godau, Mohsen Akbari, Alireza Dolatshahi‐Pirouz.
Proteins present an ecofriendly alternative to many of the synthetic components currently used in electronics. They can therefore in combination with flexibility and electroactivity uncover a range of new opportunities in the field of flexible and green electronics. In this study, silk‐based ionic conductors are turned into stable thin films by embedding them with 2D nanoclay platelets. More specifically, this material is utilized to develop a flexible and ecofriendly motion‐sensitive touchscreen device. The display‐like sensor can readily transmit light, is easy to recycle and can monitor the motion of almost any part of the human body. It also displays a significantly lower sheet resistance during bending and stretching regimes than the values typically reported for conventional metallic‐based conductors, and remains fully operational after mechanical endurance testing. Moreover, it can operate at high frequencies in the kilohertz (kHz) range under both normal and bending modes. Notably, our new technology is available through a simple one‐step manufacturing technique and can therefore easily be extended to large‐scale fabrication of electronic devices.
Protein‐based components that are electrically active can open new exciting avenues in electronics because of their flexibility, greenness, lightness, and abundance.1, 2 Indeed, the replacement of conventional metallic‐based electronic components with such materials could potentially transform otherwise hard and rigid electronics into flexible and wearable electronics.1 However, protein‐based electronics still require additional consideration to enable them to resist the many demanding scenarios in nature and within the human body, as most of them quickly disintegrate in liquids and in response to various chemical and thermal stimuli. Since ionic conductors (ionics) can generate many exciting electronic devices3, 4, 5, 6, 7 and many protein‐based materials can be transformed into such mediators of electricity1, 8, 9, 10, 11, 12 a possible avenue for remedying these bottlenecks is via manufacture of water‐insoluble, thermally, and chemically stable protein films with high ionic conductivity.
In this work, we have showcased the many exciting properties of Fleco‐ionics, and utilized these exciting attributes to develop a wearable and green sensor. The Fleco‐like sensor was seamless in appearance, highly transparent and enabled human motion and touch detection capabilities. We accomplished this by transforming a protein‐based film made from silk (a natural ionic conductor) into a versatile and unusually stable material through the incorporation of inorganic, but yet green laponite. We coined this material SiPo and demonstrated that it was highly water‐insoluble as well as thermally and chemically stable this was attributed to a higher film crystallinity. Indeed, by simply increasing the laponite content in SiPo, we could significantly enhance its β‐sheet content and thus the crystallinity of the films.
Flexible and stretchable displays are currently being developed and marketed by Samsung and Sony, but these interfaces still do not provide combinatorial human–machine interactions. They also consist of highly expensive, toxic, and non‐recyclable components. Indeed, when such electronic devices are discarded they do not only possess a toxic threat for human habitats and those dwelling within them, but they are also increasing the demand for storage space that is increasingly difficult to find due to the growing global population.
Preparation of SiPo Thin Films: Silk fibroin was extracted from Bombyx Mori silk cocoons (Wild Fibers, UK). Briefly, 10 g of sliced silk cocoons were boiled in an aqueous solution of 0.02 m sodium carbonate (Na2CO3, Sigma‐Aldrich, Germany) for 30 min, in order to remove all traces of sericin. The obtained silk fibroin fibers were dried at room temperature for 24 h. The fibroin fibers were then dissolved in an aqueous solution of 9.3 m lithium bromide (LiBr, Honeywell, Germany) at 60 °C for 6 h, and subsequently dialyzed against deionized (DI) water for 3 days. To remove any impurities, the resultant fibroin solution was centrifuged for 20 min (three times) at 12 000 rpm with the temperature kept at 4 °C.
The authors declare no conflict of interest.