In the latest article from Small, “3D Printing of Thermo‐Mechano‐Responsive Photoluminescent Noncovalent Cross‐Linked Ionogels with High‐Stretchability and Ultralow‐Hysteresis for Wearable Ionotronics and Anti‐Counterfeiting,” researchers presented a unique strategy for creating highly stretchable ionogels. By utilizing a phase separation method, they managed to 3D print 2-hydroxypropyl acrylate (HPA) in 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4), resulting in ionogels that show significant promise for various applications. These ionogels exhibit a range of beneficial properties, including remarkable stretchability, ultra-low hysteresis, and unique thermochromic and photoluminescent features.
Innovative Strategy and Performance
The innovative technique employed involves fabricating noncovalent cross-linked ionogels through phase separation, which is achieved by 3D printing HPA in BMIMBF4. This method results in ionogels with a sea-island structure, comprising smaller nanodomains and larger nanodomain clusters. This structure is crucial in reducing energy dissipation, thereby enhancing the stretchability (>1000%) and minimizing hysteresis to as low as 0.2%. Additionally, these ionogels demonstrate excellent temperature tolerance, ranging from -33°C to 317°C, and maintain extraordinary ionic conductivity up to 1.7 mS cm-1.
Another significant finding is the durability of these ionogels, which can withstand up to 5000 cycles. The formation of a nanophase separation and cross-linking structure further endows these ionogels with unique thermochromic and multiple photoluminescent properties. These characteristics are particularly suitable for applications in anti-counterfeiting and encryption.
Applications in Ionotronic Sensors
The research has also led to the development of flexible thermo-mechano-multimodal visual ionotronic sensors. These sensors are capable of strain and temperature sensing, providing stable and reproducible electrical responses over 20,000 cycles. The synergistic optical and electrical output performances make these sensors highly valuable in various practical applications.
Previous reports have highlighted the potential of ionogels but often faced challenges such as low stretchability and significant hysteresis. These issues limited their mechanical stability and repeatability. The latest approach addresses these limitations by creating ionogels with enhanced properties, making them more suitable for advanced applications.
Comparing earlier research, where ionogels were often plagued by mechanical instability, the current findings represent a notable improvement. Earlier methods did not achieve the same level of durability and performance consistency, particularly in extreme temperature conditions. The integration of phase separation and 3D printing techniques marks a significant step forward in the development of functional ionogels.
Looking ahead, these multifunctional ionogels have the potential to revolutionize the field of wearable ionotronics and anti-counterfeiting technologies. The combination of high stretchability, low hysteresis, and unique optical properties makes them well-suited for applications requiring both flexibility and durability. Further research could explore additional applications and improve the scalability of the production process for broader commercial use.
