Pressure sensors are devices used to measure the pressure of liquids and gasses. Over the years, pressure sensors have been advanced to suit different applications in terms of sensitivity, sensing ranges and accuracy. Nonetheless, research on green electronic pressure sensing devices is less common. Despite being identified as promising solutions, paper pressure sensors are susceptible to several drawbacks that limit their properties and applications. For example, metal electrodes such as Ag and Ti, commonly used in the fabrication of paper pressure sensors, are not favorable for the fabrication of flexible and green electronic devices. Therefore, the fabrication of environmentally friendly, cost-effective and high-performance pressures sensors remains a challenge.
Besides low-cost and disposability, paper sensors also exhibit unique cutability and foldability advantages, which are very important for creating flexible geometries suitable for diverse applications. Developing paper pressure sensors that can be cut or folded into different patterns will allow them to be easily integrated with complex or hollow papers without affecting their original designs. Unfortunately, current paper-based devices have not demonstrated all these unique properties, mainly due to the limitations of the device’s configuration and applied metal electrodes.
On this account, Northeast Normal University researchers: Dr. Pengfei Zhao, Ruimin Zhang (Ph.D. Student), Professor Yanhong Tong, Professor Xiaoli Zhao, Professor Qingxin Tang, and Professor Yichun Liu demonstrated, for the fort time, an all-paper, all-organic, cuttable and foldable pressures sensors, to achieve all the unique advantages of paper-based sensors. Their research work is currently published in the journal, Advanced Electronic Materials.
In their approach, hollow and three-dimensional all-paper sensors were obtained through the fabrication of the kirigami or origami structures, that provide a universal strategy for the design of flexible devices. The team utilized a combination of multilayer porous low-conductivity polypyrrole (PPy) tissue paper as the active layer and high-conductivity polypyrrole printing paper as the electrode. The electrodes were placed in a sandwiched vertical configuration to improve the chances of fully achieving the advantages of all-paper and all-organic pressure sensors.
The authors reported that the new design fully demonstrated the unique advantages of paper-based pressure sensors, particularly, low cost, cutability, foldability, and flexibility. This could be attributed to the effective design configuration. Remarkably, the fabricated sensors exhibited high sensitivity, 4.8 kPa-1 at low pressures regimes and 1.7kPa-1 at high-pressure regimes, and high detection range of up to 40 kPa, comparable to the existing pressure paper sensors. The unique cutability and foldability of the device created unique three-dimensional capabilities allowing it to be freely cut and folded into two- and three-dimensional shapes desired for different applications.
In summary, the study is the first to demonstrate a feasible and cost-effective design approach to realize hollow structure and three-dimensional paper-based pressure sensors exhibiting all the unique advantages of paper. The high sensitivity and broad detection range could be attributed to microstructure induced by the printing electrodes and the multilayer tissue paper. Overall, the proposed design is advantageous in terms of cost, disposability, flexibility and suitable for fabricating green electronic devices. Additionally, the results demonstrate the potential applications of paper sensors in different fields, including monitoring various human physiological signals such as respiration and pulse detection. In a statement to Advances in Engineering, Professor Qingxin Tang noted that their research provided useful insights into the design and fabrication of cuttable and foldable pressure sensors and would pave the way for their applications in diverse fields.
Reference
Zhao, P., Zhang, R., Tong, Y., Zhao, X., Tang, Q., & Liu, Y. (2020). All‐Paper, All‐Organic, Cuttable, and Foldable Pressure Sensor with Tuneable Conductivity Polypyrrole. Advanced Electronic Materials, 6(8), 1901426.
