Stretchable and Conductive Cellulose/Conductive Polymer Composite Films for On-Skin Strain Sensors

Innovative Application of Salophen Derivatives in Organic Electronics as a Composite Film with a Poly(3,4-Ethylenedioxythiophene)-poly(styrenesulfonate) Matrix

In this work, we present the innovative synthesis of salophen (acetaminosalol) derivatives in a solvent-free environment by high-speed ball milling, using a non-conventional activation method, which allowed obtaining compounds in a shorter time and with a better yield. Furthermore, for the first time, the salophen derivatives were deposited as composite films, using a matrix of poly 3,4-ethylene dioxythiophene:polystyrene sulfonate (PEDOT:PSS) polymer. Significant findings include the transformation from the benzoid to the quinoid form of PEDOT post-IPA treatment, as evidenced by Raman spectroscopy. SEM analysis revealed the formation of homogeneous films, and AFM provided insights into the changes in surface roughness and morphology post-IPA treatment, which may be crucial for understanding potential applications in electronics. The optical bandgap ranges between 2.86 and 3.2 eV for PEDOT:PSS-salophen films, placing them as organic semiconductors. The electrical behavior of the PEDOT:PSS-salophen films undergoes a transformation with the increase in voltage, from ohmic to space charge-limited conduction, and subsequently to constant current, with a maximum of 20 mA. These results suggest the possible use of composite films in organic electronics.

Recent progress and applications of cellulose and its derivatives-based humidity sensors: A review

Cellulose and its derivatives, which are low-cost, degradable, reproducible and highly hydrophilic, can serve as both substrate and humidity sensitive materials, making them more and more popular as ideal biomimetic materials for humidity sensors. Benefiting from these characteristics, cellulose-based humidity sensors cannot only exhibit high sensitivity, excellent mechanical performance, wide humidity response range, etc., but also can be applied to fields such as human health, medical care and agricultural product safety monitoring. Herein, cellulose-based humidity sensors are first classified according to the different conductive active materials, such as carbon nanotubes, graphene, electrolytes, metal compounds, and polymer materials, based on which the latest research progress is introduced, and the roles of different types of conductive materials in cellulose-based humidity sensors are analyzed and summarized. Besides, the similarities and differences in their working mechanisms are expounded. Finally, the application scenarios of cellulose-based humidity sensors in human movement respiration and skin surface humidity monitoring are discussed, which can make readers quickly familiarize the current preparation method, working mechanism and subsequent development trend of cellulose-based humidity sensors more effectively.

Paper-Based Humidity Sensor for Respiratory Monitoring

Flexible respiratory monitoring devices have become available for outside-hospital application scenarios attributable to their improved system wearability. However, the complex fabrication process of such flexible devices results in high prices, limiting their applications in real-life scenarios. This study proposes a flexible, low-cost, and easy-processing paper-based humidity sensor for sleep respiratory monitoring. A paper humidity sensing model was established and sensors under different design parameters were processed and tested, achieving high sensitivity of 5.45 kΩ/%RH and good repeatability with a matching rate of over 85.7%. Furthermore, the sensor patch with a dual-channel 3D structure was designed to distinguish between oral and nasal breathing from origin signals proved in the simulated breathing signal monitoring test. The sensor patch was applied in the sleep respiratory monitoring of a healthy volunteer and an obstruct sleep apnea patient, demonstrating its ability to distinguish between different respiratory patterns as well as various breathing modes.