A High-Wet-Strength Biofilm for Readable and Highly Sensitive Humidity Sensors

Abstract

Low-cost and flexible biofilm humidity sensors with good wet strength are crucial for humidity detection. However, it remains a great challenge to integrate good reversibility, rapid humidity response, and robust humid mechanical strength in one sensor. In this respect, we report a facile method to prepare a sustainable biofilm (named MC film) from sisal cellulose microcrystals (MSF-g-COOH) and citric acid (CA). After crosslinking with CA, the MC film exhibits excellent wet strength and rapid humidity response. More importantly, MC film can be used over a wide temperature range with excellent durability and reversibility for humidity detection. A highly sensitive humidity sensor fabricated from the MC film exhibits high reversibility and excellent water resistance and can be applied in humidity and personalized breath health monitoring. Our work fills the gap between biomaterial design and high-performance sensing devices.

Multimodal Hydrogel‐Based Respiratory Monitoring System for Diagnosing Obstructive Sleep Apnea Syndrome

“…The severity of OSAS could be evaluated by the number and duration of apnea event per hour in the sleep respiratory monitoring, which was helpful for early diagnosis. Compared to other reported respiratory monitoring sensors that only depended on the result of single body part detection or single outputted electrical signal [1,15,16,20,25,[29][30][31][32][33][51][52] (Table S4, Supporting Information), this developed approach could highly exclude the interference of single factor, exhibiting much more accurate and convincing, which was ascribed from the dualmodal electrical signal output and simultaneously monitoring four different body parts, showing the great potential to be used in OSAS diagnosis.…”

A Dual‐Function Sensor for Highly Sensitive Detection of Flame and Humidity

“…Later, CA acted as a crosslinking agent to react with −OH from MgC and −NH 2 from SNF by a dehydration reaction (Figure S1b; Figures S4, and Figure S5, Supporting Information). [37,38] Finally, the MSCG films were obtained by an evaporation-induced self-crosslinking method (Figure 1j-k, 10 × 40 cm), which was used for the dual-functional sensor.…”

Harvesting Electricity from Atmospheric Moisture by Engineering an Organic Acid Gradient in Paper

“…As shown in the FTIR spectra (Figure b), compared to the original paper, the strong absorption peaks of the CA gradient paper at 1700 and 1740 cm –1 are attributed to the stretching vibrations of ester groups and unreacted carboxyl groups (CO) of CA, respectively, , and the peak at 778 cm –1 is assigned to the out-of-plane bending vibrations of CA (−OH), indicating that the −COOH groups were introduced to the paper. In addition, a new peak at 1238 cm –1 in the CA gradient paper is assigned to the ester group OC–O stretch band, which suggests the esterification reaction between the hydroxyl groups of cellulose and the carboxyl groups of CA . XPS patterns (Figure c) further confirmed the occurrence of the esterification reaction between CA and cellulose.…”

“…In addition, a new peak at 1238 cm −1 in the CA gradient paper is assigned to the ester group O�C−O stretch band, which suggests the esterification reaction between the hydroxyl groups of cellulose and the carboxyl groups of CA. 41 XPS patterns (Figure 2c) further confirmed the occurrence of the esterification reaction between CA and cellulose. The deconvolution C 1s of the CA gradient paper shows a new peak at ∼288.0 eV (O�C−O) compared to the original paper, indicating newly formed esters after CA treatment.…”