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• Hydroxyapatite (HAP) composite paper with biocompatibility and hygroscopicity was prepared. • HAP composite paper has better hygroscopic and triboelectric properties than pure paper, making it more suitable for wearable sensing applications. • The HAP composite paper-based triboelectric nanogenerator can detect and distinguish different joint movements. • Hemostatic and disposable HAP composite paper can be degraded in the natural environment without harm. Wearable triboelectric nanogenerators (TENGs) have attracted considerable attention in the field of self-powered sensors that can be worn on the skin directly without packaging because of their breathability, conformability, and sensitivity to collect biomechanical energy. However, high humidity on the skin can affect the wearable TENG output performance, substantially affecting the sensor performance and stability. When worn for a long time, humidity can even cause skin inflammation. Thus, for a wearable TENG, moisture control and biocompatibility are also key factors that need to be addressed. Herein, we report a hygroscopic and biocompatible paper-based TENG using a hydroxyapatite (HAP) mineral coating to enhance the paper fiber. The mineral coating can maintain the surface of the paper fiber, which will not cause large external deformation of the paper fiber under a force, avoid squeezing out excess water, and keep the friction surface dry, avoiding humidity affecting the output performance. Without interfering with the performance of the TENG, the maximum water absorption of the HAP composite paper is ∼8 μL. The HAP composite paper–based TENG (4 cm2) has an open-circuit voltage and short-circuit current 5.8 times and 4.2 times that of pure paper, respectively, and can obtain 80.4 mW/m2 output and directly light 117 LEDs. At relative humidity values of 25.7 %, 43.1 %, and 58.8 %, the performance retained the peak values of 80.2 %, 68 %, and 63.7 %, respectively. Even at a high relative humidity of 71.7 %, the triboelectric performance of HAP composite paper is retained 59.3 %, and the stability under humidity is better than that of pure paper (45.6 %). In addition, the mineral paper can even work with tissue fluid and output performance decreases by 43.8 %. The mineral-enhanced paper TENG with high power generation performance, hygroscopicity, biocompatibility, and degradability provides a new perspective for disposable wearable sensors, even in medical treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • Multi-layer forming technology can integrate triboelectric material with electrode. • The all CPTENGs can exhibit excellent humidity, acid and alkali resistance. • The CPTENGs can yield a V OC , I SC and power density of 227.1 V, 6.9 μA and 520 mW/m2. • Matching CPTENGs with P-ZISC can obtain a self-charging power system (PSCPS). • The PSCPS can drive some miniaturized electronics for a long time. Triboelectric nanogenerators (TENGs) are regarded as a promising technology to drive the development of flexible/wearable electronics and self-powering sensor. Application of cellulose paper as the triboelectric positive materials makes TENGs more environmentally friendly. However, the limited output performance and stability in harsh environments and oxidation and corrosion of the metal electrodes have limited the practical application of cellulose paper based triboelectric nanogenerators (CPTENGs). Here, we have integrated cellulose paper-based triboelectric material and electrode in one sheet by using multi-layer forming technology in paper industry; the upper triboelectric layer shows excellent triboelectric positive performance, hydrophobicity and acid and alkali resistance, while the bottom electrode exhibits promise conductivity. The all CPTENGs can yield a maximum open-circuit voltage (V OC) of 227.1 V, a short-circuit current (I SC) of 6.9 μA. Furthermore, the V OC values of the all CPTENGs increase from 0.02 V to 225.1 V at the load resistance of 100 Ω∼10 GΩ; and a power density of 520 mW·m−2 is also obtained at a load resistance of 30 MΩ. Moreover, the V OC of CPTENGs not only retains up to 78 % of its initial value at a high relative humidity of 90 %, but also almost maintains unchanged in a wide range of the pH environment (pH = 1∼13). More importantly, the CPTENGs can be readily matched with paper-based zinc supercapacitor (P-ZISC) to act as an all paper based self-charging power system (PSCPS). The PSCPS is capable of driving various miniaturized electronics, such as electronic watch, temperature/humidity indicator, demonstrating its potential application in a sustainable power source for portable and green electronics. [ABSTRACT FROM AUTHOR]

Triboelectric nanogenerators (TENGs) have been investigated as a promising device to harvest mechanical energy into electricity. At present, paper-based triboelectric nanogenerators (P-TENGs) have been widely researched because paper features with lightweight, low cost, abundance, renewability and biodegradability. In this paper, the operating principles and operation modes of TENGs, the development progress and performance enhancement routes of P-TENGs are comprehensively reviewed. Additionally, the overview, challenges and opportunities of P-TENGs applications are also presented. [ABSTRACT FROM AUTHOR]

• Ultrasensitive detection limit can reach as low as 0.01 ppm for riboflavin. • Just need a single droplet for detection using this indicator paper. • In-situ dual detection of riboflavin and pH with same droplet and indicator paper. • Excellent self-clean property makes droplet easy to remove and brings recyclability. Traditional indicator paper is disposable after use, requires a large number of target solutions and can only detect one item. In this study, recyclable upconversion-fluorescence indicator papers consist of upconversion nanorods and plasmonic nanostructures are fabricated by electrospinning. Human-body fluids containing different riboflavin concentration and pH are used as target solution, because these two items are usually detected in clinic to distinguish ambiguous diseases but often performed by two different testing processes that inevitably need more target solutions. Significantly different from conventional detecting system, this recyclable indicator paper can simultaneously achieve riboflavin and pH detections by using only a single droplet of target solution. As low as 0.01 ppm riboflavin can be sensitively detected, which is superior to most reported detection limit of fluorescence sensor. Moreover, this indicator paper can detect a single droplet (~10 μl) rather than a large amount of target solution (>1 ml) needed by traditional detecting system, and the pH can also be simultaneously in-situ detected using the same indicator paper. After the detection, the target solution is easily removed so that it brings about excellent recyclability, which is another advantage over traditional detecting system. [ABSTRACT FROM AUTHOR]