Manufacturing biodegradable lignocellulosic films with tunable properties from spent coffee grounds: A sustainable alternative to plastics.

Manufacturing biodegradable lignocellulosic films from spent coffee grounds (SCG) as an alternative to commercial plastics is a viable solution to address plastic pollution. Here, the biodegradable lignocellulosic films from SCG were fabricated via a sequential alkaline treatment and ionic liquid-based dissolution process. The alkaline treatment process could swell the cell wall of SCG, change its carbohydrates and lignin contents, and enhance its solubility in ionic liquids. The prepared SCG films with different lignin contents exhibited outstanding UV blocking capability (42.07-99.99 % for UVB and 20.96-99.99 % for UVA) and light scattering properties, good surface hydrophobicity (water contact angle = 63.2°-88.7°), enhanced water vapor barrier property (2.28-6.79 × 10-12 g/m·s·Pa), and good thermal stability. Moreover, the SCG films exhibit excellent mechanical strength (50.10-81.56 MPa, tensile strength) and biodegradability (fully degraded within 30 days when buried in soil) compared to commercial plastic. The SCG films represent a promising alternative that can replace non-biodegradable plastics.

All-Wood-Based Ionic Power Generator with Dual Functions for Alkaline Wastewater Reuse and Energy Harvesting.

Water-induced electricity harvesting has gained much significance for energy sustainability. Bio-based hydrovoltaic materials increase the attractiveness of this strategy. Although promising, it faces a challenge due to its reliance on fresh water and its inherently low power output. Herein, the energy from alkalinity-gradient power generation demonstrated the feasibility of reuse of alkaline wastewater to develop an all-wood-based water-induced electric generator (WEG) based on ion concentration gradients. The intermittent water droplets bring about uneven distribution of electrolyte and endow delignified wood with the difference of ion concentration along aligned cellulose nanochannels, thus supplying electrical power. The practice of using alkali reservoirs, including industrial wastewater, further contributes to electricity generation. The cubic WEG with a side length of 2 cm can produce an ultrahigh open-circuit voltage of about 1.1 V and a short-circuit current of up to 320 µA. A power output of 6.75 µW cm-2 is correspondingly realized. Series-connected WEGs can be used as an energy source for commercial electronics and self-powered systems. Our design provides a double value proposition, allowing for sustainable energy generation and wastewater reuse.

Making commercial bracelet smarter with a biochemical button module.

Despite the rapid development of mobile health based on wearable devices in recent years, lack of access to biochemical detection remains a vital challenge for most commercial wearable devices, which hinders the provision of effective electronic health records (EHRs) for disease control strategies, and further constraining the development of personalized precision medicine. Herein, we propose a strategy to graft biochemical detection function onto commercial bracelet. Different from the conventional development process of designing a completely new wearable biochemical device, we prefer to upgrade existing commercial wearable device to achieve simpler, faster, and more effective research and commercialization processes. An affordable and user-friendly biochemical button module has been designed that enables to integrate sensitive, specific, and rapid biochemical detection function into the idle space on the strap of the bracelet without increasing the size of the main body. This "Smart Bracelet Plus" shows the ability to simultaneously monitor physical and biochemical signals, and will serve as a reliable and systematic personal diagnostics and monitoring platform for providing real-time EHRs for disease control strategies and improving the efficiency of the healthcare system.

A novel premixing strategy for highly sensitive detection of nitrite on paper-based analytical devices.

BACKGROUND: Nitrite has been involved in many food processing techniques and its excessive consumption is closely related to the development of different diseases. Therefore, highly sensitive detection of nitrite is significant to ensure food safety. RESULT: This study presents a simple and novel strategy for the highly sensitive detection of nitrite in food using paper-based analytical devices (PADs). In this proposed strategy, the nitrite present in the sample undergoes efficient diazotization when initially mixed with sulfanilamide solution before reacting with N-(1-naphthyl) ethylenediamine dihydrochloride (NED) coated on the detection region of the PAD, leading to the maximum production of colored azo compounds. Specifically, within the concentration range of 0.1-20 mg/L, the LOD and LOQ for the nitrite assay using the premixing strategy are determined as 0.053 mg/L and 0.18 mg/L, respectively which significantly surpass the corresponding values of 0.18 mg/L (LOD) and 0.61 mg/L (LOQ) achieved with the regular Griess reagent analysis. SIGNIFICANCE: The study highlights the critical importance of the premixing strategy in nitrite detection. Under optimized conditions, the strategy demonstrates an excellent limit of detection (LOD) and limit of quantification (LOQ) for nitrite detection in eight different meat samples. In addition to its high precision, the strategy is applicable in the field of nitrite analysis. This strategy could facilitate rapid and cost-effective nitrite analysis in real food samples, ensuring food safety and quality analysis.

Fabrication of biodegradable films with UV-blocking and high-strength properties from spent coffee grounds.

Utilizing spent coffee grounds (SCG) to produce high value-added materials is attractive and meaningful. In this work, a multi-functional biomass film is prepared from SCG and dissolving pulp through a dissolution and regeneration process. Importantly, dissolving pulp as a reinforcing additive can significantly enhance the mechanical strength of the regenerated SCG film. The prepared composite films with SCG contents ranging from 33.33 wt% to 81.82 wt% demonstrate excellent optical and mechanical properties. The composite film with 66.67 wt% SCG exhibits outstanding UV blocking capability (99.43 % for UVB and 96.59 % for UVA) and high haze (69.22%); meanwhile, the composite film with 33.33 wt% SCG performs better mechanical strength (58.69 MPa tensile strength and 3.13 GPa Young's modulus) and superior biodegradability (fully degraded within 26 days by being buried in soil) than commercial plastic. This work generally introduces a facile and practical approach to converting waste SCG into promising materials in various fields.

Development of a pumpless acoustofluidic device for rapid food pathogen detection.

Mixing, homogenization, separation, and filtration are crucial processes in miniaturized analytical systems employed for in-vitro biological, environmental, and food analysis. However, in microfluidic systems achieving homogenization becomes more challenging due to the laminar flow conditions, which lack the turbulent flows typically used for mixing in traditional analytical systems. Here, we introduce an acoustofluidic platform that leverages an acoustic transducer to generate microvortex streaming, enabling effective homogenizing of food samples. To reduce reliance on external equipment, tubing, and pump, which is desirable for Point-of-Need testing, our pumpless platform employs a hydrophilic yarn capable of continuous wicking for sample perfusion. Following the homogenization process, the platform incorporates an array of micropillars for filtering out large particles from the samples. Additionally, the porous structure of the yarn provides a secondary screening mechanism. The resulting system is compact, and reliable, and was successfully applied to the detection of Escherichia coli (E. coli) in two different types of berries using quantitative polymerase chain reaction (qPCR). The platform demonstrated a detection limit of 5 CFU g-1, showcasing its effectiveness in rapid and sensitive pathogen detection.

3D-printed solar evaporator with seashell ornamentation-inspired structure for zero liquid discharge desalination.

Solar-driven interfacial evaporation has enormous promise for fresh water recovery and salt harvesting, but salt accumulation-related challenges stand in its way. Herein, we report a spined groove-ridge pairs inspired by the shell ornamentation of the Vasticardium vertebratum, which addresses salt accumulation by artfully integrating salt reflux into localized salt crystallization. The seashell-mimetic radial V-groove array enables the 3D evaporator to transport water rapidly and directionally, resulting in high-performance water evaporation (∼95% efficiency) and localized crystallization. The periodic spines enlightened by the spine-bearing ridge on the seashell provide considerable micro-unit salt reflux. The 2-in-1 integration design endows the three-dimensional evaporator with superior solar-driven zero liquid discharge and excellent long-term salt resistance even when dealing with high-salinity brine (20 wt% NaCl) and a series of heavy metallic salt solutions. Our design offers a new alternative solution to avoiding salt scaling and could advance locally crystallized solar evaporators towards practical applications.

Surface-Enhanced Raman Spectroscopy Substrates for Food Safety and Quality Analysis.

Surface-enhanced Raman spectroscopy (SERS) has been identified as a fundamental surface-sensitive technique that boosts Raman scattering by adsorbing target molecules on specific surfaces. The application of SERS highly relies on the development of smart SERS substrates, and thus the fabrication of SERS substrates has been constantly improved. Herein, we investigate the impacts of different substrates on SERS technology including plasmonic metal nanoparticles, semiconductors, and hybrid systems in quantitative food safety and quality analysis. We first discuss the fundamentals, substrate designs, and applications of SERS. We then provide a critical review of the recent progress of SERS in its usage for screening and detecting chemical and biological contaminants including fungicides, herbicides, insecticides, hazardous colorants, and biohazards in food samples to assess the analytical capabilities of this technology. Finally, we investigate the future trends and provide practical techniques that could be used to fulfill the requirements for rapid analysis of food at a low cost.

Chitin/Ca solvent-based conductive and stretchable organohydrogel with anti-freezing and anti-drying.

Conductive hydrogel flexible sensors have attracted considerable research interest because of their good conductivity, flexibility, and biocompatibility. However, conventional hydrogels suffer from dehydration under ambient environments and freezing at low temperatures. Herein, we prepared a chitin/polyacrylamide organohydrogel with highly stretchable, anti-freezing, and anti-drying properties. This organohydrogel was creatively prepared by one-step radical polymerization in the chitin and calcium chloride/methanol (Ca solvent) aqueous solution. Benefiting from the chitin/Ca solvent system, the organohydrogel shows relatively high stretchability (improve ~5 times), excellent anti-freezing (up to -80 °C) upon long-term storage, and anti-drying (67 days under normal environment) performance. What's more, the reversible noncovalent bonds in the organohydrogel endow it with repeatable multi-purpose adhesion and rapid self-healing, while the abundant free ions grant it good conductivity to be a flexible sensor. Therefore, it is promising that this chitin-based conductive organohydrogel with multifunctionality would provide wide application scopes of flexible electronic devices.

Superhydrophilic three-dimensional porous spent coffee ground reduced palladium nanoparticles for efficient catalytic reduction.

The use of functional biodegradable wastes to treat environmental problems would create minimal extra burden to our environment. In this paper, we propose a sustainable and practical strategy to turn spent coffee ground (SCG) into a multifunctional palladium-loaded catalyst for water treatment instead of going into landfill as solid waste. Bleached delignified coffee ground (D-SCG) has a porous structure and a good capability to reduce Pd (II) to Pd (0). A large amount of nanocellulose is formed on the surface of SCG after bleaching by H2O2, which anchors and disperses the palladium nanoparticles (Pd NPs). The D-SCG loaded with Pd NPs (Pd-D-SCG) is superhydrophilic, which facilitates water transport and thus promotes efficient removal of organic pollutants dissolved in water. Pd-D-SCG exhibits excellent room temperature catalytic activity for the removal of 4-nitrophenol (4-NP) and methylene blue (MB) in water and shows good chemical stability and recyclability in water, with no obvious decrease even after five repeated cycles.

Paper-based analytical device for high-throughput monitoring tetracycline residue in milk.

A low-cost and portable paper-based analytical device has been developed for high throughput and on-site monitoring TC residue in milk through visualized colorimetric reaction. The filtration and concentration effect induced by the porous nature of paper contribute to strengthen the color intensity, leading to quantitative and sensitive detection of tetracycline reaching 1 ppm detection limit, with the linear range of 1-100 ppm both in water and milk samples. The applicability was demonstrated by detection of TC in 18 different types of real milk samples with good recovery ranging from 88% to 113%. Furthermore, the dynamic degradation behavior of tetracycline was monitored through the device. To the best of our knowledge, this is the first report of colorimetric detection of tetracycline in milk using the paper-based device. This simple, fast, cost-effective (~$0.50 per device) and equipment-free paper-based platform provides a promising tool for future application in food and environmental safety.

From brown to colored: Polylactic acid composite with micro/nano-structured white spent coffee grounds for three-dimensional printing.

Functional fillers in three-dimensional (3D) printing composite filaments offer an innovative way spent coffee grounds (SCGs) can be reused. However, the inherent brownness of SCGs places a limit on the color in which the composite filament and, consequently, the finished print appears. Herein, colored composite filaments for fused deposition modeling were successfully fabricated, where micro/nano-structured decolorized SCGs (MN-DSCGs) were embedded within polylactic acid (PLA) matrix. At the optimum condition, the 3D prints using composite filaments exhibit comparable tensile and flexural strength to the PLA counterparts. Also, they demonstrate superior melt flow and excellent print quality. Under the same condition, 3D printed MN-DSCGs/PLA blend has sufficient color restoration as compared to the prints using virgin PLA.

Nanochitin/metal ion dual reinforcement in synthetic polyacrylamide network-based nanocomposite hydrogels.

Nanocomposite hydrogels consisting of a synthetic matrix reinforced by nanosized crystalline polysaccharides offer significant potential in various fields. Different from nanocellulose, the combination of nanochitin with synthetic polymers to obtain nanocomposite hydrogels has not been extensively and systematically studied. Herein, a physically and chemically dual crosslinked nanocomposite hydrogel was successfully synthesized, where chitin nanowhiskers (ChNWs) and Zn2+ were incorporated within polyacrylamide (PAAm) matrix. Nanochitin/metal ion dual reinforcement imparts increased elasticity, enhanced mechanical properties, and improved recovery performance to PAAm network. The PAAm/ChNWs/Zn2+ hydrogel could be stretched to over 13 times its original length with tensile strength of 321.9 ±â€¯8.2 kPa, and restore its original shape rapidly even when compressed at a strain of 95% with a corresponding compressive strength of 6.95 ±â€¯0.20 MPa. The multiple crosslinks and interactions among ChNWs, Zn2+ and synthetic polymeric network were investigated. Moreover, the hydrogel was applied in drug release and soft bioelectronics.

Rapid preparation of highly transparent piezoresistive balls for optoelectronic devices.

We report a rapid fabrication strategy of highly transparent piezoresistive balls with excellent pressure-sensitivity and toughness by photopolymerization of polymerizable deep eutectic solvents. By careful design and integration, a number of optoelectronic devices have been constructed with the piezoresistive balls as building blocks.

High-strength paper enhanced by chitin nanowhiskers and its potential bioassay applications.

In this paper, nanochitin was used as an alternative natural nanomaterial to combine with cellulose fibers for fabricating high-strength paper. Two typical chitin nanowhiskers having contrasting sign of surface charge were compared to evaluate the enhancement performance on paper in details. The results show that nanochitin with positive charges on the surface has a significant effect on the strength properties of the prepared paper, especially on wet strength. When the dosage of chitin nanowhiskers was 2%, the wet strength index was increased to 2.48 N·m/g, which is important for paper-based analytical devices with the common use in liquid analysis. Typical colorimetric glucose assays were successfully performed, suggesting the improved analytical performance on these prepared paper.

Highly transparent, weakly hydrophilic and biodegradable cellulose film for flexible electroluminescent devices.

Developing green substrates based on cellulose to substitute synthetic plastics meet the requirement for the sustainable future. However, cellulose-based substrates supporting for building electronic devices are usually opaque and highly hydrophilic, which ultimately limits the performance of optoelectronic devices. Herein, we report a new avenue for fabrication of highly transparent, weakly hydrophilic and biodegradable cellulose film. The acquired cellulose film not only has high transparency (over 90%), but also displays weak hydrophilicity (∼79° of initial water-contact angle) and still remains 3.5 MPa of tensile strength after soaking for two days in deionized water. Additionally, the degradation half-life of cellulose film is 20 days, and the cellulose films also have better thermostability. Moreover, the flexible electroluminescent devices have been successfully constructed by using this cellulose film as a green substrate. This novel strategy will greatly enrich the applications of cellulose films for next generation green electronics.

Conductive biomass-based composite wires with cross-linked anionic nanocellulose and cationic nanochitin as scaffolds.

In this study, a series of conductive composite wires were successfully prepared by combining dispersions of multi-wall carbon nanotubes (MWCNTs) and TEMPO-oxidized cellulose nanofibers (TOCNFs) with different MWCNTs contents into a dispersion of partially deacetylated α-chitin nanofibers (α-DECHNs) followed with a drying process. The TOCNFs/MWCNTs/α-DECHNs composite wires were prepared by extruding the negatively charged TOCNFs/MWCNTs dispersion into the positively charged α-DECHNs dispersion. The contact of the positively charged α-DECHNs and the negatively charged TOCNFs/MWCNTs triggers the electrostatic interaction (heterocoagulation) resulting in wire-shaped conductive composites. The SEM analysis indicates this conductive composite material has a wire-like shape with a rough but tight surface. The properties of samples were characterized by a zeta potential analyzer (Zetasizer Nano), a four-probe, an electrochemical workstation, a Fourier transform infrared spectroscopy (FTIR), an X-ray diffractometer (XRD), and a thermogravimetric analyzer (TG). Besides, the conductivity and the AC impedance of TOCNFs/MWCNTs/α-DECHNs composite wires with different MWCNTs contents were also analyzed. The conductivity of the composite wire increases from 9.98 × 10-6 S∙cm-1 to 1.56 × 10-3 S∙cm-1 as the MWCNTs content raises from 3.0 wt% to 14.0 wt%. When the MWCNTs content reaches 14.0 wt%, the prepared composite wire can light up LED at a voltage of 5 V, indicating the great potential of this biomass-based conductive composite in conductive material application.

Highly Stretchable, Strain-Sensitive, and Ionic-Conductive Cellulose-Based Hydrogels for Wearable Sensors.

To extend the applications of natural polymer-based hydrogels to wearable sensors, it is both important and a great challenge to improve their mechanical and electrical performance. In this work, highly stretchable, strain-sensitive, and ionic-conductive cellulose-based hydrogels (CHs) were prepared by random copolymerization of allyl cellulose and acrylic acid. The acquired hydrogels exhibit high stretchability (~142% of tensile strain) and good transparency (~86% at 550 nm). In addition, the hydrogels not only demonstrate better sensitivity in a wide linear range (0%-100%) but also exhibit excellent repeatable and stable signals even after 1000 cycles. Notably, hydrogel-based wearable sensors were successfully constructed to detect human movements. Their reliability, sensitivity, and wide-range properties endow the CHs with great potential for application in various wearable sensors.

Portable paper sensors for the detection of heavy metals based on light transmission-improved quantification of colorimetric assays.

An accurate quantification method with a wide linearity range is paramount for the development of low-cost, portable and point-of-care sensors. This work reports a new approach to analyze the colorimetric assays on paper-based sensors using the quantification from a light transmission method. Compared to the commonly-developed color intensity measurement on scanned digital images, a portable transmission densitometer is capable of directly quantifying the optical density of colorimetric results. The detection of heavy metals in an aqueous system, including Fe(ii), Cu(ii), and Ni(ii), was carried out to demonstrate the good performance and reliability of this method. Our measurements show that the linear quantification range spans from 0.5-500 mg L-1 for the assays of Cu(ii) and Fe(ii) and from 2-500 mg L-1 for Ni(ii) based on the reading of transmitted light through the assay spot. As a comparison, the linear range is restricted to 0.5-50 mg L-1 for the same assays when analysed by the common reflection method, suggesting a significant improvement in the accuracy and sensitivity of high analyte concentrations from the light transmission method. By expanding the linearity range, this method further streamlines the sampling procedure during analysis and will greatly advance the future development of paper-based analytical sensors.

Fabrication of transparent and superhydrophobic nanopaper via coating hybrid SiO2/MWCNTs composite.

Nanopaper prepared from cellulose nanofibers (CNFs) is a kind of promising substrate for various high-tech devices. However, several drawbacks including poor water stability and weak corrosion resistance still remain, which limit the practical applications of the nanopaper. Herein, we present a simple and low-cost method for fabricating transparent and superhydrophobic nanopaper by spraying fluorinated silica/multi-walled carbon nanotubes (SiO2/MWCNTs) composite on the nanopaper. A series of functional nanopaper were fabricated, which shows excellent performance of water repellency, chemical stability, conductivity, thermostability and self-cleaning property. Among them, the nanopaper modified with the composite containing 0.5 wt% MWCNTs has a water contact angle of about 163°, transparency of 79.96% and the sheet resistance of 3.15 × 106 Ω sq-1. The combination of the promising features in a material offers attractive prospects, and enables our nanopaper could be tailored for emerging applications such as flexible electronics, display protection and intelligent packages.