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Paper-based devices are always more gaining a relevant position in the field of sensors. The continuous demand for affordable, simple, sustainable, and portable devices, is making paper as the ideal basis towards the realization of analytical tools for the easy self-testing. In this work, we demonstrate, for the first time, the development of a disposable paper-based printed electroanalytical strip for reliable, rapid, and high-throughput detection of glutathione in blood. The detection is based on the thiol-disulfide exchange reaction, which produces a detectable compound easily oxidizable at a Prussian Blue/carbon black nanocomposite involving a favorable low-interference overpotential. This nanocomposite is mixed within a carbon-based conductive ink and successively screen-printed onto a wax-patterned filter paper. The employment of paper provides a reagent-free device, as a consequence of the reagents pre-loading within the testing area. After the experimental conditions have been optimized, glutathione has been detected up to 10 mM, with a detection limit of 60 μM, and a sensitivity of (0.102 ± 0.005) μA/mM. This sensor showed satisfactory repeatability (relative standard deviation equal to 10%, for detection of glutathione 1 mM), especially by considering the hand-made manufacturing process. The “real-world” applicability of this strip has been evaluated by quantifying blood glutathione at physiological levels and by recovery studies achieving satisfactory values.

Graphical abstract, Highlights • Detection of cytokine storm biomarkers with mobile biosensors. • Immunosensors are made solely of cellulose modified with antibody-decorated nanoparticles. • Turnaround time under 10 min. • Detection of biomarkers in respiratory samples allows monitoring local inflammation. • Compatible with decentralized health care schemes., Decentralizing COVID-19 care reduces contagions and affords a better use of hospital resources. We introduce biosensors aimed at detecting severe cases of COVID-19 in decentralized healthcare settings. They consist of a paper immunosensor interfaced with a smartphone. The immunosensors have been designed to generate intense colorimetric signals when the sample contains ultralow concentrations of IL-6, which has been proposed as a prognosis biomarker of COVID-19. This is achieved by combining a paper-based signal amplification mechanism with polymer-filled reservoirs for dispensing antibody-decorated nanoparticles and a bespoken app for color quantification. With this design we achieved a low limit of detection (LOD) of 10−3 pg mL-1 and semi-quantitative measurements in a wide dynamic range between 10−3 and 102 pg mL-1 in PBS. The assay time is under 10 min. The low LOD allowed us to dilute blood samples and detect IL-6 with an LOD of 1.3 pg mL-1 and a dynamic range up to 102 pg mL-1. Following this protocol, we were able to stratify COVID-19 patients according to different blood levels of IL-6. We also report on the detection of IL-6 in respiratory samples (bronchial aspirate, BAS) from COVID-19 patients. The test could be easily adapted to detect other cytokines such as TNF-α and IL-8 by changing the antibodies decorating the nanoparticles accordingly. The ability of detecting cytokines in blood and respiratory samples paves the way for monitoring local inflammation in the lungs as well as systemic inflammation levels in the body.

In this study, fabrication of microfluidic paper based analytical devices (μPADs) by microembossing was proposed. Different from the embossing methods described in the literature, the filter paper was embossed such that a protruded structure was formed, which subsequently became the channel after heating the wax at the backside of the filter paper. It was found that, when using the Whatman No. 3 filter paper, the embossing pressure needed to be larger than 50 kg/cm2 in conjunction with using a minimal 2-mm wide channel, and the wax heating time ranged from 15 to 45 s in order to obtain a reliable μPAD with repetitive and consistent results. In addition, there was no need of a hydrophobic material as the backside support. The glucose detection was demonstrated using the μPADs as fabricated and a linear relationship was obtained between 5 and 50 mM glucose concentrations. With the proposed method, the processing time of fabricating μPADs can be reduced within approximately 1 min.

The paper drying process has the highest level of energy consumption in the pulp and paper production process. Analysis and optimization of the energy system during the paper drying process is critical for improving the energy efficiency of the entire paper mill. In the existing model for the paper drying process, the solution requires accurate boundary conditions such as the air temperature and humidity of the pocket area and the cylinder surface temperature, which are very difficult to obtain in the papermaking process. This can result in significant deviations between the model solution and the actual production process. This paper focuses on the single-tier dryer cylinder-based paper drying process that has been widely used with high-speed papermaking machines in recent years. A mathematical model is proposed based on real-time data. The verification via industrial production demonstrates that the proposed model is reliable for the paper drying process. Based on the simulation results, two optimization operations have been proposed. The energy consumption decreases from 1.51 t steam/t paper to 1.44 t steam/t paper, 4.6% of the steam and 1.26 × 106 RMB can be saved for a medium-scale paper mill with the annual production capacity of 105 t paper.

L -dopa is a chiral drug that has been extensively used for the treatment of Parkinson’s disease. The concentration of L -dopa plays a vital role in the treatment, and this work emphasizes on designing a versatile platform for the quantitative and selective detection of L -dopa using reduced graphene quantum dot (rGQD). The platform is efficient in three different sensing methods, viz. fluorescence turn-on, filter paper-based sensing, and electronic measurements. The rGQD undergoes a dramatic fluorescence turn-on in the presence of L -dopa in aqueous media and artificial urine with a detection limit as low as 1.307 µM and 1.217 µM respectively. Experimental evidence revealed that the fluorescence enhancement is attributed to aggregation-induced emission mechanism. The system is also applicable for visual detection of L -dopa using filter paper strips treated with rGQD and develops bright fluorescence under ultra-violet irradiation. Apart from this, electrical sensors for L -dopa were also developed by preparing rGQD treated poly-vinyl alcohol films, and the increase in the current conduction with varying concentrations of L -dopa was observed. The films produce 2.5 order higher current conduction at 300 μM of L -dopa with a detection limit of about 13.136 µM. At the final stage, we have designed flexible electronic devices using these materials that develop 1.3 order higher current for L -dopa. The devices exhibit excellent air stability under varied relative humidity conditions as well as high bending stability for potential practical applications.

A novel visual and fluorometric-sensor paper is prepared for the monitoring of atmospheric humidity and ethanol. The paper contains a combination of copper nanoclusters (CuNCs) and carbon dots (CDs), immobilized on a filter paper. This makes it a dual-emission system. The visual sensor shows bright fluorescence and has a diameter of ∼8 cm with uniform and homogeneous surface. The detection mechanism of the sensing paper is based on the fluorescence intensity variation of CuNCs in different environments. Desirable linear relationship is observed between fluorescence intensity ratio (red/blue) and humidity. Visible color transformation of this sensor paper is observed in the humidity range ∼40-80%, implying utility for easy and facile atmospheric humidity determination. Furthermore, due to the water and ethanol have different impacts on the spectrum, this paper-based fluorescent probe shows excellent response to ethanol. Therefore dual-emitting sensing paper, when suitably calibrated, shows promise for visual and fluorometric sensing platforms aimed at humidity or ethanol detection.

Signal amplification in colorimetric biosensors usually requires labile reagents and/or additional steps, which are not ideal for in-field measurements. Here we show that the limit of detection of a gold nanoparticle-labeled colorimetric immunosensor can be decreased 10-fold by performing the assay on a folded piece of paper. In this approach, the intrinsic porosity of the substrate enables generating multiple signals with a single drop of reagent. This yields combined signals with higher optical density thanks to the semitransparent nature of the wet material. It will be shown that this method can decrease the limit of detection 10 times in a model immunosensor for the detection of immunoglobulins. The procedure is so straightforward that it could be easily implemented to decrease the limit of detection of microfluidic paper-based analytical devices with colorimetric readouts.

The Swedish pulp and paper industry (PPI) must increase energy efficiency to remain competitive on the global market, which has experienced entries from countries with cheaper energy and raw material supplies. Interactions among variables for energy use, production, energy management, electricity price and firm characteristics (FC), in different types of mills, i.e., pulp, paper and integrated mills, in Sweden from 2006 to 2015 indicate that correlations among the studied variables were different in different types of mills. This difference between types of mills seemed to originate partly from varying accessibility to production residue that could be used for energy. For all types of mills, variation of electricity prices did not correlate significantly with energy efficiency during the study period. The studied FC were firm's age, number of employees, number of companies in company group, net sales and profit for the year. Energy efficiency was more affected by the variables characterizing energy and production compared to the variables representing FC. This study also suggested presence of possible discrepancies between FC that were perceived as barriers to energy management towards energy efficiency, according to previous studies, and what was shown by the data combining variables representing energy use, production and FC.

One of the benefits of Internet of Vehicles (IoV) is improved traffic safety and efficiency, for example due to the capability to share vehicular messages in real-time. While most of the vehicular messages only need to be shared by nearby vehicles, some messages (e.g., announcement messages) may need to be more broadly distributed, for example to vehicles in a wider region. Finding a single trusted entity to store and distribute such messages can be challenging, and vehicles may not be inclined to participate (e.g., generation and distribution of announcement messages) unless they can benefit from such participation. In addition, achieving both security and privacy can be challenging. In this paper, we propose a blockchain based secure data sharing system to address the above challenges in an IoV setting. Specifically, in our system, announcement messages are stored using blockchain. To encourage/incentivize participation, vehicles that faithfully broadcast the announcement messages and/or contribute to the block generation will be rewarded by some cryptocurrency. Our system is also designed to be privacy-preserving and realizes both priori and posteriori countermeasures.

Valorisation involves conversion of toxic compounds into value added products. The present study has tried to evaluate the potential of vermicomposting in management of different types of toxic paper mill wastes such as primary waste (VCP) and secondary waste (VCS) using Eisenia fetida for 60 days. The procedure was performed using sundried samples of paper mill wastes, cow dung and straw in different trial sets using different ratios. The study had revealed that the trial sets (VCP1 and VCS1) using ratio of paper mill waste: Cow dung: Straw (5:4:1) were effective in maintaining physiochemical parameters and different population attributes of earthworm. The present study had also demonstrated the enzymatic enrichment of vermicompost in terms of 19 enzymes such as α-Glucosidase, lipase, leucine aminopeptidase etc. in maintenance of C/N ratio of the compost. A significant reduction of heavy metals were noticed in vermicomposting of primary waste (VCP1) as Zn (40%) ​> ​Pb (36%) ​> ​Cr (28%) ​> ​Cu (25%) and secondary waste (VCS1) as Zn (44%) ​> ​Pb (41%) ​> ​Cu (19%) ​> ​Cr (13%). Such reduction of heavy metal was highly correlated with the reduction of C/N ratio of the vermicompost. The process of bioremediation was further manifested through the regular monitoring of bioaccumulation factor (BAF) among earthworm population in vermicomposting of primary waste (VCP1) as Zn (0.40) ​> ​Cu (0.23) ​> ​Cr (0.18) ​> ​Pb (0.11) and secondary waste (VCS1) as Zn (0.47) ​> ​Cu (0.25) ​> ​Cr (0.21) ​> ​Pb (0.14). Therefore, the study concludes that the ratio of paper mill waste, cow dung and straw (5:4:1) can be an efficient formulation in qualitative enrichment of different toxic organic paper mill wastes through vermicomposting.

Recently, triboelectric nanogenerator (TENG) has aroused considerable interest due to various advantages. Particularly, one benefit which sand out is that the triboelectric pair of TENG is very tolerant to the material composition. Thus, it is possible and significant to develop cost-effective TENG using commercial and inexpensive material. In this work, we present a paper TENG by repeated folding completely using commercially available commodity materials, such as paper, brush pen, Teflon tape, and conductive ink. Paper is used as functionally triboelectric pair and spring-like supporting structure. The stacked paper TENG is fabricated and large enhancement of output performance is observed. The generated electric outputs have been used to directly light-up commercial LEDs. The proposed TENG has demonstrated simplicity and cost-effective, which is suitable for flexible electronics.

A series of dye-sensitized solar cells have been constructed using titania-rich paper industry waste materials. The cells obtained were able to produce solar electricity, but with relatively poor photon-to-current efficiencies reaching only 0.47% and short circuit photocurrent densities up to 1.14 mA × cm−2, but reasonable fill factors and very good open circuit photovoltage reaching 67% and 719 mV, respectively. The titania-rich waste samples were prepared by removal of water and post-production organic residues and well characterized with XRD, XRF, FT-IR, SEM, TEM, EDS and UV–vis techniques. This paper presents an alternative solution for green energy production and conversion of pollutants to useful materials.

When portability, low cost, and green energy requirements are considered, the search for an electricity generator harvesting environmental energy based on available cheap commercial materials and simple fabrication techniques becomes significantly important. In this study, the capability of ultrasoft and cuttable paper-based triboelectric nanogenerator (P-TENG) to harvest mechanical energy is demonstrated. The P-TENG maintains the excellent softness of tissue paper and has the characteristics of light weight (~ 87 g/m2), high electric conductivity (6 Ω/square), and low cost (~ $3.00/m2). More importantly, the P-TENG can be cut by the end-user to modify its size and shape and still function properly. The mechanical energies available during cleaning processes, the energy associated with the body's motion, sound energy, and wind energy can be directly harvested by using the P-TENG. The high portability of the P-TENG, the simple and scalable fabrication processes, low cost, and its ability to harvest mechanical energy make the P-TENG important for the development of green, portable, energy-harvesting devices.

Hydrophobic properties belong to the most important factors which determine functional properties of paper products. A number of methods related to the measurement of the interaction between water and paper are already used but most of them give results after specific period of time whereas many unit operations in modern industrial processes (e.g. printing) last usually less than one second. As a result, most of the existing methods are not corresponding to today’s requirements. The aim of the presented research was to develop the method based on image analysis for measuring the dynamics of penetration and permeation of liquid through paper. Special device named eXtended Liquid Penetration Analyser (XLPA) was built for this purpose. Based on the obtained results, the method developed allows to observe and analyse the dynamics of liquid permeation through paper. The proposed method fully replaces the method implemented in the PLG Sizing Tester, which estimated the time of a 50% decrease in brightness of a tested paper sample permeated by ink. Presented method offers the possibility of quantitative measurement of changes in liquid absorption with time resolution of 1/60 s. At the same time, thanks to the use of a camera and image analysis, it is possible to detect local areas of non-homogeneity in paper structure that differ with regards to their capability to absorb liquid, as well as to determine quantitative measures that characterize the non-homogeneity of the permeation process with reference to paper surface.

Electrochemiluminescence (ECL) is a powerful technique with the advantages of high sensitivity and a wide dynamic range. However, most of previous strategies based on ECL could only detect one analyte so that it is inevitable to investigate the selectivity and influences of interferences. Herein ECL integrated with paper chromatography was showed to be a potential platform for separation and detection of two environmental hormones (bisphenol A, BPA, and dibutyl phthalate, DBP). In our approach, carbon conductive tape was attached to an ITO glass and then modified with multi-walled carbon nanotubes (MWCNTs) and CdSe quantum dot (CdSe QDs) to fabricate the working electrodes for ECL detection. The synthesis of CdSe QDs was optimized based on their photoluminescence spectra and the ECL intensities. The modified electrode was then coupled in the paper-based analytical devices consisting of the filter paper modified with chitosan. Based on their quenching effect on the ECL emission of CdSe QDs, excellent linear relationships could be obtained between decreased ECL intensities and both the concentrations of DBP and BPA. Besides, DBP and BPA could be separated based on their retention time by tilting the filter paper for 30° and then detected with ECL. This study suggested that paper-based analytical devices could be potentially applied for separation and detection of multiple targets due to their ease of fabrication and convenient operation.

Herein, we report the development of a portable, iPhone controlled, and inexpensive infrared lightbox for improving the detection limits of paper-based phosphate devices. Commercial devices utilize the molybdenum blue protocol for phosphate detection. Although these devices are user-friendly and have a long shelf life, their standard mode of operation suffers from low sensitivity since it gives semi-quantitative results by comparing to a color chart. To improve the results, we constructed a compact infrared lightbox that communicates wirelessly with a smartphone equipped with a developed colorimetric analyzer. This system measures the absorbance of radiation for the molybdenum blue reaction in the infrared region of the spectrum. By using the infrared lightbox, the detection limits for two popular paper-based commercial devices were improved by a factor of 4 for the Quantofix devices and a factor of 6 for the Indigo units with repeatability of less than or equal to 1.2% RSD.

With “drop-slip” (DS) bulk liquid flow on a fully inkjet-printed microfluidic paper-based analytical device (μPAD), a new method for the rapid transport of sample liquid is presented. The main driving force for DS flow is the slip flow of fluid on wetted porous cellulose acting as a lubricated surface, which is predominantly influenced by the width of the hydrophilic channel and the surface tension of the sample liquid. The application of DS flow is demonstrated by a model colorimetric metal assay (Zn2+, Cu2+, Fe2+) with inkjet-deposited indicators on a μPAD with optimized channel dimensions of 2 mm width and 110 μm height. The presence of bulk liquid on the entire device does not result in any mixing of assay components across adjacent sensing regions connected by microfluidic channels. DS flow is a useful alternative sample liquid transport method for μPADs, allowing to perform multiple fully independent assays with enlarged sample volumes without requiring any significant variation in device design and fabrication.

Porcine pseudorabies is one of the most serious infectious diseases influencing the pig-breeding industry. It inflicts enormous losses, underscoring the urgent need for the development of a clinical method for accurate and quick diagnosis of wild-type PRV infection. PRV-gE antibodies are an excellent indicator of PRV source, as their presence in the serum of individuals infected by wild-type PRV but not in those administered PRV gE-deleted vaccines enables distinction of wild-type PRV infection from vaccine immunization. For this study, we developed a miniaturized paper-based smartphone biosensor detection system (paper-biosensor) based on a blocking immunoassay for differential diagnosis of wild-type pseudorabies virus infection versus vaccination immunization. Latex beads (LBs) were used to label PRV, and the test line (T-line) was coated with PRV gE-mAb. The ambient light sensor of the smartphone was used to measure the transmitted light intensity from the T-line. Under optimized conditions, the paper-based smartphone biosensor achieved excellent sensitivity and selectivity. In tests of swine clinical samples (n = 101), the agreement between this method and the most widely used commercial gE-ELISA kit was 98%. Moreover, our method was rapid (15 min), low cost, and easy to operate, endowing it with great promise as an on-site differential diagnosis tool for PRV infection.

In this paper an original and exhaustive mathematical modelling of air impingement drying systems for the production of tissue paper in the Yankee-hoods configurations is reported, which offers the possibility to optimize its energy performance. The model takes into account many detailed operative parameters of the overall drying process with the aim to execute its energy and mass balance and to evaluate its energy performances. The validity of the mathematical model has been assessed by comparison with actual data from an existing tissue paper mill. Finally, the energy performances of two different layouts of the air system have been evaluated and compared. Changing the operative parameters of the drying process, such as air jet temperature and speed and moisture content of the extraction air, it is possible to obtain the same paper production with an energy saving of about 4.5%. In average, the layout with two parallel air circuits assure an energy saving of about 1% with respect to the layout with a single air circuit.

In order to explore hydrothermal carbonization (HTC) behavior of municipal solid wastes (MSW), four typical components, waste textile, wood, paper and food, were employed to perform HTC and co-HTC process. The experiments were conducted at 240 ○C and 90 min with a 1:12 solid/liquid ratio, where blending ratios of 1:3, 1:1 and 3:1 with waste textile were investigated. As expected, the increase of fixed carbon and carbon content improved the fuel potential of hydrochar. The synergistic index (SI) analysis clearly indicated that significant synergistic effects occurred during co-HTC process. Specifically, all the SI values of hydrochar yield from co-HTC of waste textile with wood and paper were negative, while all SI values of hydrochar yield for waste textile with food were positive. Particularly, the SI values of fuel ratio for all hydrochars were positive which suggested co-HTC could promote to enhance the coalification degree of hydrochars. However, the undesirable increment of O content for hydrochars (derived from 75%waste textile-25% waste food and 50%waste textile-50% waste food) decreased the high heating value. The combustion behavior and nth-order kinetic model analysis showed that hydrochars derived from co-HTC rendered a more stable and lasting combustion profile.

During the folding process substrates are exposed to high-localized stresses, which in the case of coated papers and boards, can lead to decreased aesthetic features or complete loss of functionality. Production efficiency of the folding process could be improved by an automated, computer vision-based inspection system. For such a task, different existing computer-aided fold-crack evaluation approaches were analyzed. A detailed research was conducted to propose an image processing based fold cracking assessment via finding optimal sample preparation and digitization techniques and developing an algorithm for the digital image analysis and feature extraction. The analysis of the applicability of different sample preparation and digitization parameters, as well as the proposed digital image feature, was done by correlation evaluation, one-way analysis of variance (ANOVA) and corresponding post hoc tests. The results indicated that the developed algorithm fulfils the set requirements and the proposed feature of digitized samples faithfully describes the analyzed fold-cracks.

This paper describes for the first time the use of a 3D pen to fabricate paper-based analytical devices. 3D pens are usually commercialized as “toy for children” and a kit containing four units and a handheld flashlight can be found at cost of US$ 10−15. The protocol involves the 3D pen drawing of the desirable layout on paper using an acrylic resin followed by a curing stage through a handheld flashlight. The barriers created with 3D pen revealed good chemical resistance when exposed to acid and alkaline solutions, surfactants and organic solvents, except ethanol. The proposed approach enabled the creation of zones with 2 mm diameter and channels with 3 mm wide. The analytical feasibility of the devices created with 3D pen was investigated through colorimetric measurements of clinically and environmentally relevant analytes using a free application for image capture and analysis. Considering the instrumental simplicity and the satisfactory analytical performance, we believe the reported approach exhibits potentiality to be implemented in laboratories or research centers with limited resources, opening possibilities to create the desirable devices for the point-of-need applications using only a pen and a flashlight.

The phenomenon of periodic self-imaging of optical beams, occurring inside any graded-index (GRIN) medium, was studied during the decade of the 1970s and was exploited to commercialize the GRIN lens. It has been found in recent years that the periodic self-imaging also affects the nonlinear propagation of optical pulses inside multimode GRIN fibers. In this paper, we first present the theory of self-imaging in linear GRIN fibers using a modal expansion approach. It is shown that the optical field at any point inside the fiber can be written without any reference to the fiber modes as a two-dimensional integration over the input field using a propagation kernel that is similar to that found in diffraction theory. However, this kernel has a specific property that reproduces the input field precisely in a periodic fashion along the length of a GRIN fiber (self-imaging). We apply this kernel to study the propagation of a Gaussian beam and discuss how self-imaging is modified by self-focusing produced by the Kerr nonlinearity. We then consider propagation of the continuous and pulsed Gaussian beams inside a GRIN fiber and discuss how self-imaging affects the modulation instability, leads to the formation of GRIN solitons, and produces novel temporal and spectral features when short optical pulses are launched that are intense enough to form high-order solitons.

The waste biomass has immense opportunities and plenty of potentials to be an efficient source of renewable energy. Initially, native unripe coconut husk (NCH) was used as raw material for fluidized bed gasification. Then NCH was treated with paper and pulp waste water to impregnate metals present in it for getting enhanced H2 yield in fuel gas. Humidified air was used as gasifying medium, which served the purpose of introducing water vapour to take part in the gasification process. Then after, gasification medium was retrofitted with CO2, which enhanced both the higher heating value (HHV), and CO and H2 content in the fuel gas. This research serves the dual benefit of energy generation and waste minimization. HHV of unripe coconut husk was investigated and found to be 20.95 MJ/kg. H2 yield and HHV from impregnated coconut husk (ICH) were obtained as 55.55 vol % and 5.24 MJ/Nm3, respectively at HER 0.1 and gasification temperature of 850 °C in case of fluidized bed gasification. The GC-MS analysis of fuel oil obtained from ICH gasification was done to get the information about high yield of fuel gas as promise product of fluidized bed gasification.

Production of transportation fuels from biorefineries via biomass gasification has been suggested as a way of introducing renewable alternatives in the transportation system with an aim to reduce greenhouse gas emissions to the atmosphere. By co-locating gasification-based processes within heat demanding industries, excess heat from the gasification process can replace fossil or renewable fuels. The objective of this study was to compare the heat integration potential of four different gasification-based biorefinery concepts with a chemical pulp and paper mill. The results showed that the choice of end product which was either methanol, Fischer-Tropsch crude, synthetic natural gas or electricity, can have significant impact on the heat integration potential with a pulp and paper mill and that the heat saving measures implemented in the mill in connection to integration of a gasification process can increase the biomass resource efficiency by up to 3%-points. Heat saving measures can reduce the necessary biomass input to the biorefinery by 50% if the sizing constraint is to replace the bark boiler with excess heat from the biorefinery. A large integrated gasification process with excess steam utilisation in a condensing turbine was beneficial only if grid electricity is produced at below 30% electrical efficiency.

This paper presents a comparison between four gasification-based biorefineries integrated with a pulp and paper mill. It is a continuation of 'Transportation fuel production from gasified biomass integrated with a pulp and paper mill - Part A: Heat integration and system performance'. Synthesis into methanol, Fischer-Tropsch crude or synthetic natural gas, or electricity generation in a gas turbine combined cycle, were evaluated. The concepts were assessed in terms of GHG (greenhouse gas) emissions and economic performance. Net annual profits were positive for all biofuel cases for an annuity factor of 0.1 in the year 2030; however, the results are sensitive to biofuel selling prices and CO2,eq charge. Additionally, GHG emissions from grid electricity are highly influential on the results since all biofuel processes require external power. Credits for stored CO2 might be necessary for processes to be competitive, i.e. storage of separated CO2 from the syngas conditioning has an important role to play. Without CO2 storage, the gas turbine case is better than, or equal to, biofuels regarding GHG emissions. Efficiency measures at the host mill prior to heat integration of a gasification process are beneficial from the perspective of GHG emissions, while having a negative impact on the economy.

Paper mill sludge (PMS) can be efficiently utilized to produce fuels and chemicals. However, wastewater is usually generated during the de-ashing step of the PMS for fibrous materials recovery. Per process requirements, the wastewater stream must be treated which results in an increase in the overall process production cost. Therefore, this research aims at reusing the wastewater produced during the de-ashing step as a substitute for freshwater addition during the conversion of PMS into ethanol. The advantages of this approach include reducing the amount of wastewater produced and enhancing the overall efficiency of the process. It will contribute to the circular economy of zero waste discharges. The results showed that 30% of the process wastewater can be recycled without affecting the enzymatic hydrolysis and ethanol fermentation. Hence, the amount of wastewater that needs to be treated is reduced by 30% resulting in a cost reduction of 22.5%. The results also showed that wastewater recycling minimized the energy demands in the distillation and evaporation units by 1206 kJ/kg. The energy reduction is due to the increase of metals and total soluble solids in the broth stream after fermentation. This process configuration enhanced the process economy, saved energy and managed waste streams.

In this study, through orthogonal experiments design, the influences of ultrasonic pretreatment (frequency, power and treatment time) on co-pyrolysis and catalytic pyrolysis of municipal solid waste and paper mill sludge were explored. The differential thermogravimetry curves became steeper and the peak values were larger after pretreatment, which made the pyrolysis reaction rapidly and the volatile separated out timely. However, the change of pyrolysis characteristics was not obvious after adding MgO. The catalytic effect of MgO increased with the increase of sludge ratio. After pretreatment, the average activation energy of the samples had an overall increasing trend, but the change was small. MgO had a decreasing effect on activation energy, and with the increasing proportion of sludge the degree of reduction became significant. In addition, high ultrasonic frequency had a negative effect on reducing activation energy.

Single-electrode mode triboelectric nanogenerator (TENG), as an emerging and efficient sustainable power source, is highly sought to develop a low-cost fabrication process for the mass production at the commercial level. In this paper, we report an easy protocol for the fabrication of graphite coated paper (GCP) based electrode along with its application in highly flexible single electrode mode TENG for converting waste environmental energy to electricity. This GCP exhibits an excellent flexibility and hydrophobicity with sheet resistance of ~1.5 kΩ sq−1. GCP-TENG is made up of polytetrafluoroethylene film tape, as the triboelectric layer, and GCP, as the conductive single electrode as well as its roll to roll fabrication was demonstrated. By efficiently harvesting hand tapping energy, GCP-TENG can generate a maximum open-circuit voltage up to ~320 V and a maximum short-circuit current density of ~0.8 μA cm−2, sufficient for charging capacitors and power Light-emitting diodes (LEDs) and Liquid crystal displays (LCDs) with rectifying circuits. We also demonstrated that GCP-TENG can efficiently work when adjoined with the skin of Pig leading to an effective harvesting of energy from the physical motion of animal. To indicate the universal usage of GCP-TENG, a wide range of common materials, such as paper, polyethylene terephthalate (PET), wood, polymethyl methacrylate (PMMA) and fabrics like cotton and nylon, concluded in effective electrical outputs when contacted with GCP-TENG. The widespread mechanical energy in nature associated with wind and water energy can be directly harvested by GCP-TENG, thus, it can be a promising sustainable tool for obtaining waste environmental energy from our daily activities, e.g., skin-touch actuated electronics, wearable/patchable self-powered sensory system, etc.

Under the dual pressure of energy consumption and environmental pollution, mankind hopes to develop clean and renewable alternative energy, and the rapid development of fuel cells meets people's demand for energy-efficient power systems. The emergence of portable micro energy systems represented by microfluidic fuel cells, such as paper-based microfluidic fuel cells, has greatly enriched the means of medical detection to better cope with the threat of disease transmission. In this work, the numerical simulation method is innovatively introduced to study the paper-based microfluidic fuel cells. Both transient and steady-state modes are employed to demonstrate the whole operation process of the paper-based microfluidic fuel cell. In addition, the different structural parameters, including electrode spacing, the distance between electrode and inlet, channel thickness, and electrode length, are also investigated their influence mechanisms on cell performance. Results show that the increase of most structural parameters decreases cell output power in different degrees. Even on the premise that increasing channel thickness has a positive impact on the output power, the fuel utilization still shows a downward trend. These conclusions provide theoretical support and reference for future optimization work and accelerate the development of microfluidic fuel cells.

The generated gas bubbles in microfluidic fuel cells (MFCs) cover the active surface area of the electrode and greatly limit the cell performance. In this study, a feasible approach is proposed to effectively accelerate bubbles removal and enhance cell performance by embedding a paper separator in the middle of the microchannel. Visualization of bubble behaviors and the corresponding electrochemical measurements are performed to investigate the effect of bubbles on the cell performance. Periodical process of the bubble growth and removal leads to the fluctuation in the current density of the MFC. The rapid gas removal and the low ohmic resistance are observed after embedding a layer of filter paper in the microchannel, causing improved fuel transfer and smaller ohmic loss. Although the current density fluctuates more frequently, the fluctuation amplitude decreases and the cell performance is enhanced. Compared with the MFC without paper separator, the maximum power density and the limiting current density of the MFC with paper separator is increased by 25.2% and 130%, respectively. Moreover, the cell performance is improved with increasing the flow rate of reactant solution and the peak power density achieves 25.9 mW cm−2 under flow rate of 1500 μL min−1.

Utilizing the kinetic energy of a flowing river for irrigation could be tracked back to Hellenistic and Roman periods. In modern days, hydroelectric plants are built for harvesting the kinetic energy of the flowing river. However, a large investment is required in the hydroelectric plants for maximizing the power output. Here we present a low-cost and scalable TENG (triboelectric nanogenerators) based energy harvesting water wheel (ww-TENG). The water wheel works in a sliding freestanding TENG mode which generates power from the charges flow induced by contact electrification and electrostatic induction. A conformal fluorine coated carbon paper (f-CP) was employed to form the alternate electrodes. The deposited fluorine layer provides the benefits of high affinity to attract electrons as well as hydrophobicity for water repelling. The carbon paper offers a high electrical conductivity and rough structure to form a superhydrophobic property. These features enables a large charge induction and fast water/TENG separation for maximizing the power output of the energy harvesting water wheel. A lab-scale water wheel (diameter 10 cm and width 2.5 cm) is fabricated and a maximum 5.3 μW output power was measured under 50 MΩ resistance at a linear flow velocity of 2.6 m/s. The ww-TENG was employed for charging a 10 μF capacitor to 16 V and lighting up a commercial LED light bulb. As a comparison, an electromagnetic generator (EMG) could only charge the capacitor to 2.7 V with the same period of time. The EMG obtains a high power output at low load resistance case ( 10 MΩ). The present ww-TENG shows great potential for harvesting the kinetic energy from flowing river and targets for the applications with large load resistance like electrostatic systems.

Development of low-voltage driven multifunctional thermal igniters for nanoscale energetic materials (nEMs) is important for extending the application of nEMs to various thermal engineering fields. In this study, highly flexible heater chips capable of generating a sufficient amount of heat to ignite nEMs at a low voltage are demonstrated by incorporating a patterned aluminum-doped paper (AP) with polymeric substrates. A combination of automatic paper cutting and single-step ultraviolet polymer curing techniques helps in the fabrication of various designs of flexible AP heater chips in a simple and low-cost manner. Based on the AP heater chips, three models of flexible thermal igniters are designed to develop new functions such as selective ignition and sequential ignition in a single chip and successfully operated at low voltages. Two types of compact ignition systems are fabricated by fully integrating the arrayed AP igniters, circuit modules, and portable batteries in a three-dimensional printed single package and on a flexible circuit board. The systems are successfully demonstrated to ignite nEMs wirelessly and selectively with a smartphone.

Double-sided electrohydrodynamic jet printing of circuitry using silver nanowires (AgNWs) and dispensing of high viscosity silver nanoparticles (AgNPs) is demonstrated for the first time in the fabrication of a two-dimensional array of electrodes (3D circuitry) on a single sheet of paper. The penetration of AgNW ink through the paper’s thickness by capillary imbibition allows for multilayer electrical access to connect the individual electrodes. This makes it an automated and efficient choice as the functional area of the device is conserved and the surface of the paper is preserved. This allows for two-dimensional droplet manipulation on a paper-based digital microfluidics (PBDMF) platform. Compared to printed circuit board technology, paper-based electronics offer a range of desirable properties: they are light weight, portable, economical, flexible, biodegradable, and the materials are abundantly available. The fabricated PBDMF chip is demonstrated to be a low-cost, fully reconfigurable, and disposable point-of-care diagnostic platform for the environmental sensing of pesticide using organophosphorus hydrolase enzyme through colorimetric detection via smartphone.

This work demonstrates an innovative Al-air battery made of paper, which can inhibit Al corrosion, simplify battery system and reduce electrolyte storage. One major advantage of it is its minimum cost of fabrication. The corrosion inhibition effect originates from the high porosity and tortuosity of paper, which restricts the diffusive transport of hydroxyl ions to the Al surface. In this manner, low-grade Al can be directly utilized. Targeted for different application fields, three battery subtypes are proposed. The mechanically-rechargeable battery can be used repeatedly by refreshing its Al anode, providing relatively high power for charging portable electronics. The flexible battery employs embedded Al inside paper as anode and oxygen reduction ink as cathode, which is suitable for various single-use and flexible devices. Lastly, a printable battery is proposed by developing a successful Al ink for anode fabrication. Combined with existing printing techniques, this design may lead to a much smarter and more economic battery application in the future.

We describe a low cost optical temperature sensor that is simple to manufacture. The sensor is constructed by simple soaking of paper in a solution of the temperature sensitive luminescent indicator Ru(phen) 3 and subsequent lamination of the dried paper. Lamination prevents O 2 diffusion to the indicator and thus eliminates O 2 cross-sensitivity. The temperature sensitivity was up to −2% change in luminescence lifetime per K, a t 90 response time of 10 s. Besides luminescence lifetime based measurements, the sensor is well suited for ratiometric imaging with simple RGB cameras, where the temperature dependent red luminescence can be referenced by the blue luminescence of the optical brightener in the paper.

In the present era of the Internet of Things (IoT) and sensor networks, clean and sustainable power sources are in huge demand, and triboelectric nanogenerators (TENGs) are a hot cake in green energy production. Here, we have developed a contact-separation mode TENG using liquid-phase exfoliated 2D-hexagonal boron nitride nanosheets (BNNSs) coated on biaxially-oriented polyethylene terephthalate (BoPET) and paper as counter triboelectric materials, which showed an impressive 70 times higher power output than simple BoPET-paper TENG assembly. Even under a moderate finger tapping force (~3 N), the developed BNNSs/BoPET-paper TENG device could generate an open circuit output voltage of ~200 V and a short circuit current density of ∼0.48 mA/m2. While under load testing, the peak value of electric power density for the BNNSs/BoPET-paper TENG device reached ~0.14 W/m2 at 200 MΩ resistive load. The incorporation of BNNSs has significantly enhanced the electron-accepting capabilities of the BoPET film which is evident from the enhanced dielectric permittivity of the BNNSs/BoPET assembly, and thus resulted in the enhanced electrical output of TENG. Additionally, the fabricated BNNSs-TENG was successfully demonstrated for powering electronic gadgets such as LCD clock, digital thermometer, and LEDs through cyclic finger tapping force.

With the rapid development of flexible electronics, new opportunities are opening up for paper-based electrodes. Herein, an integrated paper electrode consisting of homogeneously mixed cellulose fibers, activated carbon (AC), and carbon black is fabricated using cotton stalks as the raw material. Assembled from two such electrodes, the flexible supercapacitor exhibits high energy density, high power density, and outstanding cyclability. Remarkably, the thickness and AC mass loading of the paper electrode can be easily scaled up to commercial levels (610 µm and 9.8 mg cm−2), while still delivering great performances. Moreover, it is demonstrated that the replacement of AC with Ni-Co layered double hydroxide or Fe2O3 can result in paper-based asymmetric supercapacitor with extremely high energy density (331 μW h cm−2 and 10.3 mW h cm−3), substantially outperforming conventional paper-based supercapacitors. The fabrication methodology of integrated paper electrodes in this report manifests great potential, offering a new vision for flexible energy storage.

This work presents the development and optimization of a very low cost, miniaturized and lightweight aluminum/silver oxide (Al/AgO) primary battery. The system is implemented on painted paper supported electrodes and it is activated using a small amount of water. The anode contains an improved composite based on aluminum powder. The cathode is made using an electrical conductive silver epoxy ink. The device displays a paper-based core comprising the electrodes and the paper matrix separator, modified with a highly concentrated dry potassium hydroxide salt, inside a flexible laminated plastic structure that provides sturdiness to the system making it safe and portable for the user. The battery turns on by applying 80 μl of water and as a result the system produces a maximum capacity of 0.5 mAh when 1.6 mA cm−2 are applied. The generated electrical power of two batteries in series is then used to power a LED during approximately one hour. Although there is room for improvement, these results allow envisaging the battery as a real commercial portable power source and allow planning potential uses of this energy to power microelectronics demanding low power consumption, such as sensors or wearable electronics.

As good alternatives for conventional rigid piezoelectric materials, piezoelectric nanocomposites combining piezoelectric materials and flexible polymer matrix demonstrate great potential for flexible nanogenerators. Rational design of the hybrid structure is important for performance optimization of piezoelectric nanocomposite. Here, we designed a hybrid piezoelectric paper through uniform assembly of vanadium doped ZnO (V-ZnO) mircoflowers in bacterial cellulose (BC) matrix by a in situ synthesis method. Different from pure ZnO where the c-axis of crystalline need to be oriented in order to get improved piezoelectric output, V-ZnO demonstrate ferroelectric property, which is prerequisite for poling with external high voltage in enhancing the output performance. The resultant hybrid paper demonstrated excellent flexibility and was used to fabricate flexible piezoelectric nanogenerators (PENGs). With excellent mechanical strength and durability, the V-ZnO/BC hybrid paper-based PENGs can work as self-powered motion sensors, which are capable of monitoring page-turning motions when integrated with pages of books. The V-ZnO/BC hybrid paper based PENGs are lightweight and inexpensive, which demonstrate promising applications for self-powered sensor networks and wearable electronics.

Graphene-based microsupercapacitors (mSCs) as important micro-power sources for miniaturized electronic devices have been a fascinating research topic. However, the large specific surface area of graphene is not fully exhibited due to the π-π stacking of graphene nanosheet in these graphene-based mSCs system fabricated by previously reported methods. Here, we propose a new method to fabricate the compact, flexible and all-solid-state graphene hydrogel-based mSC (GH-mSC) by combing paper chip with selective vacuum filtration, which allows the fabrication of mSCs with different sizes and shapes. The stack capacitance value of GH-mSC is 2.51 F cm−3 and the CV curve still keep quasi-rectangular even at a very high scan rate of 50000 mV s−1. The GH-mSC delivers acceptable energy densities of 0.223 mW h cm−3 and power densities of 0.024 W cm−3, which is better than electrolytic capacitor. Further, the GH-mSCs exhibit superior long-time cycling stability and good flexibility. More importantly, the mSC on paper chips allows easy scaling up of capacitance and output voltage by simply fabricating several mSCs on a plane or both sides of a paper and then connecting in parallel or series. These characteristics suggest that GH-mSCs are promising as power sources.

Paper-based SERS sensor has attracted considerable attention recently, resulting from the separation, aggregation and high sensitive detection of biomolecules. However, optical losses, caused by the holes or “vase”-like defects, affect the overall intensity of the electromagnetic (EM) coupling and then the Raman signal. Silver nanoflowers (AgNFs) connected with silver nanoparticles (AgNPs) arrays are proposed and firstly obtained onto such “vase” surface to enhance the EM coupling. AgNFs are easily self-assembled on the defects, and the closed packed AgNPs can be formed on the other area. Multiple cascaded amplification mechanisms (localized surface plasmon mode and optical standing waves or refraction) are used to promote the EM magnification. Such paper card is also exploited successfully as an integrated platform, allowing for ultra-sensitivity (1 × 10−19M) CV and (1 × 10−20M) R6G detection.

The strategies that require minimal resources, eco-friendly and readily available to a researcher are necessary for implementation of pervasive sensors. In this regard, a solvent-free frictional deposition of polymer is utilized to develop a chemiresistive ammonia gas sensor. The sensor was exposed to ammonia gas in the range of 200 ppb to 3.15 ppm concentration. The sensitivity of the sensor was found to be 20.5% ppm−1. The high sensitivity of ammonia sensor can be attributed to the rough surface of the film deposited on the paper. Being an eco-friendly and inexpensive approach, it can be used in the fabrication of maintenance-free disposable conducting polymer-gas sensors.

Flexible piezoelectric nanogenerators (PENGs) with high output performance are highly desirable for energy harvesting. Coupling triboelectric nanogenerators (TENGs) with the PENGs is a feasible method to enhance the output performance, while the complicated structure and the requirement of skillful operation limited the development of hybridized nanogenerators. In this work, flexible high-performance PENGs are developed using regenerated cellulose/BaTiO3 (C/BT) aerogel papers based polydimethylsiloxane (PDMS) nanocomposites. Benefiting from the high loading but uniform dispersion of tetragonal BT nanoparticles and the enhanced Young Modulus of the nanocomposites, the PENGs can exhibit a maximum voltage of 15.5 V and a maximum power of 11.8 μW under an external mechanical impact. By introducing a single electrode TENG, an innovative hybridized nanogenerator has been designed and prepared, which combine different mechanical energy harvesting techniques in a single device. Polarized along proper direction of the PENG, the positive coupling effect can efficiently increase the output voltage and power of the hybridized nanogenerator to 48 V and 85 μW, respectively. This research offers new insights into the design and preparation of high output hybridized nanogenerator with simple structure, high flexibility and easy operation.

L-tyrosine hydroxylase (TH) is a critical enzyme and involved in the conversion of L-tyrosine to L-3,4-dihydroxyphenylalanine (L-DOPA) in the human body. TH deficiency is a rare autosomal recessive disorder which results in cerebral catecholamine deficiency and causes symptoms of depression, movement disorders, and impaired development. L-DOPA is the common precursor of catecholamine neurotransmitters, therefore how to rapidly and precisely determine the ratio of L-DOPA to L-tyrosine in the bio-matrix is important to the clinical diagnosis of disorder. To response the demand, a low-cost, user-friendly, and on-site detection system is developed herein, which includes a wax-printing paper microfluidics as reaction platform, surface modification with sodium periodate for improving detection performance, an additive manufactured enclosed case for maintaining identical detection environment, and an IOS application (APP) to drive smartphone’s imaging to facilitate high-throughput quantification of multiple biomarkers simultaneously. Multiple experiments were conducted to understand the detection limit, detection range, shelf-life, and specificity of this quantification system even with a complex bio-matrix such as artificial urine or Fetal Bovine Sera (FBS). The experiment results showed that L-DOPA, L-tyrosine, and creatinine can be easily and rapidly quantified with high reliability and repeatability, demonstrating an efficient tool for routine checkup of patients with TH deficiency.

This study investigates heat integrated production of FT (Fischer-Tropsch) crude, where excess heat from the FT crude plant is delivered to a typical Scandinavian pulp and paper mill that produces fine paper. The sizes of FT crude plants are quantified, when the amount of excess heat from the FT plant exactly matches the heating demand otherwise satisfied by the bark boiler at the mill, considering a number of development pathways at the mill, including various degrees of steam savings and biorefinery options, such as lignin extraction. Performance of integrated production is compared with that of an FT stand-alone plant on the basis of wood fuel-to-FT crude efficiency, GHG (greenhouse gas) emissions balances and FT crude production cost. The results show that there exists a heat integration opportunity for an FT crude plant ranging from 0 up to 350 MW (LHV) of wood fuel depending on the development pathway for the mill. The results indicate higher overall efficiency and a generally lower production cost for the heat integrated, co-located production. Heat integrated production has a larger potential to contribute to GHG emission mitigation, assuming a future generation of grid electricity emitting equal to or less than an NGCC (natural gas combined cycle) power plant. © 2013 Elsevier Ltd. All rights reserved.

In this study, a pulp and paper mill (PPM) in the SEKA Papermaking Plant in Izmit, Turkey, is analysed through energy and exergy balances. The plant utilises recycled waste paper for papermaking. This type of raw material input makes the process highly sophisticated. The pulping uses strictly mechanical processes, such as digestion, separation by screening and hydrocyclone, and refining. The milling, as an integrated process, provides the final operations necessary to prepare the conditions required for the end-product by stock-preparation, wiring, rolling, and drying by dewatering, pressing, and evaporation. The possibility of making the entire process more thermodynamically efficient is discussed by calculating the energy and exergy losses for all the mechanical and physical sub-processes. The study shows that the energy efficiencies for each of the mechanical and physical steps in the PPM vary between 34% and 97.4%, whereas the exergy efficiencies vary between 30.2% and 94.2%. In conclusion, based on the results from the energy and exergy flow analyses, the exergy output can be improved through more efforts directed primarily to further measurements toward more efficient energy utilisation in the PPM.

Over the past few years, researchers have focused on stimulus-responsive soft materials and their applications in the design of soft actuators. The key factor of the soft actuators to achieve various applications is the programmable and controllable shape deformations. Here, a versatile and simple surface patterning method consisted of pencil drawing and pasting polymer films is proposed to design the soft actuators with programmable deformations. Due to the thermal expansion effect and the hygroexpansion effect, the graphite paper/polymer actuator performs a bending motion with a curvature of 1.4 cm−1 under light irradiation and 1.2 cm−1 under high humidity. Owing to the convenience of the patterning method, different patterns on both two surfaces of the paper substrate are designed without effort. Thus, through tuning the grayscale of the graphite on one surface of the paper, three types of T-shaped actuators can be obtained with different deformations under light irradiation. In addition, by pencil drawing or hydrophobically modifying specific patterns on the two surfaces of the paper, three types of strip-shaped actuators are also proposed to demonstrate that different 3D shape deformations can be obtained under different stimuli. Finally, a helix-shaped actuator inspired by the natural plant tendrils is fabricated by the thermal-induced shaping method. The helix-shaped actuator performs twisting/untwisting motion under different stimuli and can be used as a grasping robot. These results demonstrate the diversified programmability of the graphite paper/polymer actuator. Hence, the simple and versatile programming methods of soft actuators have great potential to be used in the field of biomimetic applications, intelligent robotics, and lab-on-paper devices.

It is generally accepted that the latest research findings are published as research papers in journals. Social network analysis (SNA) can offer a perspective from which to analyze technological developments. This work analyzes the development of lithium-ion batteries (LIBs) and electrolytes by SNA based on papers from 2011 to 2015. Three types of social networks, country-, institution-, and research paper-based networks were used. Country-based network analysis shows that major ten countries have a close relationship with respect to technology development. Institution-based network analysis revealed that 48 top institutions publish the most prolifically and that a “small-world” effect exists within the network, indicating excellent knowledge transfer among institutions through citations. Several institutions occupy the center position within the network and have a prominent influence in knowledge transfer as judged by centrality analysis. Research paper-based social networks, consisting of high-citation articles, are grouped into six technology clusters, which exhibit a broad range of knowledge transfer processes regardless of the battery and electrolyte types, indicating underlying closely interwoven relationships. The knowledge transfer path can describe the technology evolution in detail. An overview of technological development status can be thus obtained by this proposed three-level analysis method.

The optical model for reflectance lightness of stereo paper product surface is proposed, which could promote color reproduction study of paper model products and improving color reproduction quality. The reflectance lightness was measured using non-contact measurement method with spectroradiometer, CS2000A, that can measure stereo paper product surface lightness and tristimulus. Once inputting the paper product parameters of surface angle and tone, the model will predict the reflectance lightness for stereo paper product surface. After analyzing statistical information of light transmission, paper product surface reflectance lightness can be obtained. The results showed that prediction model is versatile and easy to use, besides the model quite approached to realistic paper product surface. The optical model simulation system could sufficiently accomplish reflectance lightness, which provides a novel way to predict and reproduce printing quality.