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The flexibility and insulating nature of polymeric dielectric materials are widely used in robotic and wearable electronic devices like electrical insulation, capacitive sensors, and electromechanical actuators. When combined with a phase transition-induced shape memory property, the resultant bistable electroactive polymer (BSEP) opens up new applications due to the rigid-to-rigid actuation of BSEP tremendously reducing the energy consumption for device operation while providing desirable strength for external loads. This dissertation focuses on investigating insulating, electroactive, and phase transition properties of BSEP, and adapting each aspect of the properties in the pursuit of innovative devices, such as rewritable photonic paper, smart windows with whole solar spectrum modulation, and wearable pressure sensors. An ink-free rewritable photonic paper has been invented through the interdisciplinary combination of photonic crystals, shape memory and electroactive properties of BSEP. The rewritable paper consists of a ferroferric oxide-carbon (Fe3O4@C) core–shell nanoparticle (NP)-based photonic crystal embedded in a BSEP. The nanocomposite can be repeatedly triggered to change into different shapes and colors due to the z-directional deformation that is induced by an electric field. The actuated shape and color can be maintained for a long term without energy input, and the stored images can then be rewritten over 500 times without noticeable degradation. Low energy consumption and simple erasing/rewriting are features that match the benefits of conventional paper as a zero-energy and long term data storage medium, but provide the additional advantage of rewritability. With pixelated electrode arrays, user-defined information can be actuated and erased at will which has been demonstrated through a seven-segment numerical display. A smart window with wide-band light modulation is designed solely based on the phase transition property of BSEP. One component of BSEP can be switched between semicrystalline and amorphous states through cooling below or heating above its melting temperature, leading to a reversible opaque-to-transparent transition. The opacity switching property of BSEP was further improved by mixing a more hydrophilic component to induce micro-scale phase separation, which is responsible for the whole solar spectrum light modulation due to Mie scattering. The resultant smart window achieves both high solar transmittance modulation of 70.2% and high luminous transmittance modulation of 80.4% which rivals the best reported smart windows and commercial privacy glasses with the highest privacy levels. This flexible smart window can also be mounted on curved surfaces for the need of windows with arbitrary shapes. This work is the first one to report an all-solid thermochromic smart window film without the inclusion of any metal/metal oxides or liquid crystals to enable a large light modulation over the whole solar spectrum.A flexible fiber-based pressure sensor is realized by applying a dielectric layer on the outside of a TEMPO-oxidized bacterial cellulose (TOBC)/silver nanowire (AgNW) conducting fiber. The pressure sensor can detect pressures up to 134 MPa with sensitivity of 101 � 10-4 kPa-1 due to its hierarchical structure and high conductivity. The porous structure of TOBC/AgNW helps increase the thickness deformation of the sensor with applied pressure, improving the sensing ability. Small pressures of human pulse and voice vibration can be detected with this sensitive pressure sensor. A machine learning classification model was implemented to recognize human’s speech where the prediction accuracy on a test dataset is > 90%. The ultrathin fibrous sensor (53 �m) is capable of high-resolution detection, and suitable as a comfortable and fashionable thread substitute for real wearable devices.The combined properties of BSEP with the proof-of-concept developments of rewritable paper, smart windows and wearable sensors demonstrate its potential for real-world applications. And an outlook for future research and suggested improvements for commercialization are discussed in the conclusion.

Bagasse sugarcane (BSC) has low fibre strength due to low cellulose content. Hence, by adding a strong secondary fibre that is high in cellulose such as pineapple leaf fibre (PALF), the fibre strength of the system can be improved. High portion of PALF decreased the composite paper performance because the high composition of PALF tends to produce flocs and agglomerates fibres. The arrangement of the fibres in composite paper should be improved so that this agglomerate’s effect could be overcome. A novel multilayer hybrid fibre composite was used. BSC/PALF with several hybrid ratios was studied in terms of the mechanical and moisture properties of the produced paper sheet and the results showed that multilayer hybrid composite paper produced higher in hybrid composite paper’s properties compared with random hybrid composite paper. The colour of multilayer hybrid fibre composite paper resembled the natural bright colour of BSC and the multilayer hybrid fibre composite paper also shown a slightly low weight loss percentage compared with the random hybrid fibre composite paper after 60 days of soil burial test. As a conclusion, multilayer hybrid fibre composite produced the stronger interfibre bonding and overcome the agglomerate’s effect between BSC/PALF compared with random hybrid fibre composite.

Selective detection and quantification of biomarkers related to human diseases are essential for preventive healthcare. Surface-enhanced Raman scattering (SERS) spectroscopy is a powerful analytical tool offering high sensitivity. However, the success of this promising analytical tool relies on the ability to effectively fabricate SERS substrate. Herein we have demonstrated a plasmonic paper-based flexible substrate (PPFS) for SERS sensing. In situ growth of silver nanostructures (AgNS) on the paper-based substrate was achieved by using a simple one-step silver mirror reaction (SMR). FESEM and TEM results depicts that the increasing silver ion content influences the morphology (growth of multifacets), as well as size of AgNS. Further, the PPFS substrate was tested with Rhodamine-6G (Rh-6G) dye and an attomole sensitivity with a LOD of 4.54 x 10-18 M was achieved. Further, two biomarkers, lactic acid (LA) and uric acid (UA) were detected on the PPFS substrate, with μM and pM sensitivity, having LOD values of 0.6 x 10-6 and 0.3 x 10-12 M respectively. Above detection levels for UA on PPFS is two orders better than reported values, whereas for LA it is comparable with reported substrates. Finally, UA, LA and their mixtures were tested on PPFS and results compared with commercial substrate. The performance of PPFS were found better in all cases, thus, multifaceted AgNS paper based PPFS offers the potential to be used as a biosensor for detection of various biomarkers from body fluids, responsible for the detection of the critical disease for preventive health care.

Statement of problem Quick response (QR) codes are a fast and efficient technology for linking and accessing identifying information, and their use has been proposed in forensics. The heat resistance and esthetics of denture marking methods (DMMs) have been recommended by the American Dental Association (ADA), but studies on these aspects of printed QR codes are lacking. Purpose The purpose of this study was to determine the optimal printed material with QR codes for implementation as a DMM adjusted to the recommendations of the ADA. Material and methods The behavior of 4 types of paper, bond paper, fiberglass filter paper, ultralong hydroxyapatite nanowire paper, and polyolefin and silica paper with printed QR codes was analyzed. They were exposed to temperatures between 100 °C and 1000 °C in a heat muffle for 1 hour. Each specimen was subjected to both a morphological and a thermogravimetric analysis (TGA) and scanned by using 3 different smartphones. Results The scans were positive for bond paper (33.3%), fiberglass fiber paper (50%), ultralong hydroxyapatite nanowire paper (100%), and polyolefin and silica paper (70.4%). The TGA revealed continuous decomposition curves (average 16.5 minutes at 624 °C). Conclusions Printed QR codes on ultralong hydroxyapatite nanowire paper appear to be suitable as information reservoirs, even surviving incineration, and may be implemented as a DMM conforming to the ADA recommendations.

Paper sheets represent one of the infection risk sources inside educational and administrative institutions under biological pandemics. So, the present study aimed to validate the efficiency of gamma radiation or dry heat techniques to sterilize contaminated paper sheets with different indicator pathogens while retaining their structure. The results showed that gamma radiation at 6, 12, or 24 kGy can successfully kill Gram-positive bacteria such as Bacillus cereus and Staphylococcus aureus, Gram-negative bacteria such as Escherichia coli and Salmonella typhi, and fungi such as Candida albicans. Moreover, dry heating at 100 °C for 60 min, 150 °C for 30 min, or 200 °C for 15 min can be successful in paper decontamination of all tested species. Surprisingly, scanning electron microscopy (SEM) micrographs proved that gamma radiation at 6 kGy, dry heat at 100 °C for 60 min or 150 °C for 30 min or 200 °C for 15 min, is suitable for paper sheet sterilization while maintaining their structure. Ultimately, dry heat is a simple, effective, fast, safe, and inexpensive technique for paper sterilization. It may be used as a precautionary step inside educational institutions, especially during written examination periods, to ensure a safe life for academic members during biological pandemics such as COVID-19.

Molybdenum sulfide (MoS2) with well-designed porous structure has the potential to be great electrode materials in sodium-ion batteries due to its high theoretical capacity and abundant resource, however, hindered by its intrinsic low conductivity and stability. Herein, MoS2 with 3D macroporous foam structure and high conductivity was obtained through SiO2 templates and integrated with carbon paper (3D F-MoS2/CP). It has showed superior specific capacity (225 mA h g−1, 0.4–3 V) and cycling stability (1000 cycles) at high rate (2000 mA g−1), with a low decay rate (0.033% per cycle) in sodium-ion batteries. The excellent electrochemical performance may originate from its unique integrated structure: 3D MoS2 macropores providing high surface area and abundant transfer channels while carbon paper enhancing the conductivity of MoS2 and avoiding unnecessary side reactions brought by binder addition.

The prevalence of diabetes has increased over the past years. Therefore, developing minimally invasive, user-friendly and cost-effective glucose biosensors is necessary especially in low-income and developing countries. Cellulose paper-based analytical devices have attracted the attention of many researchers due to affordability, not requiring trained personnel, and complex equipment. This paper describes a microfluidic paper-based analytical device for the detection of glucose in tear with the naked eye. The paper-based biosensor fabricated by laser CO2, and GOx/HRP enzymatic solution coupled with TMB was utilized as reagents. A sample volume of 10 µl was needed for the biosensor operation and the results were observable within 5 minutes. To evaluate the device performance, color intensity-based and distance-based results were analyzed by ImageJ and Tracker. Distance-based results showed a linear behavior in the range of 0.1–0.6 mM with an R2 = 0.967 and LOD of 0.2 mM. The results could be perceived by the naked eye without any need to further equipment or trained personnel in a relatively short time (3–5 minutes). Moreover, glucose concentration could be obtained non-invasively by tears collected by this µPAD.

Access to medical care is a significant challenge facing developing countries. The World Health Organization developed the ASSURED criteria, which specifies requirements for the ideal diagnostic. ASSURED stands for Affordable, Sensitive, Specific, Rapid/Robust, Equipment-free and Deliverable. Traditional microfluidic diagnostics (comprised of glass/PDMS) require expensive fabrication procedures and user-intervention to manipulate fluids on the device. For those reasons, paper shows great promise as a substrate for an ASSURED microfluidic diagnostic. It is affordable and does not require external pumping to move fluids. Initially, microfluidic paper-based analytical devices (μPADs) performed simple, colorimetric assays. However, the field has evolved rapidly. Modern μPADs have been developed for a plethora of applications such as nucleic acid amplification. Wider adaptation of μPADs relies on the incorporation of more complicated assays (i.e. involving multiple fluids), which would allow μPADs to replace more expensive benchtop equipment. This requires more robust fluid control. Typically, fluid control on μPADs has been achieved by slowing fluid down to create delays between different channels. However, adding delays increases overall assay time and creates other complications such as fluid loss due to evaporation. Instead, creating ‘delays’ by accelerating wicking (relative to native paper) is being investigated. Previous approaches include sandwiching the paper between polymer films or creating ‘macro capillaries’ within the paper for the liquid to flow through. Of particular interest is the etching of grooves onto paper channels using either a plotter or a CO2 laser. These grooves create hollow regions in the paper which lead to faster wicking speeds. This study aims to characterize the behavior of grooved channels in paper and assess their performance as ‘delay’ mechanisms for a multi-fluid paper-based sensor.Typically, μPAD designs evolve in a trial-and-error basis, where devices are fabricated, tested and updated. Having accurate models that characterize the imbibition process could streamline development by allowing direct translation of in-silico designs to fully-functioning paper-based tools. Current imbibition models do not adequately describe the complex transport phenomena occurring within the paper matrix. This study also aims to develop an in-silico simulation that can reliably predict imbibition in both native paper and grooved channels.

This manuscript aimed to enhance the mechanical, thermal, and ignition properties of bagasse paper when coated with different coatings synthesized from hydroxyethyl cellulose, 1,3-di-p-toluidine-2,2,2,4,4,4-hexachlorocyclodiphosph(V)azane, Talc powder, NaHCO3, cellulose nanocrystal. The effect of these coatings on the mechanical properties was studied by measuring elongation, tensile strength, and burst strength. The stages of degradation and ash residue of the measuring specimens were determined using thermal gravimetric analysis (TGA), behind that, the ignition properties as the flame chamber (UL/94), and limiting oxygen index (LOI) was measured according to standards. These tests proved that 1,3-di-p-toluidine-2,2,2,4,4,4-hexachlorocyclodiphosph(V)azane has a direct effect on improving the mechanical characteristics and enhancing the ignition properties of the coated specimens compared to uncoated. In this study the physical, mechanical, thermal, and ignition properties of the bagasse paper sheets were enhanced by easy and low-cost method via synthesis of new coatings based on commercially available chemicals in a reasonable cost.

Million tons of cellulosic paper have been used for insulating coils in oil-filled electrical power transformers, thereby assuring the electricity supply for our societies. The high working temperatures in transformers constantly degrade paper insulators throughout their service life of up to 40 years. We approached the structural changes in oil-immersed cellulosic paper samples upon thermal stress in a study that compared unbleached softwood Kraft paper used as insulator paper with pure cotton cellulose paper. The model experiments used a thermal treatment in transformer oil at 170 °C for up to 14 days. The samples were characterized by means of 13C CP/MAS NMR spectroscopy, mainly based on deconvolution of the C4 resonance. An automated, fast, and reproducible C4 resonance deconvolution employing the “Peak Analyzer” tool of OriginPro 2020 (OriginLab Corporation, USA) was developed and used to exploit 13C CP/MAS NMR spectroscopy for the characterization of thermally stressed paper samples. Our results show that thermally induced structural changes depend heavily on the composition of paper, that hornification and coalescence of fibrils take place, and that the allomorph composition of cellulose crystallites is altered under the given conditions. Graphical abstract