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Engendering stimuli-responsive and green shapable materials is a critical aspect of intelligent, responsive packaging technologies. Thermochromism, i.e., the optical response of materials to thermal stimuli, merges the visual appearance of the packaging with the temperature of the surroundings and cargo. Herein, sustainable, functional two-dimensional (2D) and three-dimensional (3D) hybrids of natural nanoribbons, i.e., cellulose nanofibrils (CNFs) and ionic liquids (ILs), were introduced as highly porous hydrothermochromic nanofoams, spheres, and flexible films. Hygroscopic ILs of nickel (II) or chromium (III) salts and imidazolium derivatives (1-ethyl-3-methylimidazolium chloride) were incorporated into the nanofibrils network, driving reversible color-switching via moisture adsorption controlled by temperature (hydrothermochromism, HTC). Multicolored HTC hybrids with a vast and adjustable color range from pale green to blue and from green to red with a color transition at 20 °C–80 °C were obtained by tailoring the composition (nickel and chromium chloride chemistry) and shape of the CNF–IL samples. These humidity- and temperature-responsive hybrids derived from biobased nanomaterials can pave the way toward future green smart packaging, which meets the requirements of sustainable development. The hybrids also provide advanced performance by monitoring and responding to the conditions of items and the surroundings.

Owing to the intrinsic hydrophilicity of nanocellulose, films and nanopapers prepared from cellulosic nanomaterials exhibit weak mechanical strength when exposed to high-moisture conditions. In this study, an approach for designing a water resistant, assembled nanopaper through controlled and irreversible aqueous complexation of oppositely charged cellulose nanoconstituents, i.e., cationic cellulose nanocrystals (AH-CNC) and anionic cellulose nanofibers (TO-CNF), is proposed. The fabrication process and features of the nanopaper can be adjusted by altering of the AH-CNC/TO-CNF ratio. For example, the draining time during the filtration of a nanopaper decreased dramatically (480–10 min) when the dosage of nanocelluloses resulted in charge compensation. This dosage also reduced the swelling of the nanopaper. After all charged groups were neutralized, a nanopaper with a wet strength of 11 ± 3 MPa was obtained when immersed in water for 24 h. Furthermore, the electrostatic interaction between the charged nano-entities enhanced the mechanical properties of the nanopaper in dry state (the maximum of tensile strength was 174 ± 3 MPa) and resulted in improved water barrier properties (water vapor transmission rate of 1683 g μm m⁻² d⁻¹). This straightforward method based on simply aqueous mixing of two oppositely charged nanomaterials may provide a new pathway for the fabrication of various functionalized films and sheets with advanced characteristics from different type of charged nanoparticles and colloids.

In this work, deep eutectic solvent (DES) based on imidazole and triethylmethylammonium chloride was used as a reaction medium for the esterification of cellulose nanofiber (CNF) and all-cellulose composite (ACC) films with n-octylsuccinic anhydride (OSA) to obtain high strength and sustainable films with increased hydrophobicity. Diffuse reflectance infrared Fourier transform spectroscopy and X-ray photoelectron spectroscopy were used to prove the success of the modification. The mechanical strength of the modified films was analyzed in dry, humid, and wet conditions, and the hydrophobicity of the films was indicated in terms of contact angle measurements. In addition, water absorption and transparency of the films were characterized. The modification was proven to be simple and fast, and mild conditions of 80 °C reaction temperature and 1 h reaction time were used. DES/OSA- modified CNF film exhibited better mechanical properties in dry, humid, and wet conditions compared to reference CNF film, and DES/OSA-modified ACC film displayed notable higher mechanical properties in wet state compared to that of reference CNF film (31 MPa tensile strength and 6.1% strain at break vs. 18 MPa and 2.2%, respectively). These improvements were partly attributed to higher contact angles of modified films (ACC-DES/OSA 60° and CNF-DES/OSA 51°) compared to CNF film (37°).

Lignocellulose is a potential raw material for film and membrane applications, such as packaging for every day consumables or a supporting barrier layer for flexible electronics. Here, lignin-containing cationic wood nanofiber (CWNF) films were produced using sawdust as the starting material. Sawdust was directly cationized using four different aqueous solvents containing tetraethylammonium hydroxide with different carbamides (urea, methylurea, ethylurea, or dimethylurea) and glycidyltrimethylammonium chloride as the cationization agent. Cationic wood was obtained with a high cationic group content (around 1.5 mmol g−1) and yield (89–100%), and CWNFs were easily obtained by mechanical disintegration as a water suspension. The films produced using solvent-casting exhibited excellent visible-light transparence (around 80% at 600 nm), and the presence of lignin allowed high UV-adsorption (below 380 nm, transmittance was under 1%). The films showed high oxygen barrier properties (below 400 and 4000 m3 μm/m2 day atm at a relative humidity of 50 and 92%, respectively) and good mechanical strength. An antimicrobial test conducted using the disk method showed that the CWNF films exhibited bacterial anti-adhesive properties with a small inhibition zone. CWNFs are therefore potential environmentally friendly packaging materials to prevent food spoilage, or useful as a UV-absorption layer for electronic devices such as solar cells.

Tissue paper softness relies on two major factors, the bulk softness, which can be indicated by the elasticity of the sheet, and surface softness. Measurement of surface softness is complicated and often requires a multi-step process. A key parameter defining surface softness is the topography of the surface, particularly the crepe structure and its periodicity. Herein, we present a novel approach to measure and quantify the tissue paper surface crepe structure and periodicity based on the detection of waviness along the sample using laser scanning confocal microscopy (LSM) and X-ray tomography (XRT). In addition, field emission scanning electron microscope (FESEM) was used to characterize the tissue paper surface. We demonstrate that surface topography is directly correlated to the erosion of the doctor blade, which is used to remove the dry tissue paper from the Yankee cylinder. Because of its accuracy and simplicity, the laser confocal microscopy method has the potential to be used directly on the production line to monitor the production process of the tissue paper. XRT revealed more structural details of the tissue paper structure in 3D, and it allowed for the reconstruction of the surface and the internal structure of the tissue paper.

Organic-inorganic hybrid films were fabricated from cellulose nanofibrils (CNF) and nanosilica (5–30% wt) embedded in a chitosan (Chi) biopolymer matrix using a slow evaporation method. The self-standing films exhibited high strength and modulus up to 120 ± 5 MPa and 7.5 ± 0.4 GPa, respectively, which are remarkably high values for biopolymer/chitosan hybrids. Scanning electron microscopy showed that the nanosilica is formed of larger aggregates within the lamellar CNF network structure. This observation was further confirmed using synchrotron-based scanning transmission x-ray microscopy (STXM) with the capability to determine the spatial and chemical distribution analysis of the constituents of films. It is interesting that the thermal stability of the hybrid films improved as the nanosilica content increased. Furthermore, the nanosilica effectively filled the pores in the CNF network, thus decreasing the UV transmission and the visible light transmittance of the films.

This paper presents novel loss quantization of reflectarray elements based on organic substrate materials. Three differently composed substrate materials derived from recycled materials have been characterized for their dielectric properties using a broadband analysis technique. The materials show low dielectric permittivity values of 1.81, 1.62 and 1.84 for X-band frequency range. In order to estimate the reflection loss of for the three substrates a mathematical relation has been established using empirical data generated by computer simulated models. The reliability of the proposed model has been established by simulation and fabrication of unit reflectarray rectangular patch elements on three proposed substrate substrates. A broadband frequency response has been depicted by scattering parameter analysis of unit elements with 10% fractional bandwidth of 312, 340 and 207 MHz for RCP50, RCR75 and RNP50 substrate respectively

A novel design of a dual frequency single layer reflectarray antenna is presented for X-band frequency applications. Dual U slots embedded on conventional rectangular microstrip reflectarray have been designed to attain a dual frequency operation. A detailed analysis of the effect on surface current distributions with the introduction of dual U slots is presented. Moreover a parametric study on the variation of significant dimensions of the design have been carried out and analysed thoroughly using a commercially available CST computer model. Proposed design configurations were fabricated above a 0.508 mm thick substrate of Rogers Duroid 5880. The dual U slot configuration offers a significant dual frequency behavior at 8.54 and 11.56 GHz with 10% bandwidth improvement of 47 and 56 MHz with a reflection loss of -4.54 and 4.11 dB respectively.

Focus improvement activity was employed to improve front-end assembly yield in integrated circuit packaging. The top three yield losses in parts per million (ppm) in front-end assembly were contributed by the following defects: non-stick on pad (NSOP) (2715 ppm), chip and crack (782 ppm) and missing wire (687 ppm). NSOP was due to floating die, bonded ball small in size, foreign matter on pad and glassifications. Floating die contributed 48% of the NSOP defect. Detailed explanation on how focus improvement activity used to reduce NSOP due to floating die is demonstrated. Upon identifying the root cause of die floating, which was due to no support and weakness in the vacuum system, actions were taken to eliminate and to control the identified causes. As a result NSOP due to floating die was reduced from 1300 ppm to 650 ppm, a reduction of 50% within one year.

This paper presents the design of a low RCS reflectarray at 8.52 GHz by replacing the solid metal sheet behind the antenna with a band stop frequency selective surface. A 50 element linear array of omni-directional elements was used to simulate the far field pattern of a reflectarray with f/D=0.325 in the plane of the elements to assess the effect of an imperfect aperture distribution on the gain and sidelobe levels. It is found that the reflection loss variation across the aperture does not have a significant effect on the radiation pattern of the antenna, because for the layout that was studied, only a few of resonant loops were predicted to give a significantly different loss than the others in the array. Simulated and measured results show that the ‘in-band’ reflection phase response of the structure with metal ground plane and with a periodic FSS ground plane is very similar, however the periodic ground plane reduces the ‘out of band’ reflectivity by more than 4 dB, thereby decreasing its RCS profile to these signals.

An investigation of phase variation and phase range of concentric split ring square element for broadband reflectarray antenna is presented in this paper. This is realized by exploiting the physical geometry of three element shapes namely square element, concentric ring square element and concentric split ring square element. Modifying the current distribution of basic concentric ring square element, leads to a less steep phase variation and also the bandwidth performance. An analysis of frequency response is described and analysed. The physical interpretation of the elements is also discussed. The proposed antenna element effectively covers two frequency operations (13.44 GHz and 18.36 GHz) in Ku-band range. Bandwidth broadening is achieved by introducing the ring square combination of element and the practical phase range is achieved through the use of RF 35 (thickness = 1.524 mm) as the substrate. The new concept of split initiates to a wider bandwidth (up to 67.6 %) for the antenna and can applied to any two frequency operations of Ku-band applications.