Self-assembly Of Cellulose Nanocrystals Research Articles

Synergistic color-changing and conductive photonic cellulose nanocrystal patches for sweat sensing with biodegradability and biocompatibility.

Given the ongoing requirements for versatility, sustainability, and biocompatibility in wearable applications, cellulose nanocrystal (CNC) photonic materials emerge as excellent candidates for multi-responsive wearable devices due to their tunable structural color, strong electron-donating capacity, and renewable nature. Nonetheless, most CNC-derived materials struggle to incorporate color-changing and electrical sensing into one system since the self-assembly of CNCs is incompatible with conventional conductive mediums. Here we report the design of a conductive photonic patch through constructing a CNC/polyvinyl alcohol hydrogel modulated by phytic acid (PA). The introduction of PA significantly enhances the hydrogen bonding interaction, resulting in the composite film with impressive flexibility (1.4 MJ m-3) and progressive color changes from blue, green, yellow, to ultimately red upon sweat wetting. Interestingly, this system simultaneously demonstrates selective and sensitive electrical sensing functions, as well as satisfactory biocompatibility, biodegradability, and breathability. Importantly, a proof-of-concept demonstration of a skin-adhesive patch is presented, where the optical and electrical dual-signal sweat sensing allows for intuitive visual and multimode electric localization of sweat accumulation during physical exercises. This innovative interactive strategy for monitoring human metabolites could offer a fresh perspective into the design of wearable health-sensing devices, while greatly expanding the applications of CNC-based photonic materials in medicine-related fields.

Multi-scale investigation of the effect of photocurable polyethylene glycol diacrylate (PEGDA) on the self-assembly of cellulose nanocrystals (CNCs)

Multi-scale investigation of the effect of photocurable polyethylene glycol diacrylate (PEGDA) on the self-assembly of cellulose nanocrystals (CNCs)

All-aqueous liquid crystal emulsions for 4D laser-printing of dual-stimuli response porous 3D printlets with on-demand remote control of drug release

The integration of responsive materials with 3D printing can lead to fabrication of functional smart 4D structures for use in health, biofabrication, and biosensing. Here, we utilized an all-aqueous two-phase system made from chitosan and carrageenan to create a bioactive all-water emulsion encapsulating curcumin to develop 4D printed 'prinlets' for possible drug delivery. Specifically, we described the production of an original all-aqueous cholesteric bicontinuous liquid crystal (LC) emulsion, which was accomplished by homogenizing or sonicating a rod-like cellulose nanocrystal (CNC) with two thermodynamically immiscible, phase-separating carrageenan and chitosan dispersions. Stable water-in-water emulsions were effectively prepared by mixing or sonicating the respective CNC/biopolymer dispersions, resulting in micrometric CNC/chitosan dispersed droplets (loaded with curcumin) in a CNC/carrageenan continuous phase. The LC-based emulsion showed a confined 3D percolating bicontinuous network with cholesteric self-assembly of CNCs within the carrageenan phase, while the nanoparticles in the chitosan phase remain isotropic. After laser 3D printing of the freeze-dried LC-based emulsion, 3D macroporous “printlets” encapsulated with curcumin were produced exhibiting a dual-stimuli-responsive to temperature and redox. The curcumin-loaded 3D 'printlets' exhibited superior thermosensitive properties and maintained a sustained drug release profile, exhibiting much greater on-demand release mode at human body temperature. Notably, the 3D porous “printlets” demonstrated a gated response to the aqueous environment, showcasing potential advancements in the realms of supramolecular sensors and drug delivery systems.

Rearrangement of cellulose molecular chains in situ for stabilizing two-dimensional nanochannels

Two-dimensional (2D) nanochannels originating from ordered stacking of nanosheets exhibit great potential in osmotic energy harvest, which provides a promising way to address the increasing energy crisis. Although polymer nanorods have unique advantages in constructing and adjusting 2D nanochannels, the stability of these nanochannels still faces great challenges. Herein, cellulose nanocrystal (CNC) nanorods are intercalated between graphene oxide (GO) nanosheets to construct 2D sub-nanochannels. Ordered sub-nanochannel structures are first formed through a vacuum assisted self-assembly of CNC and GO. A facile strategy involving the rearrangement of cellulose molecular chains in situ is subsequently employed to stabilize the dimensions and arrangement of the sub-nanochannels. After the rearrangement, the mechanical properties and water stability of the sample are greatly enhanced due to the increased dynamic hydrogen bond network, and tensile strength and strain at break are increased by 88.7% and 472.2%, respectively. Additionally, the prepared membrane exhibits a power density of 0.49 W m-2 under a 50-fold salinity gradient with a long-term stability and could be further improved to 0.75 W m-2 by reducing the ion transport distance. The photo-thermal conversion property of the membrane could also benefit the osmotic power generation. Our work opens new insights into stabilizing the dimensions and arrangement of 2D nanochannels constructed by nanorods and nanosheets for commercial osmotic power generation.

Modulation of Tannic Acid on the Cholesteric Structure of Cellulose Nanocrystals.

The chiral nematic phase structure, formed by the self-assembly of cellulose nanocrystals (CNCs) in an aqueous suspension and maintained in a solid film, shows great potential for optical applications. To achieve complex structures in optical devices, it is crucial to subject CNCs to specific shearing processes, such as spinning and printing. Understanding the structural and property changes of the CNC liquid crystal phase in these processes is of utmost importance. In this study, we investigated the effect of adding tannic acid (TA) on the rheological properties and cholesteric phase structures of CNCs/TA mixed suspensions. By calculating the surface site interaction points, we observed that TA can adsorb onto the surface of CNC rods in suspensions through hydrogen bonding. Through characterization techniques, such as polarized optical microscopy, rheology, and synchrotron SAXS, we examined the effects of TA addition on the microstructure and rheological properties of the CNC liquid crystal phase and clarified the change relating to the system composition. Under the same CNC concentration, the volume fraction of the anisotropic phase, the pitch, and the rod spacing of the cholesteric phase were not significantly affected by the addition of TA. However, the system viscosity was significantly reduced with the appropriate amount of TA (2 wt %), in a wide range of CNC concentrations (up to 15 wt % CNCs). The flow indexes (n) in Region I and Region III of steady-state shear curves of CNCs/TA systems (11-15 wt % CNCs) were compared. Moreover, we introduced the well-established theoretical models for liquid crystal polymers to tentatively interpret Region I of the CNCs/TA cholesteric phase and realized that increased numbers of smaller cholesteric-phase domains in the CNCs/TA system and interfacial modification by TA may contribute to the fluidity change. The feature of the domain texture of CNCs/TA systems is verified by polarized optical microscopy observations.

Birefringence Behaviors of Cellulose Nanocrystals under Varied Concentrations, Ultrasonication Treatments, and Different Solvents

Self-assembly of cellulose nanocrystal (NCC) in suspension has unique characteristics under polarize observation which is called as birefringence behaviors. However, the study about these phenomena is lacking especially when the NCC is prepared in dried powder form. Here, we reported the behaviors of commercial NCC obtained from CelluForce NCC, NCV100-NASD90 dispersed in different concentrations (0.1% to 8% weight/weight); ultrasonic times (0 to 45 minutes); solvents (Benzene, N,N-Dimethylacetamide (DMA), Ethanol, Dimethylformamide, Acetone, Acetic acid 1%, and Water) for their birefringence manners. In addition, nanocellulose obtained from TEMPO mediated oxidation and organic acid hydrolysis were also reported. Dried powder NCC showed shear thickening behavior at high concentration and well-dispersed at acetic acid and water solvent indicated the redispersable NCC. While, cellulose NCC, NCV100-NASD90 considerably low dispersion in non-polar solvents. Birefringence appears only when the suspension was in anisotropic state due to stirring. As sonication times increased, the birefringence clearly visible which suggested the defibrillation of aggregated cellulose crystal. The results of this study authenticated that redispersable NCC could be obtained from dried powder cellulose and provided birefringence behavior by managing concentration levels, sonication times and perfect solvents to dilute.

Robust Cellulose Nanocrystal-Based Self-Assembled Composite Membranes Doped with Polyvinyl Alcohol and Graphene Oxide for Osmotic Energy Harvesting.

Osmotic energy from the salinity gradients represents a promising energy resource with stable and sustainable characteristics. Nanofluidic membranes can be considered as powerful alternatives to the traditional low-performance ion exchange membrane to achieve high-efficiency osmotic energy harvesting. However, the development of a highly efficient and easily scalable core membrane component from low-cost raw materials remains challenging. Here, a composite membrane based on the self-assembly of cellulose nanocrystals (CNCs) with polyvinyl alcohol (PVA) and graphene oxide (GO) nanoflakes as additives is developed to provide a solution. The introduction of soft PVA polymer significantly improves the mechanical strength and water stability of the composite membrane by forming a nacre-like structure. Benefiting from the abundant negative charges of CNC nanorods and GO nanoflakes and the generated network nanochannels, the composite membrane demonstrates a good cation-selective transport capacity, thus contributing to an optimal osmotic energy conversion of 6.5W m-2 under a 100-fold salinity gradient and an exemplary stability throughout 25 consecutive days of operation. This work provides an option for the development of nanofluidic membranes that can be easily produced on a large scale from well-resourced and sustainable biomass materials for high-efficiency osmotic energy conversion.

Bouligand nanocomposites: Self-assembly of cellulose nanocrystals with a thermo-responsive polymer

Cellulose nanocrystals (CNCs) naturally self-assemble into helical structures that effectively deflect crack propagation and exhibit structural coloration based on the pitch. To further tune the structural coloration via environmental conditions, a thermoresponsive polymer poly(diethylene glycol methyl methacrylate) (PMEO2MA) was incorporated into CNC composites. Nanocomposite films of PMEO2MA-CNC with 0–30 mass % PMEO2MA loadings were prepared via controlled evaporation-induced self-assembly. As the polymer infiltrates CNCs' helical structure, the resulting films’ reflectance wavelength transitions from blue to red. PMEO2MA-CNC nanocomposites exhibited reversible temperature responses in the solid-state between 26 °C and 29 °C under variable humidity conditions, demonstrating the tunability of the self-assembled films. Fluorescence lifetime imaging microscopy (FLIM) provided insights to polymer dynamics in response to temperature.

Self-assembly of cellulose nanocrystals on flexible fabric via a metal coordination strategy for versatile applications

Cotton fabric is widely found in nature, and its outstanding breathability, flexibility, and rich surface groups have encouraged material scientists to investigate it. Self-assembly on the surface of cotton fabrics is an ingenious strategy for developing value-added textiles with special functionalities. This study reports a facile, low-cost technique for directing modified cellulose nanocrystal (CNC) self-assembly by copper ions on the surface of cotton fabrics. Uniform dense sea urchin-like modified CNC agglomerates were formed on the fibres surface, which greatly increased itsspecific surface area. Due to the involvement of Cu2+ in the chelation process and the high specific surface area of the micro-nano structure, the antibacterial effect of this coated fabric was up to 99.9 %. Meanwhile, its water stability was greatly improved by secondary treatment with perfluorooctylethyltrimethoxysilane, extending the potential applications of the self-assembled coating. The results showed that the water contact angle of the coated fabric reached 160° ± 0.5°, and the construction of the micro-nano surface structure enabled it to absorb 3 and 5 times of its own weight of n-heptane and carbon tetrachloride. In addition, the coated fabric also has excellent mechanical stability and chemical durability, shows self-cleaning, oil-water separation and many other properties. At the same time, the breaking strength and wearability of the fabric have been improved after the nano-organic coating finishing. Combining the advantages of flexible fabrics and organic nanofillers, coated fabric is expected to bring traditional textiles to the fore in areas such as stain protection, safety, and health care.

Sustainable, Insoluble, and Photonic Cellulose Nanocrystal Patches for Calcium Ion Sensing in Sweat.

Self-assembly of cellulose nanocrystals (CNCs) is invaluable for the development of sustainable optics and photonics. However, the functional failure of CNC-derived materials in humid or liquid environments inevitably impairs their development in biomedicine, membrane separation, environmental monitoring, and wearable devices. Here, a facile and robust method to fabricate insoluble hydrogels in a self-assembled CNC-polyvinyl alcohol (PVA) system is reported. Due to the reconstruction of inter- or intra-molecular hydrogen bond interactions, thermal dehydration makes an optimized CNC/PVA photonic film form a stable hydrogel network in an aqueous solution rather than dissolve. Notably, the resulting hydrogel exhibits superb mechanical performance (stress up to 3.3 Mpa and tough up to 0.73MJm-3 ) and reversible conversion between dry and wet states, enabling it convenient for specific functionalization. Sodium alginate (SA) can be adsorbed into the CNC photonic structure by swelling dry CNC/PVA film in a SA solution. The prepared hydrogel showcases the comprehensive properties of freezing resistance (-20°C), strong adhesion, satisfactory biocompatibility, and highly sensitive and selective Ca2+ sensing. The material could act as a portable wearable patch on the skin for the continuous analysis of calcium trends during different physical exercises, facilitating their development in precision nutrition and health monitoring.

All-Aqueous Bicontinuous Structured Liquid Crystal Emulsion through Intraphase Trapping of Cellulose Nanoparticles.

Here, we describe the all-aqueous bicontinuous emulsions with cholesteric liquid crystal domains through hierarchical colloidal self-assembly of nanoparticles. This is achieved by homogenization of a rod-like cellulose nanocrystal (CNC) with two immiscible, phase separating polyethylene glycol (PEG) and dextran polymer solutions. The dispersed CNCs exhibit unequal affinity for the binary polymer mixtures that depends on the balance of osmotic and chemical potential between the two phases. Once at the critical concentration, CNC particles are constrained within one component of the polymer phases and self-assemble into a cholesteric organization. The obtained liquid crystal emulsion demonstrates a confined three-dimensional percolating bicontinuous network with cholesteric self-assembly of CNC within the PEG phase; meanwhile, the nanoparticles in the dextran phase remain isotropic instead. Our results provide an alternative way to arrest bicontinuous structures through intraphase trapping and assembling of nanoparticles, which is a viable and flexible route to extend for a wide range of colloidal systems.

Controlling superstructure formation and macro-scale adhesion via confined evaporation of cellulose nanocrystals

The self-assembly of cellulose nanocrystals can tether their interfacial interactions and the associated properties of their constructs. For instance, assemblies of highly aligned cellulose nanocrystals (CNCs) bear improved mechanical strength, barrier properties, and piezoelectric response. In this study, the self-assembly of CNC superstructure was assessed under various confinement geometries, enabling optimization of the long-range order within the microstructures formed. The confinement involved the planar capillary (with a rectangular cross-section)formed between two glass substrates with silicone boundaries. The impact of temperature, width and thickness of the capillary plane on self-assembly of the micro-scaled lamellar structures was evaluated. Thinner capillaries and lower temperatures were found to considerably improve long-range order and increase the frequency of the periodic microstructures formed. The drying process was monitored by rheological analysis, which showed an initial fast drying followed by slow drying due to the hindered diffusion through lamellae. The adhesive properties of the formed superstructures were evaluated. The shear strength was shown to depend on the orientation of the superstructures and therefore of the CNCs. About 4 MPa adhesion strength was obtained when the lamellar superstructures were perpendicularly aligned with respect to the in-plane force applied, while ca. 3 MPa adhesion was obtained for parallel alignment. The experimental framework described herein enabled the evaluation of the impact of the dimensions of a drying meniscus on self-assembly of anisometric colloids while also linking cellulosic assemblies with their interfacial supramolecular interactions. This simple framework brings forward the possibility to correlate the behavior of nanometric objects with micro- and macro-scaled observations, e.g., macro-scaled mechanics of adhesion.

Bioinspired Chiral Template Guided Mineralization for Biophotonic Structural Materials.

Nature provides numerous biomineral design inspirations for constructing structural materials with desired functionalities. However, large-scale production of damage-tolerant Bouligand structural materials with biologically comparable photonics remains a longstanding challenge. Here, an efficient and scalable artificial molting strategy, based on self-assembly of cellulose nanocrystals and subsequent mineralization of amorphous calcium carbonate, is developed to produce biomimetic materials with an exceptional combination of mechanical and photonic properties that are usually mutually exclusive in synthetic materials. These biomimetic composites exhibit tunable mechanics from "strong and flexible", whichexceeds the benchmark of natural chiral materials, to "stiff and hard", which is comparable to natural and synthetic counterparts. Especially, the biomimetic composites possess ultrahigh stiffness of 2GPa in their fully water-swollen state-a value well beyond hydrated crab exoskeleton, cartilage, tendon, and stiffest synthetic hydrogels, combined with exceptional strength and resilience. Additionally, these composites are distinguished by the tunable chiral structural color and water-triggered switchable photonics that are absent in most artificial mineralized materials, as well as unique hydroplastic properties. This study opens the door for a scalable synthesis of resilient biophotonic structural materials in practical bulk form.

Non-iridescent and Wide-Color-Range Structural Coloration Enabled by Cellulose Nanocrystals with a Controlled Long-Range Photonic Structure and Helical Pitch

Bioinspired coloration of cellulose nanocrystals (CNCs) has advanced a new era of wide applications for decoration, sensing, and anti-counterfeiting. However, the solid structural color films suffer from strong angle-dependent iridescence and a limited color range due to the spatial arrangement caused by kinetic arrest during evaporation-induced self-assembly of CNCs. Here, a ternary co-assembly approach is demonstrated to prepare CNC films with weak/non-angular optical response and wide-range colors. Structural coloration is enabled by the long-range and short-range ordered photonic structure of CNCs. A cationic polymer, poly(dimethyl diallyl ammonium chloride), is introduced to influence the CNC self-assembly through electrostatic attraction, inducing the structural transition to the long-range disordered/short-range ordered structure as well as presenting the gradual change from iridescent structural colors to non-iridescent colors. Additionally, a hydrophilic small compound, glycerol, is used to adjust the helical pitch of nanostructured CNC arrays, offering the broad-range coloration. The CNC-based composite material is further used as an optical coating for anti-counterfeiting and realizing color patterning and angle-dependent selective color changes.

A cellulose nanocrystal templating approach to synthesize size-controlled gold nanoparticles with high catalytic activity

Advanced templating methods have shown precise regulation of the micro/nanostructures of inorganic catalysts. Here, on the basis of controlled self-assembly and micro-structures of cellulose nanocrystals (CNCs), a new bio-mass-mediated templating approach is proposed to control the growth of gold nanoparticles (Au NPs). The catalytic performance of the as-prepared Au NPs was evaluated using p-nitrophenol as a model pollutant. TEM, POM, zeta-potential, and rheological measurements were conducted to investigate the structure and catalytic activity of the nano-materials. By regulating the chiral nematic liquid crystal texture formed by the self-assembly of CNCs, the size of Au NPs could be adjusted at the nanoscale dimension, from 1.38 ± 0.38 nm to 4.25 ± 1.24 nm. Depending on the Au size, a high catalytic effect, namely, 98.0% conversion rate, was obtained within 30 min. The conversion rate was maintained at 97.0% even after 3-run cyclic application. Such findings demonstrate the potential of using CNCs as a bio-template to control the growth of nanomaterials.

Fast Self‐Assembly of Scalable Photonic Cellulose Nanocrystals and Hybrid Films via Electrophoresis

Nano-enabled, bio-based, functional materials are key for the transition to a sustainable society as they can be used, owing to both their performance and nontoxicity, to gradually replace existing nonrenewable engineering materials. Cellulose nanocrystals (CNCs), produced by acid hydrolysis of cellulosic biomass, have been shown to possess distinct self-assembly, optical, and electromechanical properties, and are anticipated to play an important role in the fabrication of photonic, optoelectronic, and functional hybrid materials. To facilitate CNCs' technological viability, a method suitable for industrial exploitation is developed to produce photonic films possessing long-range chirality on conductive, rigid, or flexible, substrates within a few minutes. The approach is based on electrophoretic deposition (EPD)-induced self-assembly of CNCs, where photonic films of any size can be produced by controlling CNC surface properties and EPD parameters. CNC film coloration can be determined by the CNC aqueous suspension characteristics, while their reflected intensity can be tuned by changing the duration and number of electrodeposition cycles. EPD-induced self-assembly of CNCs is compatible with in situ reduction of gold precursors without the need to use additional reducing agents (some of which are considered toxic), thereby allowing the preparation of hybrid photonic films with tunable plasmonic response in a one-pot process.

Self-Assembly of Cellulose Nanocrystals and Organic Colored Pigments as Reinforcement Matrix of Lipstick for Enhancing SPF.

The vermilion of the human lip, covered by a skinny epithelium with little melanin, is quite susceptible to damage from ultraviolet (UV) radiation exposure. However, commercial sunscreen filters and indelible dyes used in lipsticks can cause health hazards after percutaneous absorption or accidentally oral administration. Inspired by plant pigmentation as natural filters to protect themselves against overexposure to UV, safer bio-based sunscreens of cellulose enveloped with anthocyanin (AN) were developed using bionic design. Cellulose nanocrystals (CNC), derived from acid hydrolysis of cellulose, reinforced enhancement of UV absorption and shielding properties of AN. This innovation addresses the issue that naturally sourced UV filter application to sunscreen does not achieve a desired sun protection factor (SPF) value because of the low specific extinction value (E1,1). We also stated that the diverse formula of anthocyanin sunscreen lipsticks with CNC exhibited 10 times more SPF value than AN alone. Furthermore, they possess competitive benefits such as pleasing texture, superior adhesion, impermeable, nonphototoxicity, ease of application, and removal. This work provides a promising proof-of-concept for studying the features of natural sunscreens in the design of simple, safe, efficient, and green sunscreens.

Distinct liquid crystal self-assembly behavior of cellulose nanocrystals functionalized with ionic liquids

Rod-like cellulose nanocrystals (CNCs) show the intriguing liquid crystal self-assembly ability. The understanding of the self-assembly behavior of CNCs is of fundamental importance for constructing cellulose-based functional materials. The presented work explores how the liquid crystal self-assembly behavior of CNCs is affected by the grafted ionic liquids (IL) [VBIm][BF4]. The results demonstrate that the IL modified CNC (CNC-IL) with positive charged form chiral nematic structure in suspensions, which was normally observed in negative charged ones. Significantly, such liquid-crystalline organization can be obtained under much lower concentration (as low as 1.0 wt%) than that of the non-functionalized CNCs prepared from paper pulp (~ 3.0 wt%). Moreover, for CNC-IL concentrations varying from 1.0 to 4.0 wt%, the tactoids (showing obvious fingerprint texture) coexist with the disordered CNC phase, rather than separating into two phases. Unlike original CNCs, the pitch of chiral nematic tactoids increases with increasing concentration of CNC-IL. Our study suggests that the distinct liquid crystal self-assembly behavior of CNC-IL is related to the restricted mobility of CNCs rods due to the increase in CNCs particle size and the high viscosity of CNC-IL suspension as the result of IL surface modification. The study of the liquid crystal assembly behavior of IL modified CNCs provides some new insight to understand the intriguing chiral nematic self-assembly of CNCs and for construction of CNC-IL reinforced nanocomposites.

Efficient transition metal dichalcogenides exfoliation by cellulose nanocrystals for ultrabroad-pH/temp stable aqueous dispersions and multi-responsive photonic films

A major challenge in developing 2D transition-metal dichalcogenides nanosheets (TMD ns) as nanofillers, catalysts and photothermal reagents lies in its colloidal stability and scalable production. Herein, a biomimetic hybrid strategy to efficiently exfoliate and stably disperse TMD ns in a low-cost, environment-friendly manner is demonstrated. Cellulose nanocrystal (CNC) with controllable morphology and surface chemistry is acted as ideal assisted exfoliation reagent and stabilizer for highly concentrated and thin-layer TMD ns aqueous dispersions. Ultrabroad-pH/temperature (pH = 1–13, temperature = 1–95 °C) stable aqueous dispersions of TMD ns/CNC hybrids and the self-assembly of CNC allow the successful construction of flexible, rapid, and multi-stimuli responsive photonic films, e.g., mechanical strain, humidity and photothermal, providing an avenue for artificial skin, flexible sensor, and smart screen & window applications.

Lateral Gradient Ambidextrous Optical Reflection in Self-Organized Left-Handed Chiral Nematic Cellulose Nanocrystals Films.

Artificial photonic materials displaying ordered reflected color patterns are desirable in the field of photonic technologies, however, it is challenging to realize. Here we present that self-assembly of cellulose nanocrystals (CNC) in a tilted cuvette leads to the formation of rainbow color CNC films. We show that the self-organized CNC films enable simultaneous reflection of left-handed circularly polarized (LCP) and right-handed circularly polarized (RCP) light with lateral gradient transmittance ratio (LCP/RCP: 8.7–0.9) and the maximum reflectance value up to ca. 72%. This unique ambidextrous optical reflection arises from left-handed chiral photonic architectures with lateral gradient photonic bandgaps and nematic-like defects at the film-substrate interface and between left-handed photonic bandgap layers acting as a half-wavelength retarder. We demonstrate that the tilted angle self-assembly method provides a feasible step toward color patterning of CNC-based photonic films capable of ambidextrous optical reflection.