Flat Surface Research Articles

Tuning surface morphology of AuNPs film via thiourea as a stable SERS platform for methylene blue

Gold nanoparticles (AuNPs) have been extensively utilized in various fields such as sensors, life sciences, and catalysis. In this study, AuNPs were synthesized using a reduction method and subsequently treated with thiourea in an ethanol-water environment to prepare AuNPs film using a centrifugal deposition method for first time, resulting in the aggregation of the initial small-sized AuNPs into larger microsphere-like structures. The addition of thiourea facilitated the interconnection between AuNPs, ultimately leading to the formation of large stable gold microspheres. The sheet resistance of the AuNP films transitioned from being non-conductive to exhibiting a sheet resistance of 42.6 Ω/sq following thiourea treatment. The transformation from a flat surface to tightly connected particles resembling microspheres was observed from SEM images. The thiourea treatment not only altered the morphological characteristic of the AuNPs films but also significantly increased the number of scattering sites on their surface, leading to a substantial enhancement in the Raman scattering effect for methylene blue. This structural configuration also improved the electronic conduction and stability of the treated AuNPs films. Consequently, these findings suggest that AuNPs have promising application prospects in surface-enhanced Raman scatting (SERS), as well as in flexible electronics, catalysis, adsorption, and energy fields.

Magnetic Torque-Driven All-Terrain Microrobots.

All-terrain microrobots possess significant potential in modern medical applications due to their superior maneuverability in complex terrains and confined spaces. However, conventional microrobots often struggle with adaptability and operational difficulties in variable environments. This study introduces a magnetic torque-driven all-terrain multiped microrobot (MTMR) to address these challenges. By coupling the structure's multiple symmetries with different uniform magnetic fields, such as rotating and oscillating fields, the MTMR demonstrates various locomotion modes, including rolling, tumbling, walking, jumping, and their combinations. Experimental results indicate that the robot can navigate diverse terrains, including flat surfaces, steep slopes (up to 75°), and gaps over twice its body height. Additionally, the MTMR performs well in confined spaces, capable of passing through slits (0.1 body length) and low tunnels (0.25 body length). The robot shows potential for clinical applications like minimally invasive hemostasis in internal bleeding and thrombus removal from blood vessels through accurate cargo manipulation capability. Moreover, the MTMR can carry temperature sensors to monitor environmental temperature changes in real time while simultaneously manipulating objects, displaying its potential for in-situ sensing and parallel task implementation. This all-terrain microrobot technology demonstrates notable adaptability and versatility, providing a solid foundation for practical applications in interventional medicine.

Polyvinyl alcohol-chitosan based oleanolic acid nanofibers against bacterial infection: In vitro studies and in vivo evaluation by optical and laser Doppler imaging modalities

The present work focuses on the fabrication of polyvinyl alcohol-chitosan-loaded oleanolic acid-nanofibers (PVA-CS-OLA-NFs) for bacterial infection. The prepared PVA-CS-OLA-NFs were characterized for contact angle, SEM, AFM, XRD, FTIR, and TGA. The solid-state characterization and in vitro performance evaluation of nanofibers reveal consistent interconnection and diameters ranging from 102 ± 9.5 to 386 ± 11.6 nm. The nanofibers have a flat surface topography and exhibit efficient drug entrapment. Moreover, the in vitro release profile of PVA-CS-OLA-NFs was found to be 51.82 ± 1.49 % at 24 h. Furthermore, the hemocompatibility study showed that the developed PVA-CS-OLA-NFs are non-hemolytic to human blood. The PVA-CS-OLA-NFs demonstrate remarkable antibacterial capabilities, as evidenced by their MBC and MIC values, which range from 128 and 32 μg/mL, against the strains of S. aureus. The in-vivo fluorescence optical imaging showed the sustained PVA-CS-OLA-NFs release at the wound site infected with S. aureus for a longer duration of time. Moreover, the PVA-CS-OLA-NFs showed superior wound healing performance against S. aureus infected wounds compared to the marketed formulation. Further, the laser Doppler imaging system improved oxygen saturation, blood supply, and wound healing by providing real-time blood flow and oxygen saturation information.

Flexible transparent ITO thin film with high conductivity and high-temperature resistance

ITO thin films exhibit superior optical characteristics. However, their electrical properties are somewhat less optimal, and they demonstrate limited tolerance under high-temperature conditions. These limitations significantly constrain their potential applications in the domain of optical and electronic devices. In this study, ITO thin films with a thickness of 20 nm were prepared on a flexible Mica substrate. The film has an atomic-level flat surface, high optical transparency (around 85 %), and low resistivity. The stability of the film's surface chemical structure in high-temperature applications was confirmed through XPS characterization. Furthermore, the ITO/Mica flexible thin film demonstrates exceptional durability and recyclability, retaining its optical and electronic properties under a high bending radius of 5 mm and 1000 bending cycles. It is particularly noteworthy that the film's maintenance of good structural and electrical stability (sheet resistance stabilized at 35∼37.5 Ω/sq) under bending cycles at high-temperature (up to 800 °C) conditions, which is crucial for high-temperature resistance in commercial and industrial applications. This study will provide an important experimental basis for the further development and application of ITO thin films in flexible transparent electronic devices with high temperatures and low energy consumption.

Quantitative detection of plasticizer migration in starch/polyvinyl alcohol film with UV-Vis and GC-MS/MS

In this work, the migration of urea and/or formamide plasticizers in crosslinked starch/polyvinyl alcohol (PVA) films under UV irradiation has been accurately quantified by using a combination of GC-MS/MS and UV–Vis analysis. The crosslinked starch/PVA films, prepared with different amide plasticizers (urea, formamide, urea-formamide), were characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and X-ray photoelectron spectroscopy (XPS). After 7 days of UV irradiation, the starch/PVA film plasticized with urea-formamide (A7-SPF-UF) exhibited a flat surface morphology, high crystal stability, and highest thermal stability. The migration ratio of urea and formamide for A7-SPF-UF was also quantified to be 3.2 % and 4.5 %, respectively, using GC-MS/MS and UV–Vis analysis, indicating optimal migration resistance. The synergistic effect of urea and formamide as plasticizers built the dense network structure of An-SPF-UF and improved the UV aging resistance, toughness and durability of the film. On one hand, this enhances the market competitiveness of the products; on the other hand, it promotes the development of environmentally friendly materials, aligning with sustainability requirements.

Optical multiscale model for quantification of photon recycling including incoherent light scattering

A comprehensive multiscale modeling framework for photon recycling in textured solar cells and LEDs is introduced, treating light absorption and emission on an equal footing under consideration of the full internal mode spectrum in the device. The framework seamlessly merges a coherent emission model, free from unphysical divergence and ensuring consistency with detailed balance principles, with an incoherent net-radiation model applied to optically thick layers. The scattering of light at nonplanar interfaces is taken into consideration through four characteristic mappings that depict the microscopic scattering process, which are calculated analytically or by using a Monte-Carlo ray-tracing method. The final output of the model consists of energy- and angle-resolved local emission, re-absorption, and energy flux rates for further coupling to electronic transport. To validate the model, it has been compared with analytical solutions for the re-absorption probability in an ideal semiconductor slab with either ideal Lambertian or flat surfaces. The comparison between analytical and numerical calculations shows excellent agreement.

Assessment of Bond Strength of Different Bonding Systems to Eroded Dentin Using Sonic Activation: In Vitro Study

Abstract Objective Bonding to dentin is a great challenge, and erosion makes it difficult. This study evaluated the effect of sonic agitation on bond strength to eroded dentin using total etch (TE) and self-etch (SE) adhesive systems. Material and Methods A 96-sound human maxillary premolar teeth were prepared to obtain a flat dentin surface, randomly divided into two groups of 48 teeth each. One group was erosive demineralized with 0.05-M citric acid solution to produce an erodedlike dentin surface using de- and remineralization cycles, and the other group was considered a control with no erosive treatment. Each group was bonded with two different bonding strategies, TE (Single Bond 2) and SE (AdheSE One F). Each bonding system was applied with and without sonic activation, and the effect of bond agitation on shear bond strength (SBS) was tested after the application of composite to bonded dentin surface under shear load (0.5 mm/min). Two samples from each group were randomly selected for scanning electron microscopy (SEM) evaluation of the hybrid layer quality. An independent sample t-test was used to assess the effect of erosion, activation, and adhesive type on the SBS. Statistical significance was set at p < 0.05. Result Concerning dentin substrate type, eroded dentin has lower SBS mean values than sound dentin, although it was not significant. Regarding the bonding strategy, TE produced higher SBS values than the SE bonding strategy; it was significant only in sound dentin; despite the bonding strategy and the substrate dentin type, sonic activation produced a significant rise in SBS values except when the SE bonding strategy was applied to eroded dentin where the rise was of no significant value (p > 0.05). Conclusion Sonic agitation effectively improves the SBS value of composite bonded to eroded and sound dentin in both TE and SE strategies.

Frictional Properties of Biomimetic Micro-Hexagonal-Textured Surfaces Interacting with Soft Counterfaces under Dry and Wet Conditions.

Biomimetic micro-hexagonal-textured surfaces have sparked interest for their application in fields that demand high friction and adhesion, such as micro-robotics and biomedicine. Despite extensive research conducted on this specific microstructure, its friction behavior against soft counterfaces remains a topic that has not been fully investigated yet. This study examines how micro-hexagon textures behave when they come into contact with engineered and biological materials like gelatin and chicken skin in dry and wet conditions. The results show clearly that under dry contact conditions, flat surfaces generate higher friction compared to hexagon micropattern surfaces. Under wet conditions, hexagon micropattern surfaces generate higher friction compared to flat surfaces. In wet conditions specifically, the static coefficient of friction is up to 13 times greater than that of a flat specimen against glass, up to 11 times greater against gelatin, and up to 6 times greater against chicken skin. For the dynamic coefficient of friction, the patterned surface demonstrates a maximum increase by a factor of 28 against glass, 11 against gelatin, and 5 against chicken skin. These results further develop our knowledge of these hexagon micropattern surfaces and pave the way for their utilization in future technological advancements in which soft and wet counterfaces are to be considered, such as in biomedical applications that can benefit from increased friction in wet conditions for better control and stability.

Assembling Zn2+ on surface of kevlar NanoFibers as functionalized separator for dendrite-free Zn anode and high-performance Zn metal batteries

The proliferation of wearable electronic products has made the development of flexible energy storage devices increasingly important. Among various options, aqueous Zn metal batteries are promising due to their low cost, safety, non-toxicity, environmental friendliness, and abundant element storage. However, the growth of dendrites on the anode surface of Zn metal batteries is a significant challenge to efficient transport of Zn2+, which leads to reduced battery capacity or even failure. This limitation hinders practical applications for these batteries. This study develops a functionalized separator with high ion transport performance and excellent mechanical performances by electrostatic assembling deprotonated PPTA− molecular chains with Zn2+ using Kevlar as a raw material. The successful assembly of Zn2+ is confirmed through chemical composition and functional group analysis. The prepared separator significantly shows the increased the transfer number of Zn2+ and decreased activation energy of Zn2+ deposition. The separator is used in Zn||Zn symmetric batteries, achieving a reversible deposition/stripping process of more than 180 h at a current density of 1 mA cm−2 and a deposition capacity of 1 mAh·cm−2. When applied to Zn||MnO2 batteries, an initial discharging specific capacity of up to 220 mAh·g−1 is obtained at a high current density of 2 A g−1, and the battery could be cycled stably for more than 1, 200 cycles, with a smooth and flat Zn anode surface and no obvious dendrite growth. The separator has good potential for flexible energy storage applications due to its excellent mechanical strength, which enables it to maintain high electrochemical activity even after bending 500 times at 180°. Overall, the functionalized separator effectively inhibits dendrite growth, improves the electrochemical stability of Zn metal batteries, and demonstrates significant application potential for other flexible energy storage applications.

Origami-Inspired Vacuum-Actuated Foldable Actuator Enabled Biomimetic Worm-like Soft Crawling Robot.

The development of a soft crawling robot (SCR) capable of quick folding and recovery has important application value in the field of biomimetic engineering. This article proposes an origami-inspired vacuum-actuated foldable soft crawling robot (OVFSCR), which is composed of entirely soft foldable mirrored origami actuators with a Kresling crease pattern, and possesses capabilities of realizing multimodal locomotion incorporating crawling, climbing, and turning movements. The OVFSCR is characterized by producing periodically foldable and restorable body deformation, and its asymmetric structural design of low front and high rear hexahedral feet creates a friction difference between the two feet and contact surface to enable unidirectional movement. Combining an actuation control sequence with an asymmetrical structural design, the body deformation and feet in contact with ground can be coordinated to realize quick continuous forward crawling locomotion. Furthermore, an efficient dynamic model is developed to characterize the OVFSCR's motion capability. The robot demonstrates multifunctional characteristics, including crawling on a flat surface at an average speed of 11.9 mm/s, climbing a slope of 3°, carrying a certain payload, navigating inside straight and curved round tubes, removing obstacles, and traversing different media. It is revealed that the OVFSCR can imitate contractile deformation and crawling mode exhibited by soft biological worms. Our study contributes to paving avenues for practical applications in adaptive navigation, exploration, and inspection of soft robots in some uncharted territory.

A Cost-Effective and Easy-to-Fabricate Conductive Velcro Dry Electrode for Durable and High-Performance Biopotential Acquisition.

Compared with the traditional gel electrode, the dry electrode is being taken more seriously in bioelectrical recording because of its easy preparation, long-lasting ability, and reusability. However, the commonly used dry AgCl electrodes and silver cloth electrodes are generally hard to record through hair due to their flat contact surface. Claw electrodes can contact skin through hair on the head and body, but the internal claw structure is relatively hard and causes discomfort after being worn for a few hours. Here, we report a conductive Velcro electrode (CVE) with an elastic hook hair structure, which can collect biopotential through body hair. The elastic hooks greatly reduce discomfort after long-time wearing and can even be worn all day. The CVE electrode is fabricated by one-step immersion in conductive silver paste based on the cost-effective commercial Velcro, forming a uniform and durable conductive coating on a cluster of hook microstructures. The electrode shows excellent properties, including low impedance (15.88 kΩ @ 10 Hz), high signal-to-noise ratio (16.0 dB), strong water resistance, and mechanical resistance. After washing in laundry detergent, the impedance of CVE is still 16% lower than the commercial AgCl electrodes. To verify the mechanical strength and recovery capability, we conducted cyclic compression experiments. The results show that the displacement change of the electrode hook hair after 50 compression cycles was still less than 1%. This electrode provides a universal acquisition scheme, including effective acquisition of different parts of the body with or without hair. Finally, the gesture recognition from electromyography (EMG) by the CVE electrode was applied with accuracy above 90%. The CVE proposed in this study has great potential and promise in various human-machine interface (HMI) applications that employ surface biopotential signals on the body or head with hair.

An Analysis of the Stress–Strain State of a Layer on Two Cylindrical Bearings

A spatial problem of elasticity theory is solved for a layer located on two bearings embedded in it. The bearings are represented as thick-walled pipes embedded in the layer parallel to its boundaries. The pipes are rigidly connected to the layer, and contact-type conditions (normal displacements and tangential stresses) are specified on the insides of the pipes. Stresses are set on the flat surfaces of the layer. The objective of this study is to obtain the stress–strain state of the body of the layer under different geometric characteristics of the model. The solution to the problem is presented in the form of the Lamé equation, whose terms are written in different coordinate systems. The generalized Fourier method is used to transfer the basic solutions between coordinate systems. By satisfying the boundary and conjugation conditions, the problem is reduced to a system of infinite linear algebraic equations of the second kind, to which the reduction method is applied. After finding the unknowns, using the generalized Fourier method, it is possible to find the stress–strain state at any point of the body. The numerical study of the stress state showed high convergence of the approximate solutions to the exact one. The stress–strain state of the composite body was analyzed for different geometric parameters and different pipe materials. The results obtained can be used for the preliminary determination of the geometric parameters of the model and the materials of the joints. The proposed solution method can be used not only to calculate the stress state of bearing joints, but also of bushings (under specified conditions of rigid contact without friction on the internal surfaces).

Coanda Effect Displayed in a Giant Intracranial Aneurysm.

The Coanda effect is a fluid dynamics phenomenon in which a fluid jet adheres to a convex or flat surface. This effect occurs when a liquid or gas jet emerging from an orifice clings to an adjacent surface and entrains the surrounding fluid, creating a lower-pressure region along its path that maintains its attachment to the surface. The Coanda effect accounts for the behavior of blood flow in the fetal right atrium and the dispersion of eccentric mitral regurgitation jets along atrial walls. This series of interesting images depicting a large 4 × 3.75 cm saccular intracranial aneurysm suggests that the Coanda effect may play a role in the pathophysiology of intracranial aneurysms and could be an underlying factor in their formation, progression, or rupture.

Scratch visibility modeling on flat & textured polymeric surfaces

Polymer materials have gained widespread usage in the marketplace due to their lightweight properties, versatility, and cost-effectiveness. However, their susceptibility to scratches has been a longstanding issue. To overcome this shortcoming, surface texturing is one of the most low-cost, efficient ways to improve scratch performance by utilizing the inherent moldability of polymers. Textures rely on both the improvement of contact properties in terms of reduction in surface friction and the perceived visibility of scratches by masking the scratch-induced deformations. The current testing of the effectiveness of a particular texture design on scratch resistance requires tedious and costly psychophysical and/or experimental verification. In this paper, we present a comprehensive framework for scratch visibility analysis in virtual reality, integrating a novel scheme and finite element methods simulation. Our approach considers material, topographical, and optical properties, replicating perceived scratch visibility within the virtual space. The FEM model was found to overpredict the scratch depth and underpredict the shoulder height. A parametric study based on the material constitutive and surface properties has been carried out to highlight the effect of different material and surface factors on scratch performance and visibility. This study opens the door for a complete virtual design-development-analysis cycle for scratch performance evaluation of polymers.

Comparative Morphology of Skeletal Development in Homo sapiens and Raja asterias: Divergent Stiffening Patterns Due to Different Matrix Calcification Processes.

Before calcification begins, the early embryonic and fetal skeletal development of both mammalian Homo sapiens and the chondrichthyan fish Raja asterias consists exclusively of cartilage. This cartilage is formed and shaped through processes involving tissue segmentation and the frequency, distribution, and orientation of chondrocyte mitoses. In the subsequent developmental phase, mineral deposition in the cartilage matrix conditions the development further. The stiffness and structural layout of the mineralized cartilage have a significant impact on the shape of the anlagen (early formative structure of a tissue, a scaffold on which the new bone is formed) and the mechanical properties of the skeletal segments. The fundamental difference between the two studied species lies in how calcified cartilage serves as a scaffold for osteoblasts to deposit bone matrix, which is then remodeled. In contrast, chondrichthyans retain the calcified cartilage as the definitive skeletal structure. This study documents the distinct mineral deposition pattern in the cartilage of the chondrichthyan R. asterias, in which calcification progresses with the formation of focal calcification nuclei or "tesserae". These are arranged on the flat surface of the endo-skeleton (crustal pattern) or aligned in columns (catenated pattern) in the radials of the appendicular skeleton. This anatomical structure is well adapted to meet the mechanical requirements of locomotion in the water column. Conversely, in terrestrial mammals, endochondral ossification (associated with the remodeling of the calcified matrix) provides limb bones with the necessary stiffness to withstand the strong bending and twisting stresses of terrestrial locomotion. In this study, radiographs of marine mammals (reproduced from previously published studies) document how the endochondral ossification in dolphin flippers adapts to the mechanical demands of aquatic locomotion. This adaptation includes the reduction in the length of the stylopodium and zeugopodium and an increase in the number of elements in the autopodium's central rays.

Simulations of Infrared Reflectivity and Transmission Phonon Spectra for Undoped and Doped GeC/Si (001).

Exploring the phonon characteristics of novel group-IV binary XC (X = Si, Ge, Sn) carbides and their polymorphs has recently gained considerable scientific/technological interest as promising alternatives to Si for high-temperature, high-power, optoelectronic, gas-sensing, and photovoltaic applications. Historically, the effects of phonons on materials were considered to be a hindrance. However, modern research has confirmed that the coupling of phonons in solids initiates excitations, causing several impacts on their thermal, dielectric, and electronic properties. These studies have motivated many scientists to design low-dimensional heterostructures and investigate their lattice dynamical properties. Proper simulation/characterization of phonons in XC materials and ultrathin epilayers has been challenging. Achieving the high crystalline quality of heteroepitaxial multilayer films on different substrates with flat surfaces, intra-wafer, and wafer-to-wafer uniformity is not only inspiring but crucial for their use as functional components to boost the performance of different nano-optoelectronic devices. Despite many efforts in growing strained zinc-blende (zb) GeC/Si (001) epifilms, no IR measurements exist to monitor the effects of surface roughness on spectral interference fringes. Here, we emphasize the importance of infrared reflectivity Rω and transmission Tω spectroscopy at near normal θi = 0 and oblique θi ≠ 0 incidence (Berreman effect) for comprehending the phonon characteristics of both undoped and doped GeC/Si (001) epilayers. Methodical simulations of Rω and Tω revealing atypical fringe contrasts in ultrathin GeC/Si are linked to the conducting transition layer and/or surface roughness. This research provided strong perspectives that the Berreman effect can complement Raman scattering spectroscopy for allowing the identification of longitudinal optical ωLO phonons, transverse optical ωTO phonons, and LO-phonon-plasmon coupled ωLPP+ modes, respectively.

Toward the optimization of SiO2 and TiO2-based metamaterials: Morphological, Structural, and Optical characterization

In recent years, metamaterials have emerged as a crucial technology for designing sub-wavelength thick optical components capable of performing various optical functions. Among the others, these nanostructures could be employed to tune the refractive index, making them useful in various fields (from optoelectronic applications to gravitational wave detectors). In this work, nanostratified structures composed of alternating layers of silica (SiO2) and titania (TiO2) were proposed and fabricated using plasma-assisted electron beam deposition. The quality of the deposition was demonstrated using Scanning Transmission Electron Microscopy (STEM), revealing 38 titania/silica doublets with a total thickness compatible with the nominal one of 125.4 nm. X-ray Reflectivity (XRR) and Spectroscopic Ellipsometry (SE) confirmed that the average thicknesses of the titania and silica layers are in good agreement with the expected nominal values even after annealing at 500 °C. Finally, Atomic Force Microscopy (AFM) revealed a very flat surface, both in the as-deposited sample and in the thermally processed one.

Demonstration of β-(Al x Ga1−x )2O3/β-Ga2O3 superlattice growth by mist chemical vapor deposition

This study demonstrates the successful growth of a β-(Al x Ga1−x )2O3/β-Ga2O3 superlattice structure with six periods using mist CVD. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) analysis revealed that the superlattice consisted of six periods of β-(Al x Ga1−x )2O3/β-Ga2O3 with an individual layer thickness of 12.9 nm and 9.1 nm, respectively. XRD analysis further confirmed the periodicity of the structure, yielding a period of 22.7 nm, which is in good agreement with the STEM result. Additionally, the Al composition was determined to be x = 0.085 based on XRD peak positions. Both atomic force microscopy and HAADF-STEM observations revealed atomically flat surfaces and sharp interfaces. This achievement highlights the potential of mist CVD for fabricating complex oxide heterostructures, offering a cost-effective and scalable alternative to conventional methods. The findings open new avenues for developing advanced electronic and optoelectronic devices based on wide-bandgap oxides.

Impact of thick N-polar AlN growth on crystalline quality and electrical properties of N-polar GaN/AlGaN/AlN FET

In this study, we attempted to fabricate N-polar GaN/AlGaN/AlN heterostructure FET by changing the thickness of the AlN layer. An Al-polar tiny-pit AlN layer and a polarity inversion method were used to grow N-polar AlN on vicinal sapphire via the metal-organic vapor phase epitaxy. The samples with an AlN thickness of up to 3.4 μm exhibited a crack-free surface. Additionally, the twist component of the crystal quality improved with an increasing AlN thickness. Consequently, the mobility, sheet conductivity, and surface flatness improved. The FET fabricated from the sample with a thicker AlN layer achieved a higher drain current of 279 mA mm−1 at a gate bias of V G = 3 V.

Overcoming Cancer Persister Cells by Stabilizing the ATF4 Promoter G-quadruplex.

Persister cells (PS) selected for anticancer therapy have been recognized as a significant contributor to the development of treatment-resistant malignancies. It is found that imposing glutamine restriction induces the generation of PS, which paradoxically bestows heightened resistance to glutamine restriction treatment by activating the integrated stress response and initiating thegeneral control nonderepressible 2-activating transcription factor 4-alanine, serine, cysteine-preferring transporter 2 (GCN2-ATF4-ASCT2)axis. Central to this phenomenon is the stress-induced ATF4 translational reprogramming. Unfortunately, directly targeting ATF4 protein has proven to be a formidable challenge because of its flat surface. Nonetheless, a G-quadruplex structure located within the promoter region of ATF4 (ATF4-G4) is uncovered and resolved, which functions as a transcriptional regulator and can be targeted by small molecules. The investigation identifies the natural compound coptisine (COP) as a potent binder that interacts with and stabilizes ATF4-G4. For the first time, the high-resolution structure of the COP-ATF4-G4 complex is determined. The formation of this stable complex disrupts the interaction between transcription factor AP-2 alpha (TFAP2A) and ATF4-G4, resulting in a substantial reduction in intracellular ATF4 levels and the eventual death of cancer cells. These seminal findings underscore the potential of targeting the ATF4-G4 structure to yield significant therapeutic advantages within the realm of persister cancer cells induced by glutamine-restricted therapy.