Coffee Ring Research Articles

Volatile Perovskite Precursor Ink Enables Window Printing of Phase‐Pure FAPbI3 Perovskite Solar Cells and Modules in Ambient Atmosphere

AbstractDespite the great success of perovskite photovoltaics in terms of device efficiency and stability using laboratory‐scale spin‐coating methods, the demand for high‐throughput and cost‐effective solutions remains unresolved and rarely reported because of the complicated nature of perovskite crystallization. In this work, we propose a stable precursor ink design strategy to control the solvent volatilization and perovskite crystallization to enable the wide speed window printing (0.3 to 18.0 m/min) of phase‐pure FAPbI3 perovskite solar cells (pero‐SCs) in ambient atmosphere. The FAPbI3 perovskite precursor ink uses volatile acetonitrile (ACN) as the main solvent with DMF and DMSO as coordination additives is beneficial to improve the ink stability, inhibit the coffee rings, and the complicated intermediate FAPbI3 phases, delivering high‐quality pin‐hole free and phase‐pure FAPbI3 perovskite films with large‐scale uniformity. Ultimately, small‐area FAPbI3 pero‐SCs (0.062 cm2) and large‐area modules (15.64 cm2) achieved remarkable efficiencies of 24.32 % and 21.90 %, respectively, whereas the PCE of the devices can be maintained at 23.76 % when the printing speed increases to 18.0 m/min. Specifically, the unencapsulated device exhibits superior operational stability with T90>1350 h. This work represents a step towards the scalable, cost‐effective manufacturing of perovskite photovoltaics with both high performance and high throughput.

In-Situ Polymer Framework Strategy Enabling Printable and Efficient Perovskite Solar Cells by Mitigating "Coffee Ring" Effect.

Organic-inorganic hybrid perovskites are considered ideal candidates for future photovoltaic applications due to their excellent photovoltaic properties. Although solution-printed manufacturing has shown inherent potential for the low-cost, high-throughput production of thin-film semiconductor electronics, the high-quality and high-reproducibility deposition of large-area perovskite remains a bottleneck that restricts their commercialization due to the droplet coffee-ring effect (CRE). In this study, these issues are addressed by introducing an in situ polymer framework. The 3D framework formed by spontaneous cross-linking improves the precursor viscosity and homogenizes its heat diffusion coefficient, counteracting the lateral capillary flow of the colloidal particles and anchoring their flocculent movement. Thus, the Marangoni convection intensity is properly controlled to ensure high-quality perovskite films, which significantly enhances reproducibility in printing efficient photovoltaics by mitigating the CRE. Subsequently, the perovskite solar cells and modules achieve power conversion efficiencies of 23.94 and 17.53%, and exhibit positive environmental stability, retaining over 90 and 78% efficiency after storage for 2500 and 1600h, respectively. This work may serves as a foundation for exploring precursor rheology to match the homogeneous deposition requirements of perovskite photovoltaics and facilitating the advancement of their printing manufacturing and commercialization transition.

Soft PDMS-mediated formation of bovine serum albumin 3D coffee stain structures for reversible hydrophilic patterning

3D saddle coffee stain is produced when an intermediate-concentration BSA drop evaporates over a soft hydrophobic substrate and deposits a thin protein film enabling reversible hydrophilic patterning.

Electric field-modulated evaporative thin film deposition of bio-particles for piezoelectric applications.

Bio-based functional materials can be used to replace or limit the use of synthetic materials sourced from unsustainable sources. However, the potential of such materials remains largely unexplored. In this study, we demonstrate the use of weak AC electric fields to deposit ultra-thin piezoelectric films from cellulose nanocrystals (CNC). This is the first time electric fields are used to realize <50 nm thick uniform bio-based piezoelectric films wherein the bioparticles exhibit unidirectional arrangement. Interestingly, we found that the use of weak AC electric fields of suitable frequencies completely mitigates the coffee ring effect (CRE), which results in defect-free uniform ultra-thin films. Additionally, the electric fields appear to help in realizing unidirectional alignment of particles in the films, which enhances their piezoelectric properties. The method was also tested for chitin nanocrystals (ChNC), which have a similar aspect ratio but bear opposite polarity surface charges, and the influence of the field on coffee ring formation and particle orientation in CNC thin film deposition was validated. The phenomena can be attributed to the constant spatio-temporal curvature of the evaporating liquid film, the transient state between the three-phase contact (TPC) line, the electric field-dependent contact angle, and the permanent and field-induced dipole moments. These factors lead to particle polarization and alignment. The films have an optimum electrical frequency of deposition at which they are continuous and uniformly thin, have unidirectional alignment of particles, and function as a single dipole.

Analytical applications of droplet deposition Raman spectroscopy.

The droplet deposition methods in Raman spectroscopy have received considerable attention in the field of analytical sensing focusing on effective pre-concentration of the studied analyte (coffee-ring effect or small spots). This review covers different analytical applications of drop-coating deposition Raman scattering (DCDRS) and droplet deposition surface-enhanced Raman scattering (SERS) spectroscopy. Two main advantages of droplet deposition Raman techniques are considered: the drying-induced segregation of the components from the mixtures (such as body fluids) and the sensitivity of detection of various analytically important molecules. Some recent advanced applications, including clinical cancer diagnosis, are discussed and summarized. Finally, the potential and further perspectives of the droplet deposition Raman methods for analytical studies are introduced.

The role of autophagy in SIM mediated anti-inflammatory osteoclastogenesis through NLRP3 signaling pathway.

Inflammatory bone resorption is a prominent risk factor for implantation failure. Simvastatin (SIM) has anti-inflammatory effects independent of cholesterol lowering and reduces osteoclastogenesis by decreasing both the number and activity of osteoclasts. However, the specific mechanism of inflammatory bone loss alleviation by SIM remains to be elucidated. We hypothesized that SIM relieves inflammatory bone loss by modulating autophagy and suppressing the NOD-like receptor family pyrin domain-containing protein 3 (NLRP3) signaling pathway. RAW264.7 cells were stimulated by lipopolysaccharide (LPS) after being pretreated with various concentrations of SIM. Osteoclast (OC) differentiation, formation and activity were evaluated by tartrate-resistant acid phosphatase staining, F-actin ring staining and bone resorption pit assays, respectively. We observed autophagosomes by transmission electron microscopy. Then NLRP3 inhibitor MCC950 was used to further explore the corresponding molecular mechanism underlying anti-inflammatory bone resorption, the expression of autophagy-related proteins and NLRP3 signaling pathway factors in pre-OCs were evaluated by western blot analysis, and the expression of OC-specific molecules was analyzed using reverse transcription-quantitative polymerase chain reaction. The results showed that SIM decreased the expression of tumor necrosis factor-α, whereas increased Interleukin-10. In addition, SIM inhibited LPS-induced OC differentiation, formation, bone resorption activity, the level of autophagosomes, and OC-specific markers. Furthermore, SIM significantly suppressed autophagy by downregulating LC3II, Beclin1, ATG7, and NLRP3-related proteins expression while upregulating P62 under inflammatory conditions. SIM may reduce autophagy secretion to attenuate LPS-induced osteoclastogenesis and the NLRP3 signaling pathway participates in this process, thus providing theoretical basis for the application of this drug in peri-implantitis.

Inkjet printing high mobility indium-zinc-tin oxide thin film transistor

Metal oxide thin film transistor has been widely used in flat panel display industry because of its low leakage current, high mobility and large area uniformity. Besides, with the development of printed display technology, inkjet printing process can fabricate the customizable patterns on diverse substrates with no need of vacuum or lithography to be used, thus significantly reducing cost and receiving more and more attention. In this paper, we use inkjet printing technology to prepare a bottom gate bottom contact thin film transistor (TFT) by using indium-zinc-tin-oxide (IZTO) semiconductor. The surface morphology of the printed IZTO film is modified by adjusting the solvent composition and solute concentration of the printing precursor ink. The experimental result show that the use of binary solvents can effectively overcome the coffee ring shape caused by the accumulation of solute edge in the volatilization process of a single solvent, ultimately presenting a uniform and flat contour surface. Further increase in solute concentration is in favor of formation of convex surface topology. The reason for the formation of the flat surface of the oxide film is the balance between the inward Marangoni reflux of the solute and the outward capillary flow during volatilization. In addition, IZTO thin film transistor printed with binary solvents exhibits excellent electrical properties. The ratio of width/length = 50/30 exhibits a high on-off ratio of 1.21×10&lt;sup&gt;9&lt;/sup&gt;, a high saturation field-effect mobility is 16.6 cm&lt;sup&gt;2&lt;/sup&gt;/(V·s), a low threshold voltage is 0.84 V, and subthreshold swing is 0.24 V/dec. The uniform and flat active layer thin film pattern can form good contact with the source leakage electrode, and the contact resistances of TFT devices with different width-to-length ratios are less than 1000 Ω, which can reach the basic conditions of high mobility thin film transistors prepared by inkjet printing. Therefore, using solvent mixture provides a universal and simple way to print oxide films with required surface topology, and present a visible path for inkjet printing of high-mobility thin film transistors.

Evaluating Ink Structure Using Ultrasonic Spray Coating for PEMFC MEA

From the standpoint of improving manufacturing productivity and performance/durability of PEMFC MEAs, there is an increasing interest in ink. Ink research is centered on comprehending the interplay between the components of the ink, including catalysts, ionomers, and solvents, to control the ink structure and evaluate its influence on ink properties, catalyst layer microstructure, and fuel cell performance. As a facet of this ink research, the current study proposes ultrasonic spray coating as a methodology to indirectly evaluate the ink structure.50 wt% Pt/C catalysts loaded on Ketjenblack (KB) and Vulcan carbon (VC) were separately incorporated to produce sprayable inks with a solid content of 4 wt% using an Aquivion ionomer (EW 720) and a mixture solvent composed of a 1:1 weight ratio of 1-propanol and water. The structural differences between the two catalyst inks were compared by quantifying the amount of adsorbed and free ionomers, as well as their rheological properties. Additionally, the advantages of ultrasonic spray coating, such as the formation of small droplets on the order of tens of micrometers and rapid drying, were utilized to coat each ink onto a silicon substrate. The structural characteristics of the resulting catalyst layers were compared through SEM images, as well as the distribution of constituent elements using EDS and Auger spectroscopy. The Pt/KB catalyst ink forms a gel-like structure due to its relatively high amount of adsorbed ionomer, resulting in a relatively uniform distribution of catalyst particles and ionomers in the catalyst layer formed from ultrasonic spray droplets. In contrast, the Pt/VC catalyst ink behaves as a liquid-like, mainly existing in the form of free ionomer, regardless of ionomer content. During the drying process of each droplet, they merge to form larger unit catalyst layers, which exhibit an uneven distribution where free ionomers tend to concentrate at the edges of the catalyst layer due to the coffee-ring effect. As a result, the catalyst and ionomers exist in a non-uniform distribution, which is observed to affect the performance and electrochemical characteristics of fuel cells. In this presentation, we will discuss in detail the series of characteristics of ink-catalyst layer-fuel cell performance that vary according to catalyst properties.

An ultra-stable and sensitive Ag-HP-β-CD/GO/NCF SERS substrate combine with the coffee-ring effect strategy for trace PAHs detection

This study proposes an ultra-stable and highly sensitive SERS substrate based on Ag nanoparticles/graphene oxide nanosheets hybrids decorated nanocellulose fiber (Ag/GO/NCF), which was further functionalized with hydroxypropyl-β-cyclodextrin (Ag-HP-β-CD/GO/NCF) for the trace detection of polycyclic aromatic hydrocarbons (PAHs). The Ag/GO hybrid structure enables the substrate to exhibit high SERS activity through the synergistic effect of electromagnetic and chemical enhancement. Simultaneously, the three-dimensional skeleton structure of NCF serves as a support matrix, ensuring the exceptional stability of the substrate. Furthermore, this study introduces a SERS measurement strategy utilizing the coffee-ring effect and explores parameters optimization to further enhance the detection sensitivity while maintaining the homogeneity and reproducibility. With the affinity effect of HP-β-CD and the enrichment effect of the delocalized π-electron system in GO, the hydrophobic PAHs could easily approach the SERS hotspots and achieve their trace detection. The limit of detection (LOD) for four representative PAHs, including pyrene, fluoranthene, phenanthrene and fluorene, are found to be 3.32 ug/L, 3.65 ug/L, 40.97 ug/L and 56.24 ug/L, respectively. These results highlight the potential application of this highly efficient SERS platform in environmental monitoring.

Plasmonic metasurfaces of cellulose nanocrystal matrices with quadrants of aligned gold nanorods for photothermal anti-icing

Cellulose nanocrystals (CNCs) are intriguing as a matrix for plasmonic metasurfaces made of gold nanorods (GNRs) because of their distinctive properties, including renewability, biodegradability, non-toxicity, and low cost. Nevertheless, it is very difficult to precisely regulate the positioning and orientation of CNCs on the substrate in a consistent pattern. In this study, CNCs and GNRs, which exhibit tunable optical and anti-icing capabilities, are employed to manufacture a uniform plasmonic metasurface using a drop-casting technique. Two physical phenomena—(i) spontaneous and rapid self-dewetting and (ii) evaporation-induced self-assembly—are used to accomplish this. Additionally, we improve the CNC-GNR ink composition and determine the crucial coating parameters necessary to balance the two physical mechanisms in order to produce thin films without coffee rings. The final homogeneous CNC-GNR film has consistent annular ring patterns with plasmonic quadrant hues that are properly aligned, which enhances plasmonic photothermal effects. The CNC-GNR multi-array platform offers above-zero temperatures on a substrate that is subcooled below the freezing point. The current study presents a physicochemical approach for functional nanomaterial-based CNC control.

Large-Area Flexible Perovskite Light-Emitting Diodes Enabled by Inkjet Printing.

Metal halide perovskite light-emitting diodes (PeLEDs) are attracting increasing attention due to their potential applications in flat panel lighting and displays. The solution process, large-area fabrication, and flexibility are attractive properties of PeLEDs over traditional inorganic LEDs. However, it is still very challenging to deposit uniform perovskite films on flexible substrates using a blade or slot-die coating, as the flexible substrate is not perfectly flat. Here, the inkjet printing technique is adopted, and the key challenges are overcome step-by-step in preparing large-area films on flexible substrates. Double-hole transporting layers are first used and a wetting interfacial layer to improve the surface wettability so that the printed perovskite droplets can form a continuous wet film. The fluidic and evaporation dynamics of the perovskite wet layer is manipulated to suppress the coffee ring effect by solvent engineering. Uniform perovskite films are obtained finally on flexible substrates with different perovskite compositions. The peak external quantum efficiency of the inkjet-printed PeLEDs reaches 14.3%. Large-area flexible PeLEDs (4×7 cm2 ) also show very uniform emission. This work represents a significant step toward real applications of large-area PeLEDs in flexible flat-panel lighting.

Controlling the Nucleation and Growth of Salt from Bodily Fluid for Enhanced Biosensing Applications.

Surface-enhanced Raman spectroscopy (SERS) represents a transformative tool in medical diagnostics, particularly for the early detection of key biomarkers such as small extracellular vesicles (sEVs). Its unparalleled sensitivity and compatibility with intricate biological samples make it an ideal candidate for revolutionizing noninvasive diagnostic methods. However, a significant challenge that mars its efficacy is the throughput limitation, primarily anchored in the prerequisite of hotspot and sEV colocalization within a minuscule range. This paper delves deep into this issue, introducing a never-attempted-before approach which harnesses the principles of crystallization-nucleation and growth. By synergistically coupling lasers with plasmonic resonances, we navigate the challenges associated with the analyte droplet drying method and the notorious coffee ring effect. Our method, rooted in a profound understanding of crystallization's materials science, exhibits the potential to significantly increase the areal density of accessible plasmonic hotspots and efficiently guide exosomes to defined regions. In doing so, we not only overcome the throughput challenge but also promise a paradigm shift in the arena of minimally invasive biosensing, ushering in advanced diagnostic capabilities for life-threatening diseases.

Isoquercitrin attenuates the osteoclast-mediated bone loss in rheumatoid arthritis via the Nrf2/ROS/NF-κB pathway

An excess of osteoclastogenesis significantly contributes to the development of rheumatoid arthritis (RA). Activation of the nuclear factor erythroid-2 related factor 2 (Nrf2) and nuclear factor kappa B (NF-κB) ligand (RANKL)-induced reactive oxygen species (ROS)-to-NF-κB signaling cascade are important mechanisms regulating osteoclastogenesis; however, whether Nrf2 is involved in RANKL-induced NF-κB activation is controversial. Isoquercitrin, a natural flavonoid compound, has been shown to have Nrf2-dependent antioxidant effects inprevious studies. We sought to verify whether isoquercitrin could modulate RANKL-induced NF-κB activation by activating Nrf2, thereby affecting osteoclastogenesis. Tartrate-resistant acid phosphatase staining, F-actin ring staining and resorption pit assay suggested that isoquercitrin significantly inhibited osteoclastogenesis and osteolytic function. Mitosox staining showed that RANKL-induced ROS generation was significantly inhibited by isoquercitrin from day 3 of the osteoclast differentiation cycle. Quantitative real-time PCR, Western blot, and immunofluorescence indicated that isoquercitrin activated the Nrf2 signaling pathway and inhibited NF-κB expression. And when we used the Nrf2-specific inhibitor ML385, the inhibition of NF-κB by isoquercitrin disappeared. Moreover, we found that Nrf2 is not uninvolved in RANKL-induced NF-κB activation and may be related to the timing of ROS regulation. When we limited isoquercitrin administration to 2 days, Nrf2 remained activated and the inhibition of NF-κB disappeared. In vivo experiments suggested that isoquercitrin attenuated RA modeling-induced bone loss. Overall, isoquercitrin-activated Nrf2 blocked the RANKL-induced ROS-to-NF-κB signaling cascade response, thereby inhibiting osteoclastogenesis and bone loss. These findings provide new ideas for the treatment of RA.

Simultaneously Suppressing the Coffee Ring Effect of Solutes with Different Sizes.

Suppressing the coffee ring effect (CRE), which improves the uniformity of deposition, has attracted great attention. Usually, a realistic system contains solutes of various sizes. Large particles preferentially settle onto the substrate under gravity, separated from small particles even when CRE is suppressed, which generates nonuniformity in another way. This hinders small particles from filling the gaps at the deposition-substrate interface, leaving a frail deposition. Here, the CRE of polydispersed solutes is simultaneously suppressed, and a more uniform deposition is achieved by suspending the drop together with adding trace amounts of cations. The gaps tend to be filled, which makes the deposition bind more tightly. Analysis shows that gravity coordinates with the interactions that mediate the attraction between particles and the substrate, resulting in the coinstantaneous adsorption of all particles. This work adds another dimension to the suppression of CRE, improving the uniformity of deposition in complex systems and paving the way for the development of techniques in diverse manufacturing industries.

Synthesis of tailored nanostructured gold surfaces for SERS applications by controlled seed deposition and growth

Surface-enhanced Raman spectroscopy (SERS) sensors are commonly based on metal nanoparticles in colloidal suspension followed by deposition on a substrate. Despite its simplicity, this approach leads to non-uniform SERS substrates that are hampered by features such as coffee rings. Seed-mediated growth starting from nanoparticles already deposited on a flat substrate potentially allows for creating more uniform and reliable sensors. However, the deposition process, the control of the distribution of the seed nanoparticles, and their optimal growth have not been thoroughly explored. In this work, we present a systematic approach to designing and fabricating gold nanostructured surfaces, tailoring their SERS responses on demand. By controlling and tuning the deposition of nanoparticles, assisted by an experimental and theoretical investigation, we achieved good control over the spatial distribution of the deposited seeds. After enlarging such seeds through chemical reduction, the optimized SERS substrates show great uniformity in their hotspots, a critical feature for sensors. The so-fabricated substrates were used for detecting Skatole in water, achieving a detection limit of 42.2 ppt. The developed methodology has significant implications for the advancement of several fields, particularly SERS-based sensing, enabling the design and targeting of specific excitation wavelengths and Raman bands while obtaining uniform and reliable substrates.

Biomimetic Surface Engineering to Modulate the Coffee-Ring Effect for Amyloid-β Detection in Rat Brains.

Surface engineering of nanoparticles has been widely used in biosensing and assays, where sensitivity was mainly limited by plasmonic colour change or electrochemical responses. Here, we report a novel biomimetic sensing strategy involving protein-modified gold nanoparticles (AuNPs), where the modulation strategy was inspired by gastropods in inhibition of coffee-ring effects in their trail-followings. The so-called coffee-ring effect presents the molecular behaviour of AuNPs to a macroscopic ring through aggregation, and thus greatly improves sensitivity. The assay relies upon the different assembly patterns of AuNPs against analytes, resulting in the formation or suppression of coffee-ring effects by the different surface engineering of AuNPs by proteins and peptides. The mechanism of the coffee-ring formation process is examined through experimental characterizations and computational simulations. A practical coffee-ring effect assay is developed for a proof-of-concept target, amyloid β (1-42), which is a typical biomarker of Alzheimer's disease. A novel quasi-titrimetric protocol is constructed for quantitative determination of the target molecule. The assay shows excellent selectivity and sensitivity for the amyloid β monomer, with a low detection limit of 20 pM. Combined with a fluorescent staining technique, the assay is designed as a smart sensor for amyloid β detection and fibrillation evaluation in rat cerebrospinal fluids, which is a potential point-of-care test for Alzheimer's disease. Connections between amyloid fibrillation and different courses of brain ischaemia are also studied, with improved sensitivity, lower sample volumes that are required, convenience for rapid detection, and point-of-care testing.

A numerical model for the transport and drying of solutions in thin porous media — Coffee-stain effect and solute ring formation

We have developed a comprehensive numerical model for the transport and drying of solutions in thin porous media that consist of permeable fibers such as paper. We explicitly account for the gas-phase transport dynamics. Moreover, we introduce an empirical relation for the concentration- and molecular-weight dependence of the pore-fiber transport rate of the solutes. These two key elements enable us for the first time to realistically model two important phenomena relevant to inkjet printing technology. The first is the equivalent of the coffee-stain effect for dilute solutions in porous media. The second is the formation of solute rings for concentrated aqueous mixtures of compounds with a molecular weight significantly above that of water. Whereas the first is governed by spatially non-uniform solvent evaporation, the second case is dominated by solvent-mediated pore-fiber transport. We achieved a good qualitative agreement with the available experimental data.

Research on water heavy metal element detection using surface-enhanced LIBS based on coffee ring enrichment

In order to enhance the stability and lower the detection limit of Laser-Induced Breakdown Spectroscopy (LIBS) technology, gelatin was introduced into the test solution in this study to enrich heavy metals using the coffee ring effect. The effects of different gelatin mass fractions on the surface deposition morphology of droplets and the intensity of spectroscopy were analyzed. Explored the spectral enhancement mechanisms of four substrate materials. The results demonstrated that the best coffee ring enrichment was achieved with a gelatin mass fraction of 2.5 %. The signal-to-noise ratios of Cu and Cr were enhanced by 5.5 and 3.6, and the relative standard deviations decreased by 59.5 % and 53.8 %. When Zn plate was used as the substrate material, the detection limits for Cu and Cr were 0.715 mg/L and 3.881 mg/L. The research indicates that surface-enhanced LIBS based on coffee ring enrichment can improve spectral stability and lower the detection limit.

Bifurcation and Transposition of the Wicking Front of Binary Solutions Infiltrating into Chromatography Paper Associated with Their Evaporation.

Nonequilibrium fluid patterns, such as Marangoni contraction, coffee rings, and tears of wine, are generated in binary solutions spread on a substrate during their evaporation. In this study, we observed another type of nonequilibrium behavior exhibited by binary solutions as they infiltrate porous materials and undergo evaporation. A binary solution comprising hexane and ethanol was brought into contact with the chromatography paper to facilitate infiltration into the paper's pores. Because the experimental setup was in an open environment, infiltration and evaporation occurred simultaneously. The wicking front exhibited an initial rapid advancement, followed by subsequent receding and readvancing. Additionally, the bifurcation of the wicking front after the onset of its readvancement was confirmed by monitoring the temporal evolution of the spatial luminance distribution and temperature distribution on the surface of the chromatography paper. Chromatographic development of a hydrophilic dye was conducted in this experimental setup in an open environment. Additionally, it was confirmed that the receding and readvancing of the wicking front represented the transposition of the bifurcated wicking fronts.

Taming the coffee-ring effect on solid surface by localized heating upon the suspension droplet

Coffee-ring effect is a very common phenomenon in our daily life, especially in the evaporation process of colloidal solutions on solid surfaces. However, in processes such as inkjet printing, this effect can change the uniformity of the deposited film, thus affecting the quality of the printed products. In this paper, a facile and convenient method of localized heating of liquid droplets by using a tiny steel wire is proposed. The results indicated that this method can effectively suppress the generation of coffee-ring effect, and the deposition morphology of the suspended particles can be adjusted by controlling the applied temperature, wire diameter and the distance from the wire to the droplet. And it was found that the heated wire-induced inward flows caused by the temperature gradient of the droplet are the main reason for adjusting the deposition morphology. The coffee-ring effect is mainly controlled by the free convection from the edge to the center caused by the evaporation loss of the solution, so as to adjust the distribution of suspended particles in the evaporating droplet and thus achieve the goal of suppressing the coffee-ring effect. This method has no special requirements for the substrate and droplet solution, and it is expected to be universally applicable to uniform deposition of colloidal solutions.