Greater Surface Roughness Research Articles

Effect of Er doping on the ammonia sensing properties of ZnO thin films prepared by a nebulizer spray technique

Erbium (Er)-doped ZnO thin films were deposited on glass substrates by nebulizer spray pyrolysis with different doping concentrations (0 wt%, 1 wt%, 3 wt% and 5 wt%). The deposited films are polycrystalline with a hexagonal structure with a (002) predominant plane. The Er-doped ZnO films have greater surface roughness than the undoped ZnO film. The optical transmittance of the undoped ZnO film is about 80% in the visible range. The optical bandgap of the undoped ZnO thin film is 3.29 eV, which is very close to the bulk ZnO. From photoluminescence spectra, sharp UV emission is observed at 385 nm for all the prepared films. The response of the films to ammonia (NH3) vapour is high when the Er concentration is 3% or less, and for higher concentrations of Er, the response is low. All the deposited Er-doped ZnO films show short response time and recovery time with regard to NH3.

Effect of titanium surface topography on plasma deposition of antibacterial polymer coatings

Plasma processing, e.g., functionalisation and deposition of antibacterial coatings, is often used to enhance surface properties of biomaterials. Plasma is, however, a non-uniform active medium, and the result of processing depends on the nature of both the plasma and the substratum. Here we show that when an antibacterial coating (i.e., polyterpenol) is plasma polymerised onto four types of titanium substrata that differ in their micro- and nano-scale topography (but not the bulk chemistry), the distribution of functional groups, e.g., OH and CO, in the polymer across the surface differs sufficiently, and so does the antibacterial activity of the resulting material system. While the addition of a coating hinders biofilm formation by Staphylococcus aureus and Pseudomonas aeruginosa, the bactericidal effect is significantly stronger in polymers deposited onto surfaces possessing lower degrees of nanoscale roughness, e.g., substrata after mechanical and chemical polishing. The reduced antibacterial efficacy of polymers on substrata with greater surface roughness (e.g., on mechanically polished or lotus leaf-like surfaces) is attributed to a greater extent of thickness non-uniformity and heterogeneity in the functional group distribution across the surface. These findings suggest that the magnitude and distribution of topographical features of the substratum should be considered when designing plasma-enabled surface modification strategies.

Cooling of porous metal surfaces by droplet impact

An experimental study was conducted on the impact of droplets of pure water and n-heptane on impervious and porous (5 µm and 100 µm pore size) stainless steel surfaces. Surface porosity, roughness and thermal conductivity were measured. Droplet diameter (2.5 mm) and impact velocity (0.9 m/s) were kept constant while surface temperature was varied from room temperature to 300 °C. Droplet impact was observed using a high-speed video camera. Droplet evaporation times were measured by recording the change in weight of the surface on which the droplet was deposited and surface temperature variation during droplet impact measured using a fast response surface thermocouple.Droplets spread out on porous surfaces during impact to form a thin film that was then drawn into pores by capillary forces. The rate of droplet spread decreased with greater surface roughness. The Leidenfrost temperature of n-heptane droplets increased with surface porosity while water droplets did not go into film boiling on the porous surfaces. A one-dimensional heat conduction model was used to estimate heat transfer coefficients between the impacting droplets and substrates. Heat transfer coefficients increased with surface temperature until sufficient vapor was generated at the liquid-solid interface to inhibit contact. Heat transfer coefficients then decreased with further increases in temperature.

Fabrication of LaFeO3 and rGO-LaFeO3 microspheres based gas sensors for detection of NO2 and CO.

In the present report, gas sensing devices based on LaFeO3 and rGO-LaFeO3 were fabricated by a photolithography technique. The X-ray diffraction, Raman spectra and FT-IR results confirm the formation of a perovskite phase and composite. XPS and TEM give the chemical compositions for both products. The higher roughness, greater surface area (62.1 m2 g−1), larger pore size (16.4 nm) and lower band gap (1.94 eV) of rGO-LaFeO3 make it a suitable candidate to obtain high sensitivity. The gas sensing performance of the devices was investigated for various concentrations of NO2 and CO gases at temperatures of 200 and 250 °C. It was observed that the rGO-LaFeO3 based device exhibited a high relative response (183.4%) for a 3 ppm concentration of NO2 at a 250 °C operating temperature. This higher response is attributed to the large surface area, greater surface roughness, and numerous active sites of rGO-LaFeO3. The gas sensing properties investigated show that rGO-LaFeO3 is an excellent candidate for an NO2 sensor.

The comparison of shear bond strength of metal orthodontics bracket to porcelain surface using silane and single bond: An in vitro study

Aim: To investigate the dissimilarity of the shear bond strength of bracket on porcelain surface using silane and single bond. Materials and Methods: This study was laboratory experimental research with posttest-only group design. Simple random sampling was performed to select the sample. Twenty-eight porcelain veneers were used as sample, then divided into four groups accordingly: hydrofluoric acid, silane, bonding, and adhesive (I); hydrofluoric acid, single bond, bonding, and adhesive (II); hydrofluoric acid, bonding, and adhesive (III); and single bond and adhesive (IV). Shear bond strength of brackets was performed by means of universal testing machine. Scanning electron microscope was used to examine the porcelain surface roughness. Wilcoxon Mann–Whitney test (P < 0.05) was performed to analyze the difference between groups. Result: The shear bond strengths between groups were significantly different (P < 0.05). The greatest bracket shear bond strength and lowest porcelain surface roughness were found in hydrofluoric acid, silane, bonding, and adhesive. Conclusion: Silane applied separately from bonding and acid has great shear bond strength and low porcelain surface roughness.

Induced biological soil crust controls on wind erodibility and dust (PM10) emissions

ABSTRACTInducing biological soil crust (biocrust) development is an appealing approach for dust mitigation in drylands due to the resistance biocrusts can provide against erosion. Using a portable device, we evaluated dust emissions from surfaces either inoculated with biocrust, amended with a plant‐based soil stabilizer, or both at varying wind friction velocities. Four months after application, emissions from all treatments were either indistinguishable from or greater than controls, despite evidence of biocrust establishment. All treatments had greater surface roughness and showed more evidence of entrapment of windblown sediment than controls, factors which may have been partially responsible for elevated emissions. There was a synergistic effect of inoculation and stabilizer addition, resulting in a nearly two‐fold reduction in estimated emissions compared to either treatment alone. Stepwise regression analysis indicated that variables associated with surface crust strength (aggregate stability, penetration resistance) were negatively associated with emissions and variables associated with sediment supply (sand content, loose sediment cover) were positively associated with emissions. With more time to develop, the soil‐trapping activity and surface integrity of biocrust inoculum and soil stabilizer mixtures is expected to increase with the accumulation of surface biomass and enhancement of roughness through freeze–thaw cycles. © 2019 John Wiley &amp; Sons, Ltd.

Effects of demineralization on the surface morphology, microcrystalline and thermal transformation characteristics of coal

In this study, experiments were conducted to systematically determine how the surface morphology, microcrystalline and thermal transformation characteristics of coal change during acid treatment. HCl-HF acid washing was applied to pretreat the raw coal. The effects of the demineralization treatment on the carbonaceous structure and functional groups were first tested using X-ray diffraction (XRD), Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). The results show that the demineralization treatment significantly removes the peaks of inherent mineral matter (based on XRD), enhances the disorder in the structure of the coal (based on Raman spectroscopy), and changes the structure of CO, the aromatic structure and the aliphatic side chains (based on FTIR). The surface morphologies of the raw coal and demineralized coal were then studied by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The results show that the demineralized coal has a greater surface roughness than the raw coal. The surface morphology of the macerals show that the demineralization treatment transforms the vitrinite peaks to valleys and increases the depths of the valleys; furthermore, the demineralization treatment cause the peaks and valleys of the surface roughness to interchange. Finally, pyrolysis experiments of the raw coal and demineralized coal were conducted with thermogravimetric analysis (TGA) and a fixed-bed reactor, and the subsequent gas and tar compositions were characterized by gas chromatography (GC) and gas chromatography–mass spectrometry (GCMS). The results show that the pyrolysis reactivity of coal is decreased by demineralization treatment. The pyrolysis experiments in the fixed-bed reactor indicate that the pyrolysis conversion rate increases with the base-acid ratio of the inherent mineral matter. The pyrolysis products show that the amounts of H2 and CH4 increases due to the presence of the inherent mineral matter. The inherent mineral matter can also promote the cracking of aliphatic hydrocarbons, polycyclic aromatic hydrocarbons and oxygen-containing compounds in the pyrolysis tar.

Effect of acidic pH on surface roughness of esthetic dental materials

Statement of problemExposure to gastric acid in patients with bulimia nervosa and gastroesophageal reflux disease (GERD) causes demineralization of hard tooth structures. This chemical attack also causes the degradation of dental ceramics, which results in increased surface roughness and reduced strength. However, studies comparing the effect of acidic pH on resin matrix ceramic with other computer-aided design and computer-aided manufacturing (CAD-CAM) esthetic materials are lacking. PurposeThe purpose of this in vitro study was to compare the surface roughness changes of different CAD-CAM restorative dental materials after exposure to acidic pH by using a 3D optical interferometer. Material and methodsFive esthetic CAD-CAM block materials, a leucite glass-ceramic (IPS Empress CAD), a zirconia (BruxZir Solid Zirconia), a resin matrix ceramic (VITA Enamic), a lithium disilicate glass-ceramic (IPS e.max CAD), and a feldspathic porcelain (VITABLOCS Mark II CAD) were tested. Eighteen specimens were sectioned from CAD-CAM blocks into 2-mm-thick rectangular plates and immersed in 10 mL of 5% hydrochloric acid (HCl) with (pH=2) at 37 °C for 45 and 91 hours. The surface roughness average (Ra) of the specimens was measured by using a 3D optical interferometer before the storage period (baseline), after 45 hours, and after 91 hours of exposure to HCl. Statistical analyses were performed with the Kruskal-Wallis test and the post hoc Dunn test with Bonferroni correction (α=.05). ResultsRegarding the comparison of surface roughness changes at different periods of evaluation (baseline, 45 hours, 91 hours), there were no statistically significant differences for lithium disilicate (P=.063) or zirconia (P=.513). Leucite glass-ceramic, feldspathic porcelain, and the resin matrix ceramic demonstrated statistically significant differences (P<.001). For all tests that were statistically significant, greater surface roughness was found at the time point with the longer HCl exposure. Regarding the comparison of materials in terms of change in surface roughness between baseline to 45 hours and baseline to 91 hours, the Kruskal-Wallis test indicated a statistically significant difference among the materials in both cases (P<.001). Lithium disilicate and zirconia exhibited the least change in surface roughness among the 5 materials. ConclusionsLeucite glass-ceramic, feldspathic porcelain, and resin matrix ceramic showed statistically significant increases in surface roughness when they were exposed to simulated gastric acid for 45 and 91 hours. Lithium disilicate and zirconia showed no statistically significant change in surface roughness after exposure to HCl for 45 and 91 hours.

Development and Preliminary Evaluation of a System to Rapidly Measure Coefficient of Friction on Soft Contact Lenses

This study was undertaken to 1. develop an apparatus to rapidly measure coefficient of friction (COF) on soft contact lenses; 2. determine if COFs measured on two daily-disposable lens models before and after wear are consistent with changes in lens surface morphology observed in parallel atomic force microscopy (AFM) images. Methods: A stress rheometer was adapted to measure COF on a soft contact lens by custom fabrication of a rapid-mount sample stage for increased throughput. Five subjects were randomly assigned to wear daily disposable nesofilcon A and delefilcon A contact lenses bilaterally for 4 hours, after which time lenses were removed. Static and kinetic COFs of lenses worn on left eyes was measured, while lenses worn on right eyes were imaged in parallel by AFM in tapping mode. Root mean square (RMS) surface roughness was calculated for all lenses to determine the effect of wear on surface topography. Results: Both static and kinetic COFs measured on unworn delefilcon A silicone hydrogel lenses were greater than on nesofilcon A traditional hydrogel lenses. Static COF on nesofilcon A increased significantly after wear, while kinetic COF trended higher but did not change significantly. Similarly, static COF on delefilcon A also increased significantly after wear, and kinetic COF trended higher but did not change significantly, both remaining greater than on worn nesofilcon A. Parallel AFM analysis demonstrated that nesofilcon A lenses are smoother than are delefilcon A out of the package. Both lenses attracted deposits during wear, but the nesofilcon A surface was less altered by on-eye wear than was the delefilcon A surface. Conclusion: A system to rapidly measure static and kinetic COFs was successfully developed. Static and kinetic COFs measured on delefilcon A were greater than on nesofilcon A lenses. More deposits and greater surface roughness were observed after wear on delefilcon A relative to nesofilcon A. Parallel AFM images of worn and unworn lenses were not predictive of measured COFs, but increased roughness visible by AFM was consistent with observed increases in COF, although not all increases were statistically significant.

High‐speed photography of water drop impacts on sand and soil

SummaryThe way that water drops impact on soil is of widespread importance for soil science, particularly in the context of irrigation and erosion. With modern high‐speed photography techniques, impacts on granular materials are becoming more widely studied, but the variation in particle‐size distribution of soil presents particular challenges. Here, the impacts of individual water drops on two contrasting soil textures (pure sand and a loamy soil) have been studied with high‐speed photography, and compared at Weber numbers between 50 and 750. Granular samples with wider distributions of particle sizes produce larger variations in experimental outcomes. For the sand, which contained &gt;98% particles between 60 μm and 2 mm in size, the typical outcome involved spreading and retraction of the drop to a circular profile with a raised rim. The loamy soil had greater surface roughness than the sand, with a wider distribution of particle sizes, so that the spread of the drop was more anisotropic, involved more movement of target particles and often involved droplet breakup into satellite drops. Overall outcomes were best described by a gravity‐dominated cratering mechanism, and the scaling exponent for the crater diameter with respect to impact energy was 0.22 ± 0.03. Dynamic penetration studies enabled visualization of granular motion below the surface, and both static and dynamic penetration results illustrated a transition between inertial and viscous regimes over time. As the water content of the soil was increased, droplet breakup was initially encouraged before capillary imbibition dominated at water contents close to 10%v/v. This research is useful for understanding how rain and irrigation, which comprise many millimetre‐scale drops, influence large‐scale hydraulic properties in soil, including surface sealing.Highlights Drop impact on to soil is important, but its systematic study is difficult because of variation in soil particle sizes. High‐speed photography was used to study drop impacts on to a pure sand and loamy soil, and analysed quantitatively. Results show how granular samples with wider distributions of particle sizes produce more variation in experimental outcomes. The maximum extent of drop spreading was best described by a scaling model developed for planetary cratering.

Anodizing of Ti6Al4V alloy for aeronautical applications

The anodizing of Ti6Al4V alloy to improve adhesive bonding for aeronautical applications was investigated. Two electrolytes containing a) hydrogen peroxide (H2O2) and sodium hydroxide (NaOH) and b) chromium trioxide (CrO3) and ammonium bifloride (NH4F2) were used. Anodizing was carried out at 10 V and 303 K for different times. Scanning electron microscopy, confocal microscopy and contact angle measurements with the sessile drop method were used to study morphology, roughness and wettability of the anodic films. The morphology of the anodic layers revealed the presence of randomly distributed pores on the surface whose diameters depend on the anodizing solution, being greater than 150 nm for the basic anodizing solution and less than 100 nm, when the anodizing is carried out in acid anodizing solution. Two key aspects that Ti6Al4V alloy surface must has to favor its adhesive bond to other materials are wettability and roughness. According to the results obtained, the anodic layers formed with acid solution for 30 min have the best wettability conditions and the greater surface roughness, compared with the anodic layers formed by other study conditions. These anodic layers will favor the application of epoxy adhesives normally used for adhesive bonding of Ti6Al4V alloy to polymeric materials.

Study on the effects of nozzle distance to surface roughness of workpiece under minimum quantity lubricant (MQL) milling process

&#x0D; &#x0D; &#x0D; &#x0D; Application of cutting oil during machining process has been the most important contributor for the development of manufacturing sectors. There are many types of machining technologies developed with cutting oil supply system such as minimum quantity lubricant (MQL). With very little supply of lubricant, it can lengthen the cutting tool life and surface roughness of workpiece. Although the low consumption of lubricant is favourable, study on the performance of MQL machining process must be strengthened enough since the high penetration ability of very little amount of lubricant oil is important. Many researches have been carried out since decades ago to study the MQL performance. However, investigation on the effects on nozzle position have not been treated in much detail. Here, this paper is aimed to investigate the effects of nozzle distance to surface roughness of workpiece under MQL milling process. Experimental approach was done mainly under different nozzle distance varied in horizontal direction from the cutting tool. Other than that, the effects of feed rate and spindle speed to the surface roughness were also investigated. As a result, surface roughness increases with increasing feed rate. At lower operation of spindle speed, surface roughness rapidly increases with increasing feed rate compared to higher operated spindle speed. Operation under high feed rate leads to a decreasing surface roughness with increasing spindle speed. Milling under high feed rate for all conditions of nozzle distance can still give a great surface roughness for a workpiece, only if the spindle speed is increased. Surface roughness decreases with increasing distance of nozzle to workpiece in horizontal direction.&#x0D; &#x0D; &#x0D; &#x0D;

Synthesis of Polymeric Matrices for Adsorption and Purification of Endoglucanase

Fil: Boggione, Maria Julia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - Rosario. Instituto de Procesos Biotecnologicos y Quimicos Rosario. Universidad Nacional de Rosario. Facultad de Ciencias Bioquimicas y Farmaceuticas. Instituto de Procesos Biotecnologicos y Quimicos Rosario; Argentina

Determination of Emissivity of Brass Alloy using Infrared Thermographic Technique

Abstract This paper presents the experimental determination of the dependence of emissivity of brass on surface roughness and temperature. The investigation was conducted using the infrared thermographic technique on brass alloy C27200 workpieces with different degrees of surface roughness, during the continuous cooling process. The results obtained showed that the emissivity of the chosen brass alloy increases with greater surface roughness and decreases during the cooling process, its value ranging from 0.07 to 0.19. It was concluded that surface roughness has a greater influence on the increase of the emissivity at higher temperatures, which can be seen in the three-dimensional infrared images. Multiple regression analysis confirmed a strong correlation between the examined parameters and the emissivity, and an original multiple regression model was determined.

ANALYSIS TOOL OVERHANG IN THE MACHINE CNC ET-242 ON SURFACE ROUGHNESS WITH VARIATION OF FEEDING

Lathe is a process to get the shape of the cylindrical workpiece by rotating the workpiece on the spindle and moving the chisel towards the workpiece. To be able to screw the workpiece of the chisel should hang and extend from the turret. The length of the hanging chisel is called the tool overhang (Zelinski, 2005: 1). There is no definite hint of setting the tool overhang and only adjusted between the position of the turret and workpiece. In order to achieve a good surface roughness, usually the overhang tool is arranged to a minimum.In this study the independent variables used are the tool overhang 14 mm, 21 mm, 28 mm, 35mm and feeding 0.15 mm rotation-1, 0.25 mm rotation -1, 0.35 mm. rotation -1. The measured dependent variable is the surface roughness of the workpiece.From the results of testing and data analysis can be concluded that the tool overhang effect on the roughness of the workpiece surface results of the process of lathe in various variations of feeding (feeding). The longer the tool overhang and the greater the feeding motion will result in greater surface roughness. The lowest surface roughness was obtained from a 14 mm long overhang tool and feeding 0.15 mm rotation-1.Keywords : Machine CNC ET-242, Surface Roughness, Feeding Variation.

Physical structure determines compression of membrane biofilms during Gravity Driven Membrane (GDM) ultrafiltration

Increasing transmembrane pressure (TMP) can compress and increase the hydraulic resistance of membrane biofilms. The purpose of the present study is to evaluate how compression of membrane biofilms occurs and how structural rearrangement can affect hydraulic resistance. Biofilms with heterogeneous and homogeneous physical structures were grown in membrane fouling simulators (MFS) in dead-end mode for 20 days with either (i) a nutrient enriched condition with a nutrient ratio of 100:30:10 (C: N: P), (ii) a phosphorus limitation (C: N: P ratio: 100:30:0), or (iii) river water (C: N: P ratio: ca. 100:10:1). The structural and hydraulic response of membrane biofilms to (a) changes in transmembrane pressures (0.06-0.1-0.5-0.1-0.06 bar) and (b) changes in permeate flux (10-15-20-15-10 L/m2/h) were investigated. Optical coherence tomography (OCT) was used to monitor biofilm structural response, and OCT images were processed to quantify changes in the mean biofilm thickness and relative roughness. Nutrient enriched and river water biofilms had heterogeneous physical structures with greater surface roughness (Ra' > 0.2) than homogeneous P limiting biofilms (Ra' < 0.2). Compression of biofilms with rough heterogeneous structures (Ra' > 0.2) was irreversible, indicated by irreversible decrease in surface roughness, partial relaxation in mean biofilm thickness and irreversible increase in hydraulic resistance. Compression of homogeneous biofilm (Ra' < 0.2) was on the other hand reversible, indicated by full relaxation of the biofilms structure and restoration of initial hydraulic resistance. Hydraulic response (i.e., change in the specific biofilm resistance) did not correspond with the change in physical structure of heterogeneous biofilms. The presented study provides a fundamental understanding of how biofilm physical structure can affect the biofilm's response to a change in TMP, with practical relevance for the operation of GDM filtration systems.

Long-term antibacterial and stable chlorhexidine-polydopamine coating on stainless steel 316L

Immobilization of chlorhexidine (CHX) coating on medical devices by utilizing a polydopamine (PDA) film as an intermediate crosslinker, demonstrates a promising value in retarding bacterial growth. However, its long-term antibacterial effect and coating stability are unknown where those features are crucial to sustain long-term application of medical devices. In this study, both properties were evaluated on the CHX-PDA coated SS316L. Greater surface roughness and coating thickness were observed on the SS-PDA-CHX20 compared to the SS-PDA. The CHX adsorption on the PDA film was increased as the CHX concentration increased. The 28 days of ageing process presented gradual coating degradation on the SS-PDA-CHX20 and SS-PDACHX30, releasing the CHX compound. The higher CHX concentration also displayed larger CHX aggregates and higher inhibition zones against E. coli and S. aureus, up to 72 h, indicating the substantivity of antibacterial effect. These properties hold a great potential in preventing bacterial growth on medical devices.

P‐110: Efficient InP‐based Quantum Dot Light Emitting Diodes utilizing a Crosslinkable Hole Transport Layer

We demonstrate efficient InP‐based quantum dot (QD) LEDs utilizing a crosslinkable hole transport layers (HTL). The developed HTL exhibit great solvent resistance and smooth surface roughness. The influence of QD design, HTL structure as well as the corresponding processing of these materials on device performance was investigated.

Optical and Irradiation-Resistant Properties of ITO Films on F46 and PI Substrates

This study investigated indium tin oxide (ITO) films that were deposited on fluororesin-46 (F46) and polyimide (PI) transparent flexible substrates by a DC magnetron sputtering system. The optical properties of ITO films on F46 and PI including transmittance and reflectance in visible, near-infrared, and infrared spectral regions were obtained, and the surface morphology, and optical and electrical properties of ITO/F46 and ITO/PI after vacuum ultraviolet irradiation were investigated. The results showed that the mean transmittances of ITO/F46 and ITO/PI decreased and the sheet resistance increased after the irradiation, and these effects were mainly attributed to the greater surface roughness and crystal defects caused by the irradiation.

Feed substrates influence biofilm formation on reverse osmosis membranes and their cleaning efficiency

The dairy industry is increasingly using reverse osmosis (RO) membranes for concentration of various fluid feed materials such as whey and ultrafiltration (UF) permeate. This study compared the effect of UF permeate and whey on membrane biofilm formation. A Bacillus sp., previously isolated in our laboratory from a cleaning-resistant membrane biofilm, was used to develop 48-h-old static biofilms on RO membrane pieces, using the different feed substrates (UF permeate, whey, and an alternating whey/UF feed). Biofilms were analyzed for viable counts by the swab technique, and we used scanning electron and atomic force microscopy for microstructure imaging. The membrane cleaning process included 6 sequential steps. We observed differences in the resistance pattern of the 3 types of biofilms to the typical cleaning process. The mean pretreatment counts of the 48-h UF permeate biofilms were 5.39 log cfu/cm2, much higher than the whey biofilm counts of 3.44 log, and alternating whey/UF biofilm counts of 4.54 log. After a 6-step cleaning cycle, we found 2.54 log survivors of the Bacillus isolate on UF biofilms, whereas only 1.82 log survivors were found in whey biofilm, and 2.14 log survivors on whey/UF permeate biofilms. In conclusion, the UF permeate biofilms was more resistant to the biofilm cleaning process compared with the whey or whey/UF permeate biofilms. Scanning electron micrographs showed different microstructures of biofilms based on the type of feed. For UF permeate and whey/UF permeate biofilms, bacilli were present in multilayers of cells in aggregates or irregular clusters with foulant layers. In contrast, those in whey biofilms were in monolayers, with a smoother, flatter appearance. Atomic force microscopy analysis indicated that UF permeate biofilms had the greatest surface roughness among the biofilms, reflecting intensified bacterial colonization. The biofilm micro- and nanostructure variations for the 2 feed substrates and their combination may have resulted in differences in their resistance to the cleaning process.