pH Change in Electroosmotic Flow Hysteresis.

Electroosmotic flow (EOF) or electro-osmosis has been shown to exhibit a hysteresis effect under displacement flow involving two solutions with different concentrations, i.e. the flow velocity for a high-concentration solution displacing a low-concentration solution is faster than the flow velocity in the reverse direction involving the same solution pair. On the basis of our recent numerical analysis, a pH change initiated at the interface between the two solutions has been hypothesized as the cause for the observed anomalies. We report the first experimental evidence of EOF hysteresis induced by a pH change in the bulk solution. pH-sensitive dye was employed to quantify the pH changes in the microchannel during EOF. The electric-field gradient across the boundary of two solutions generates an accumulation or depletion of a minority of pH-governing ions such as hydronium (H3O+) ions, thus inducing pH variations across the microchannel. When a high-concentration solution displaced a lower-concentration solution, a pH increase was observed, while the flow in the reverse direction induced a decrease in pH. This effect causes significant changes to the zeta potential and flow velocity. The experimental results show good quantitative agreement with numerical simulations. This work presents the experimental proof which validates the hypothesis of a pH change during electroomostic flow hysteresis as predicted by numerical analysis. The understanding of pH changes during EOF is crucial for accurate flow manipulation in microfluidic devices and maintenance of constant pH in biological and chemical systems under an electric field.

Effect of nanostructures orientation on electroosmotic flow in a microfluidic channel.

Electroosmotic flow (EOF) is an electric-field-induced fluid flow that has numerous micro-/nanofluidic applications, ranging from pumping to chemical and biomedical analyses. Nanoscale networks/structures are often integrated in microchannels for a broad range of applications, such as electrophoretic separation of biomolecules, high reaction efficiency catalytic microreactors, and enhancement of heat transfer and sensing. Their introduction has been known to reduce EOF. Hitherto, a proper study on the effect of nanostructures orientation on EOF in a microfluidic channel is yet to be carried out. In this investigation, we present a novel fabrication method for nanostructure designs that possess maximum orientation difference, i.e. parallel versus perpendicular indented nanolines, to examine the effect of nanostructures orientation on EOF. It consists of four phases: fabrication of silicon master, creation of mold insert via electroplating, injection molding with cyclic olefin copolymer, and thermal bonding and integration of practical inlet/outlet ports. The effect of nanostructures orientation on EOF was studied experimentally by current monitoring method. The experimental results show that nanolines which are perpendicular to the microchannel reduce the EOF velocity significantly (approximately 20%). This flow velocity reduction is due to the distortion of local electric field by the perpendicular nanolines at the nanostructured surface as demonstrated by finite element simulation. In contrast, nanolines which are parallel to the microchannel have no effect on EOF, as it can be deduced that the parallel nanolines do not distort the local electric field. The outcomes of this investigation contribute to the precise control of EOF in lab-on-chip devices, and fundamental understanding of EOF in devices which utilize nanostructured surfaces for chemical and biological analyses.

Electroosmotic Flow Hysteresis for Dissimilar Anionic Solutions.

Electroosmotic flow (EOF) with two or more fluids is often encountered in various microfluidic applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during displacement flow of solutions with dissimilar anion species. In this investigation, EOF of dissimilar anionic solutions was studied experimentally through the current monitoring method and numerically through finite element simulations. As opposed to other conventional displacement flows, EOF involving dissimilar anionic solutions exhibits counterintuitive behavior, whereby the current-time curve does not reach the steady-state value of the displacing electrolyte. Two distinct mechanics have been identified as the causes for this observation: (a) ion concentration adjustment when the displacing anions migrate upstream against EOF due to competition between the gradients of electromigrative and convective fluxes and (b) ion concentration readjustment induced by the static diffusive interfacial region between the dissimilar fluids which can only be propagated throughout the entire microchannel with the presence of EOF. The resultant ion distributions lead to the flow rate to be directional-dependent, indicating that the flow conditions are asymmetric between these two different flow directions. The outcomes of this investigation contribute to the in-depth understanding of flow behavior in microfluidic systems involving inhomogeneous fluids, particularly dissimilar anionic solutions. The understanding of EOF hysteresis is fundamentally important for the accurate prediction of analytes transport in microfluidic devices under EOF.

Long-term outcomes of mechanochemical ablation using the Clarivein® device for the treatment of great saphenous vein incompetence.

OBJECTIVE: The short-term anatomical success rates of mechanochemical ablation (MOCA) using the Clarivein device (Merit Medical, South Jordan, Utah, United States) in the treatment of great saphenous vein (GSV) incompetence are high. However, the anatomical success rates seem to drop over time. The aim of this study was to determine the long-term outcomes of GSV treatment using the Clarivein and to assess whether specific anatomical features better correlate with clinical or QoL related outcomes. METHODS: This is a single-center, prospective cohort study in follow-up of a multicenter, randomized controlled trial, using Clarivein with liquid polidocanol for the treatment of GSV incompetence. The primary outcome was anatomical success (AS), defined as compete occlusion or a recanalized segment, irrespective of reflux, of <10 cm in length. In addition, reflux-free anatomical success (RF-AS) was determined and defined as a complete occlusion or a recanalized segment with <10 cm of reflux. Clinical success was assessed using the Venous Clinical Severity Score (VCSS) and QoL was assessed using the Dutch version of the Aberdeen Varicose Vein Questionnaire (DAVVQ) and the 36-Item Short Form Health Survey (SF-36). Subgroup analyses were performed based on whether AS or RF-AS was achieved or not. RESULTS: 109 patients (115 limbs) were included. The mean follow-up time was 8.4 ± 0.9 years (range 5.5-10.3 years). AS was seen in 60.5% of limbs and RF-AS was seen in 72.8% of limbs. Compared to baseline, the overall mean VCSS improved from 5.3 ± 2.4 to 4.1 ± 2.4, and the overall median DAVVQ score from 13.1 (7.3-19.4) to 10.5 (4.8-15.8) (p<0.001). Improvement in VCSS was only significant in patients with successful treatment: 5.5 ± 2.4 to 3.7 ± 2.5 (p<.001) if AS was achieved and 5.0 ± 1.7 to 4.5 ± 1.9 (p=.20) if AS was not achieved. The same results were found for DAVVQ scores: 13.5 (8.7-20.6) to 10.3 (3.0-14.5) (p<001) if AS was achieved and 12.9 (8.3-19.3) to 10.8 (6.7-18.2) (p=.35) if AS was not achieved. Regarding the overall SF-36 scores, the domains vitality, mental health and general health worsened significantly. CONCLUSION: In over eight-years of follow-up, anatomical success after the treatment of GSV incompetence using the Clarivein device decreased to 60.5%. However, clinical scores and disease-specific QoL still improved significantly compared to baseline. We found no convincing evidence that the absence of reflux correlates better with clinical and quality of life related outcomes compared to recanalization irrespective of reflux.

Academic performance of students in an accelerated medical pathway.

Accelerated medical school curricula, such as three-year programs, have gained attention in recent years but studies evaluating their impact are still scarce. This study examines the Fully Integrated Readiness for Service Training (FIRST) program, a three-year accelerated pathway, to assess its impact on students' academic performance preparedness for residency. In this observational study, we compared the academic outcomes of FIRST program students to traditional four-year curriculum students from 2018 to 2023. We analyzed multiple metrics, including exam performance (United States Medical Licensing Examination Step scores, shelf exam scores, and pre-clinical course scores) and clinical performance scores during the application and individualization phases. Analysis of Variance was used to examine the effect of accelerated pathway program experience relative to traditional 4-year medical school curriculum on the learning outcomes. FIRST program students were on average 1.5 years younger upon graduation than their traditional peers. While FIRST program students scored slightly lower on Step 2 Clinical Knowledge (CK), they exhibited no significant differences in other exam scores or clinical performance relative to the traditional students. Notably, FIRST students achieved equivalent clinical performance ratings during critical clerkships and rotations. Our findings suggest that a three-year medical school curriculum can effectively prepare students for residency and produce graduates with comparable medical knowledge and clinical skills, offering potential benefits in terms of financial relief and personal well-being for medical students.

Teaching social determinants through geographic information system mapping.

BACKGROUND: Many institutions in undergraduate medical education have developed unique curricula to teach social determinants of health (SDOH). Geographic information system (GIS) mapping is one tool that learners could use to understand our built environment and its correlation with health outcomes through data analysis, visualization and active learning. APPROACH: At the University of North Carolina School of Medicine, medical students participate in a 4-year longitudinal curriculum on social and health systems science with the final year dedicated to self-directed learning. This final year course incorporates a GIS-based online module to help students apply their understanding of the health impacts of SDOH. Students create online maps with simulated patient data and identify 'hotspots' with map overlays using ArcGIS software. Students write reflections on their maps based on the implications of SDOH. Thematic analysis of these reflections identified patterns within the narrative data. EVALUATION: From March 2020 to February 2021, 148 fourth-year medical students participated in the GIS learning module. Five major themes were identified: Explored Social Determinant Topics, Inclusion of Geo-mapping in Curriculum, Utility of Geo-mapping in Healthcare, Future Application of ArcGIS for Personal Use, Impressions of ArcGIS Software. Students showed engagement and interest in the exercise, and responses were overall positive. Responses showed understanding of the application of ArcGIS and demonstrated knowledge of social determinants of health. IMPLICATIONS: A self-directed, active learning online module using GIS mapping offers a generally popular, eye-opening and unique method for teaching SDOH in undergraduate medical education.

A comparison of patient-reported outcome measures following technical success and technical failure in the treatment of great saphenous vein incompetence using ClariVein: A subanalysis of a multicenter randomized controlled trial comparing 2% and 3% polidocanol.

OBJECTIVE: This study aimed to compare patient-reported outcomes after technical success (TS) and technical failure (TF) in treating great saphenous vein incompetence (GSV) with ClariVein. METHODS: A subanalysis of a previous trial was conducted on symptomatic GSV incompetence patients who received ClariVein treatment with 2% or 3% polidocanol (POL) and were followed for 6 months. Blinding was implemented for observers and patients, and data from both POL groups were combined. TS was defined as at least 85% occlusion of the treated vein, while TF indicated failure to meet TS criteria. Secondary outcomes included Venous Clinical Severity Score (VCSS), Aberdeen Varicose Vein Questionnaire (AVVQ), and Short-Form 36 Health Survey Questionnaire (SF-36). RESULTS: Among the 364 patients included, the TS rate was 64.5%. Comparison of VCSS, AVVQ, and SF-36 scores between TS and TF groups did not yield significant differences. CONCLUSION: This study indicates no significant variation in VCSS, AVVQ, and SF-36 scores between patients experiencing TS and TF following ClariVein treatment for GSV insufficiency.

Continuous cell separation using dielectrophoresis through asymmetric and periodic microelectrode array.

The study presents a dielectrophoretic cell separation method via three-dimensional (3D) nonuniform electric fields generated by employing a periodic array of discrete but locally asymmetric triangular bottom microelectrodes and a continuous top electrode. Traversing through the microelectrodes, heterogeneous cells are electrically polarized to experience different strengths of positive dielectrophoretic forces, in response to the 3D nonuniform electric fields. The cells that experience stronger positive dielectrophoresis are streamed further in the perpendicular direction to the fluid flow, leaving the cells that experience weak positive dielectrophoresis, which continue to traverse the microelectrode array essentially along the laminar flow streamlines. The proposed method has achieved 87.3% pure live cells harvesting efficiency from a live/dead NIH-3T3 cells mixture, and separation of MG-63 cells from erythrocytes with a separation efficiency of 82.8%. The demonstrated cell separation shows promising applications of the DEP separator for cell separation in a continuous mode.

Parental Depression and Leisure Activity Engagement on Children's Gaming Disorder: A Dyadic Study.

Nowadays, playing both online and offline video games is a popular leisure activity among youngsters, but excessive gaming activity engagement may lead to gaming disorder that disrupts daily functioning. Identifying risk and protective factors of this emerging problem is thus essential for devising prevention and intervention strategies. This mixed-method, cross-sectional study aimed to examine the roles of parental depressive symptoms and children's leisure activity engagement on children's gaming disorder symptoms. Furthermore, the moderating roles of risky and protective leisure activity engagement were investigated. The sample comprised 104 parent-child dyads recruited from a population-based survey (parents: Mage = 45.59 years, SD = 6.70; children: Mage = 11.26 years; SD = 4.12). As predicted, parental depressive symptoms and children's gaming activity engagement were positively associated with children's gaming disorder symptoms, whereas children's literacy activity engagement was negatively associated with these symptoms. Moreover, engagement in these two types of leisure activity moderated the association between parental depressive symptoms and children's gaming disorder symptoms in distinct manners, further indicating literacy activities as beneficial and gaming activities as risk-enhancing. These new findings imply that parental depressive symptoms and children's leisure activity engagement should be considered when designing parent-based programs for gaming disorder prevention and intervention.

The Predictive Effects of Family and Individual Wellbeing on University Students' Online Learning During the COVID-19 Pandemic.

The COVID-19 pandemic has significantly changed university students' life routines, such as prolonged stay at home and learning online without prior preparation. Identifying factors influencing student online learning has become a great concern of educators and researchers. The present study aimed to investigate whether family wellbeing (i.e., family support and conflict) would significantly predict university students' online learning effectiveness indicated by engagement and gains. The mediational role of individual wellbeing such as life satisfaction and sleep difficulties was also tested. This study collected data from 511 undergraduate students (Mean age = 20.04 ± 1.79 years, 64.8% female students) via an online survey. Structural equation modeling analysis revealed positive effects of family support on students' learning engagement and gains through the mediational effects of life satisfaction and sleep difficulties. In contrast to our expectation, family conflict during the pandemic also positively predicted students' learning gains, which, however, was not mediated by individual wellbeing. The findings add value to the existing literature by delineating the inter-relationships between family wellbeing, individual wellbeing, and online learning effectiveness. The study also sheds light on the unique meaning of family conflict, which needs further clarification in future studies.

Multi-Foci Laser Separation of Sapphire Wafers with Partial Thickness Scanning.

With multi-foci laser cutting technology for sapphire wafer separation, the entire cross-section is generally scanned with single or multiple passes. This investigation proposes a new separation technique through partial thickness scanning. The energy effectivity and efficiency of the picosecond laser were enhanced through a two-zone partial thickness scanning by exploiting the internal reflection at the rough exit surface. Each zone spanned only one-third thickness of the cross-section, and only two out of three zones were scanned consecutively. A laser beam of 0.57 W and 50 kHz pulse repetition rate was split into 9 foci, each with a 2.20 µm calculated focused spot diameter. By only scanning the top two-thirds sample thickness, first its middle section then upper section, a cleavable sample could result. This was achieved with the lowest energy deposition at the fastest scanning speed of 10 mm/s investigated. Although with partial thickness scanning only, counter intuitively, the cleaved sample had a previously unattained uniform roughened sidewall profile over the entire thickness. This is a desirable outcome in LED manufacturing. As such, this proposed scheme could attain a cleavable sample with the desired uniformly roughened sidewall profile with less energy usage and faster scanning speed.

A multicenter, randomized, dose-finding study of mechanochemical ablation using ClariVein and liquid polidocanol for great saphenous vein incompetence.

BACKGROUND: The purpose of the present study was to identify the ideal polidocanol (POL) concentration for mechanochemical ablation (MOCA) of the great saphenous vein (GSV) using the ClariVein system (Merit Medical, South Jordan, Utah). METHODS: We performed a multicenter, randomized, controlled, single-blind trial with a follow-up period of 6 months. Patients with symptomatic primary truncal GSV incompetence were randomized to MOCA + 2% POL liquid (2% group) or MOCA + 3% POL liquid (3% group). The primary outcome was technical success (TS), defined as an open part of the treated vein segment of ≤10 cm in length. The secondary outcomes were alternative TS, defined as ≥85% occlusion of the treated vein segment, postoperative pain, venous clinical severity scores, Aberdeen varicose vein questionnaire scores, and short-form 36-item health survey questionnaire scores, and complications. RESULTS: From 2012 to 2018, 364 patients (375 limbs) were included, of which, 189 limbs were randomly allocated to the 2% group and 186 to the 3% group. The TS rate at 6 months was 69.8% in the 2% group vs 78.0% in the 3% group (P = .027). A higher overall TS rate was seen in GSVs of ≤5.9 mm compared with GSVs >5.9 mm (84.3% vs 59.5%, respectively; P < .001). The alternative TS rate at 6 months was 61.4% in the 2% group and 67.7% in the 3% group (P = .028). The venous clinical severity scores, Aberdeen varicose vein questionnaire scores, and most short-form 36-item health survey questionnaire domains had improved in both groups (P < .002). Postprocedural pain was low. Two pulmonary embolisms and two deep vein thromboses were seen. Superficial venous thrombosis had occurred more often in the 3% group (18 vs 8 in the 2% group; P = .033). CONCLUSIONS: The results from the present study showed a higher success rate for MOCA with 3% POL liquid than for MOCA with 2% POL liquid at 6 months of follow-up. However, the difference in quality of life was not significant. Long-term follow-up studies are required to investigate whether these results will be sustained in the future.

Tips and tools to help refine your approach to chest pain.

Which history and exam findings have high predictive value for different causes of chest pain? Which decision tool can best assess for CAD in your practice setting?

Electroosmotic Flow Hysteresis for Fluids with Dissimilar pH and Ionic Species.

Electroosmotic flow (EOF) involving displacement of multiple fluids is employed in micro-/nanofluidic applications. There are existing investigations on EOF hysteresis, i.e., flow direction-dependent behavior. However, none so far have studied the solution pair system of dissimilar ionic species with substantial pH difference. They exhibit complicated hysteretic phenomena. In this study, we investigate the EOF of sodium bicarbonate (NaHCO3, alkaline) and sodium chloride (NaCl, slightly acidic) solution pair via current monitoring technique. A developed slip velocity model with a modified wall condition is implemented with finite element simulations. Quantitative agreements between experimental and simulation results are obtained. Concentration evolutions of NaHCO3-NaCl follow the dissimilar anion species system. When NaCl displaces NaHCO3, EOF reduces due to the displacement of NaHCO3 with high pH (high absolute zeta potential). Consequently, NaCl is not fully displaced into the microchannel. When NaHCO3 displaces NaCl, NaHCO3 cannot displace into the microchannel as NaCl with low pH (low absolute zeta potential) produces slow EOF. These behaviors are independent of the applied electric field. However, complete displacement tends to be achieved by lowering the NaCl concentration, i.e., increasing its zeta potential. In contrast, the NaHCO3 concentration has little impact on the displacement process. These findings enhance the understanding of EOF involving solutions with dissimilar pH and ion species.

Electrical Resistance Reduction Induced with CO2 Laser Single Line Scan of Polyimide.

We conducted a laser parameter study on CO2 laser induced electrical conductivity on a polyimide film. The induced electrical conductivity was found to occur dominantly at the center of the scanning line instead of uniformly across the whole line width. MicroRaman examination revealed that the conductivity was mainly a result of the multi-layers (4-5) of graphene structure induced at the laser irradiation line center. The graphene morphology at the line center appeared as thin wall porous structures together with nano level fiber structures. With sufficient energy dose per unit length and laser power, this surface modification for electrical conductivity was independent of laser pulse frequency but was instead determined by the average laser power. High electrical conductivity could be achieved by a single scan of laser beam at a sufficiently high-power level. To achieve high conductivity, it was not efficient nor effective to utilize a laser at low power but compensating it with a slower scanning speed or having multiple scans. The electrical resistance over a 10 mm scanned length decreased significantly from a few hundred Ohms to 30 Ohms when energy dose per unit length increased from 0.16 J/mm to 1.0 J/mm, i.e., the laser power increased from 5.0 W to 24 W with corresponding power density of 3.44 × 10 W/cm2 to 16.54 W/cm2 respectively at a speed of 12.5 mm/s for a single pass scan. In contrast, power below 5 W at speeds exceeding 22.5 mm/s resulted in a non-conductive open loop.

Multi-Foci Division of Nonlinear Energy Absorption on Ultrashort Pulse Laser Singulation of Sapphire Wafers.

The multi-foci division of through thickness nonlinear pulse energy absorption on ultrashort pulse laser singulation of single side polished sapphire wafers has been investigated. Firstly, it disclosed the enhancement of energy absorption by the total internal reflection of the laser beam exiting from an unpolished rough surface. Secondly, by optimizing energy distribution between foci and their proximity, favorable multi-foci energy absorption was induced. Lastly, for effective nonlinear energy absorption for wafer separation, it highlighted the importance of high laser pulse energy fluence at low pulse repetition rates with optimized energy distribution, and the inadequacy of increasing energy deposition through reducing scanning speed alone. This study concluded that for effective wafer separation, despite the lower pulse energy per focus, energy should be divided over more foci with closer spatial proximity. Once the power density per pulse per focus reached a threshold in the order of 1012 W/cm2, with approximately 15 µm between two adjacent foci, wafer could be separated with foci evenly distributed over the entire wafer thickness. When the foci spacing reduced to 5 µm, wafer separation could be achieved with pulse energy concentrated only at foci distributed over only the upper or middle one-third wafer thickness.

Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting.

Despite its advantages of scalable process and cost-effectiveness, nanoimprinting faces challenges with imprinting hard materials (e.g., crystalline metals) at low/room temperatures, and with fabricating complex nanostructures rapidly (e.g., heterojunctions of metal and oxide). Herein, we report a room temperature ultrasonic nanoimprinting technique (named nanojackhammer) to address these challenges. Nanojackhammer capitalizes on the concentration of ultrasonic energy flow at nanoscale to shape bulk materials into nanostructures. Working at room temperature, nanojackhammer allows rapid fabrication of complex multi-compositional nanostructures made of virtually all solid materials regardless of their ductility, hardness, reactivity and melting points. Atomistic simulations reveal a unique alternating dislocation generation and recovery mechanism that significantly reduces the imprinting force under ultrasonic cyclic loading. As a proof-of-concept, a metal-oxide-metal plasmonic nanostructure with built-in nanogap is rapidly fabricated and employed for biosensing. As a fast, scalable, and cost-effective nanotechnology, nanojackhammer will enable various unique applications of complex nanostructures in optoelectronics, biosensing, catalysis and beyond.

Continuous sorting and separation of microparticles by size using AC dielectrophoresis in a PDMS microfluidic device with 3-D conducting PDMS composite electrodes.

Soft lithography technology allows for the development of numerous PDMS-based microfluidic devices for manipulation of particles and cells. However, integrating metallic electrodes with PDMS-based channel structures is challenging due to weak adhesion between metal and PDMS. To overcome this issue, we develop a new PDMS-based microfluidic device for continuous sorting and separation of microparticles by size using AC dielectrophoresis (DEP) with 3-D conducting PDMS composites as sidewall electrodes. The composites are synthesized by mixing silver powders with PDMS gel and such composite electrodes can easily be integrated with the PDMS microchannels. Furthermore, the sidewall electrodes also allow DEP forces to distribute three dimensionally, thus enhancing DEP effects in the entire region of channels. The capability of such PDMS-based microfluidic device is demonstrated for continuously sorting and separating 10 and 15 mum particles, and also for separating 5 from 10 mum particles. Together with experimental results, analysis of particle's trajectory based on Lagrangian approach provides insights into how microparticles transport under the effects of hydrodynamic and DEP forces in the present PDMS-based microfluidic device.

Bone Tumors: Benign Bone Tumors.

Primary benign bone tumors are uncommon and most often affect children and young adults. They typically are detected incidentally on imaging, though some patients present with pain, swelling, or other symptoms. The four main categories of benign bone tumor are: bone-forming (eg, osteoid osteoma, osteoblastoma, fibrous dysplasia, enostosis), cartilage-forming (eg, osteochondroma, enchondroma), connective tissue, and vascular; the latter two are rare. A fifth category is idiopathic (eg, giant cell tumor, aneurysmal bone cyst, simple bone cyst). Osteochondromas are the most common, accounting for 30% to 35% of benign bone tumors. Giant cell tumors account for 20%, osteoblastomas for 14%, and osteoid osteomas for 12%. All others are less common. Diagnosis mainly is via imaging; biopsy rarely is required. Management varies with tumor type, location, symptoms, and risk of recurrence. Some (eg, enchondroma, osteochondroma, fibrous dysplasia, enostosis) typically are asymptomatic, and generally require no intervention. Others (eg, osteoid osteoma, aneurysmal bone cyst, simple bone cyst) can cause symptoms and require percutaneous ablation or surgery. Still others (eg, giant cell tumor, osteoblastoma) can be aggressive and require surgery and other therapies. Malignant transformation is rare for all benign bone tumors, but patients with these tumors should be monitored with serial imaging.

Numerical Investigation of Nanostructure Orientation on Electroosmotic Flow.

Electroosmotic flow (EOF) is fluid flow induced by an applied electric field, which has been widely employed in various micro-/nanofluidic applications. Past investigations have revealed that the presence of nanostructures in microchannel reduces EOF. Hitherto, the angle-dependent behavior of nanoline structures on EOF has not yet been studied in detail and its understanding is lacking. Numerical analyses of the effect of nanoline orientation angle θ on EOF to reveal the associated mechanisms were conducted in this investigation. When θ increases from 5° to 90° (from parallel to perpendicular to the flow direction), the average EOF velocity decreases exponentially due to the increase in distortion of the applied electric field distribution at the structured surface, as a result of the increased apparent nanolines per unit microchannel length. With increasing nanoline width W, the decrease of average EOF velocity is fairly linear, attributed to the simultaneous narrowing of nanoline ridge (high local fluid velocity region). While increasing nanoline depth D results in a monotonic decrease of the average EOF velocity. This reduction stabilizes for aspect ratio D/W > 0.5 as the electric field distribution distortion within the nanoline trench remains nearly constant. This investigation reveals that the effects on EOF of nanolines, and by extrapolation for any nanostructures, may be directly attributed to their effects on the distortion of the applied electric field distribution within a microchannel.