About

Dr. Orlin D. Velev is a S. Frank and Doris Culberson Distinguished Professor in the Department of Chemical & Biomolecular Engineering at North Carolina State University. His research focuses on the development and application of advanced materials and processes in chemical and biomolecular engineering. As a principal investigator, he leads the Velev Research Group, which involves a diverse team of graduate students, postdoctoral fellows, visiting researchers, and undergraduate students. His work encompasses innovative approaches in the field, contributing significantly to the understanding and advancement of materials science and engineering.

Research topics

• Computer Science
• Chemistry
• Organic chemistry
• Engineering
• Materials science
• Environmental science
• Chemical engineering
• Biochemical engineering
• Medicine
• Biology
• Internal medicine
• Biomedical engineering
• Embedded system

Selected publications

• Deposition of hierarchically porous cellulose microfibril films via emulsion templating and drying at ambient temperature

  Utrecht University Repository (Utrecht University) · 2026-03-01

  articleOpen access

  Porous films and coatings based on biocompatible natural renewable materials such as cellulose are of interest to diverse fields such as biomedical devices, insulation, separations, ion exchange, sensing, and packaging. We report the fabrication of hierarchically macro- and nanoporous films of microfibrillated cellulose (MFC) using a novel single-step method based on emulsion templating with recyclable volatile oils. The hierarchical (dual-level) porous cellulosic films are deposited at room temperature by drying of volatile oil-in-water emulsions stabilized by MFC and surfactants. A three-step formation mechanism, based on the evolution of the emulsion droplet size, is proposed. One key factor controlling the resultant structure of the porous films is the vapor pressure difference between the oil and water. Templating with droplets of oil with vapor pressure of the same order as, or lower than, that of water results in formation of macroscopic porous structures. Addition of surfactant can significantly increase the porosity and the thickness of the films by suppressing the coalescence/coarsening of the oil droplets and reducing the flattening effect caused by capillary forces. We demonstrate that these films can be functionalized by silylation to obtain hydrophobic hierarchical dual-level porous films with water contact angles of 70∼116°.

  Publisher

• Unraveling the Antiviral Efficacy of Surfactants: Deactivation of Nonenveloped Viruses through Synergistic Electrostatic Mechanisms

  ACS Nano · 2026-05-02

  articleSenior author

  viral load reduction was achieved using anionic surfactants at pH < 5 or cationic surfactants at pH > 10. Dynamic and electrophoretic light scattering provided data on surfactant-capsid interactions, which we further explored by molecular modeling of the capsid charge distributions across pH ranges using protein sequence data. These results informed a selective-permeation model describing how surfactant efficacy depends on electrostatic interactions─repulsion, attraction, and permeation─with capsid proteins. The model predictions were validated using transmission electron microscopy and were applied to accurately predict the pH inactivation thresholds of ΦX174 phage. The results indicate that both cationic and anionic surfactants could serve as efficient antiviral agents, if the pH of the system favors surfactant penetration through both the inner and outer layers of the capsids. They offer a theoretical framework for the rational design of antiviral formulations for NEVs.

  PublisherDOI

• Filamentous Chitosan Mats by Antisolvent Precipitation in the Regime of Turbulent Liquid Mixing

  Nano Select · 2026-01-01

  articleOpen accessCorresponding

  ABSTRACT An effective method has been developed to produce a new class of filamentous chitosan in the form of a mat of fibers of diameters in the micron‐scale range. It is based on a process of antisolvent precipitation of chitosan from solution under turbulent flow shear generated by a high‐speed colloidal mixer. Chitosan microfibers and microribbons of varying sizes were fabricated by adjusting the mixer's rotational speed. XRD and DTA/DSC/TG analyses revealed that the resulting chitosan fibers possess a partially amorphous microstructure, with the degree of amorphization increasing with the stirring speed. Furthermore, the synthesized chitosan microfibers exhibited the ability to reduce silver ions in daylight, facilitated by their highly accessible, high‐surface‐area amorphous structure, resulting in the deposition of silver nanocrystals smaller than 150 nm on their surfaces. Both the filamentous chitosan mats and their silver‐containing nanocomposites were tested against various bacterial strains, with the nanocomposites exhibiting markedly higher antibacterial activity.

  PublisherOA PDFDOI

• A Contiguous Interlayer/Separator System to Enable Low-Capacity Fade Lithium-Sulfur Batteries

  ECS Meeting Abstracts · 2025-11-24

  article

  The demand for sustainable energy solutions, electric vehicles, and portable electronics is driving the development of high-energy-density, low-cost energy storage technologies. Lithium–sulfur (Li–S) batteries are a promising candidate for next-generation energy storage systems due to their high theoretical energy densities and charge capacities, surpassing conventional lithium-ion (Li-ion) batteries. The transition-metal oxide cathodes used in Li-ion batteries have a capacity limit of about 250 mAh/g, while sulfur boasts a theoretical capacity of around 1672 mAh/g 1 . Additionally, sulfur's natural abundance and lower environmental impact 2 make Li-S batteries a promising alternative. However, their commercialization is hindered by the “polysulfide shuttle effect,” wherein elemental sulfur (S₈) undergoes stepwise electrochemical reduction during discharge to form soluble lithium polysulfides (LiPSs). These intermediates migrate to the lithium anode, resulting in active material loss and severe capacity fading. A promising strategy to mitigate this issue is to incorporate a functional interlayer that acts as a physical and chemical barrier between the cathode and separator, trapping polysulfides and stabilizing redox reactions 3 . In this study, we introduce a multifunctional composite interlayer comprised of poly(vinylidene difluoride)-based soft dendritic colloids (PVDF-SDCs) in combination with carbon nanotubes (CNTs). The PVDF-SDCs were prepared using a turbulent solvent–nonsolvent induced phase-separation method, which yields a highly porous, fibrous morphology with unique adhesive properties. These features enabled the fabrication of two distinct interlayer configurations: a freestanding CNT/PVDF-SDC interlayer (~ 40-μm thick), and a direct-deposited CNT/PVDF-SDC@Celgard interlayer (~ 20-μm thick). Both interlayers were fabricated using shear-driven nanofabrication followed by vacuum-filtration, forming uniform and flexible membranes. The CNT/PVDF-SDC interlayer, with a surface area of 103 m² g⁻¹, exhibits multiscale porosity (ranging from nanometers to microns). These aspects, along with their capacity to provide electronic pathways, promote effective LiPS entrapment, ion/electron transport, and accommodation of volume expansion. Compared to interlayer-free cells, both interlayer designs improved electrochemical performance. The freestanding interlayer achieved an initial capacity of ~1190 mAh g⁻¹ and retained 74% capacity after 400 cycles at 0.2 C. When evaluated at a higher rate of 1 C, the cell maintained ~900 mAh/g with 67% capacity retention over 400 cycles. The CNT/PVDF-SDC@Celgard interlayer demonstrated comparable initial capacity but with greater capacity fade over extended cycling, likely due to its thinner structure and reduced LiPS adsorption capacity. Nonetheless, its integrated design resulted in lower interfacial resistance and improved rate capability due to better physical contact with the separator. Under high-sulfur loading (4 mg cm⁻²) and moderate electrolyte conditions (E/S = 8 μL mg⁻¹), the FS-CNT/PVDF-SDC interlayer delivered an areal capacity of ~ 4.9 mAh cm⁻² and retained 55% after 250 cycles. To validate the robustness of this design, multi-cell tests were conducted under identical conditions ( 4 mg S cm -2 , e/S=8 μL mg⁻¹,0.2C) . The cells displayed overlapping cycling trends and Coulombic efficiencies above 95%, confirming reproducibility and repeatability of the interlayer fabrication process. 1 Manthiram, A.; Fu, Y.; Chung S.-H.; Zu,C.; Su, Y.-S. Rechargeable Lithium-Sulfur Batteries. Chem. Rev. 2014, 114 (23), 11751-11787. https://doi.org/10.1021/cr5000062v. 2 Shen, Z.; Jin, X.; Tian, J.; Li, M.; Yuan, Y.; Zhang, S.; Fang, S.; Fan, X.; Xu, W.; Lu, H.; Lu, J.; and Zhang, H. Cation-Doped ZnS Catalysts for Polysulfide Conversion in Lithium-Sulfur Batteries, Nat. Catal., 2022, 5, 555–563. https://doi.org/10.1038/s41929-022-00804-4 3 Huang, Y.; Lin, L.; Zhang, C.; Liu, L.; Li, Y.; Qiao, Z.; Lin, J.; Wei, Q.; Wang, L.; Xie, Q.; Peng, D.-L. Recent Advances and Strategies toward Polysulfides Shuttle Inhibition for High-Performance Li-S Batteries, Adv. Sci. 2022, 9 (12), 2106004. https://doi.org/10.1002/advs.202106004.

  PublisherDOI

• Design and characterization of a self-powered microneedle microfluidic system for interstitial fluid sampling

  Lab on a Chip · 2025-01-01 · 5 citations

  articleOpen access

  Dermal interstitial fluid (ISF) is a promising source of biomarkers for point-of-care (PoC) diagnostics, yet noninvasive and reliable extraction remains a significant challenge. In this study, we present a fully passive microneedle (MN) platform that integrates hydrogel-forming MNs, a hydrogel-based osmotic pump, and paper microfluidics to enable zero-power ISF extraction and analyte transport from skin models. The system's performance was evaluated using paper microfluidic designs optimized for both bulk fluid uptake and lateral flow-based detection. Osmotic pumping with glycerol and glucose showed comparable extraction efficiencies. Cortisol, a representative stress biomarker, was successfully recovered following 15-minute, 45-minute, and 24-hour sampling durations, demonstrating the platform's suitability for both short-term and extended ISF monitoring. These results highlight the potential of this integrated MN system as a simple, cost-effective, and minimally invasive solution for passive ISF sampling and subsequent biochemical analysis.

  PublisherOA PDFDOI

• Sustainable Biopolymer Colloids: Advances in Morphology for Enhanced Functionalities

  Langmuir · 2025-03-12 · 7 citations

  reviewSenior authorCorresponding

  Biobased polymers such as cellulose, chitin/chitosan, starch, alginate, and lignin are making inroads as sustainable, environmentally safe and biodegradable alternatives to synthetic colloidal materials. This perspective summarizes recent developments in preparation techniques, identifies critical barriers, and proposes future directions for improving the performance and applicability of biopolymer colloidal structures. A major focus is the sustainable colloids morphology as a means of introducing functionality without chemical modification. We discuss the strategies for fabrication of four distinct classes of colloidal morphologies from biobased materials: spherical and nonspherical particles, fibers/fibrils, and films. Their preparation methods can be categorized into physical and chemical approaches. Despite advancements in these methods, challenges persist regarding uniformity, scalability, desired properties, and the need to enhance environmental sustainability. Addressing these challenges is essential for facilitating the transition from synthetic polymers to greener, more sustainable, and microplastic-free colloidal alternatives.

  PublisherDOI

• Mesoscale fractal whey protein particles derived from microscale linear-shaped protein assemblies (Part 1): Manufacturing method and particle characteristics

  Journal of Dairy Science · 2025-12-18

  articleOpen access

  Whey protein isolates (WPI) are widely used in processed foods for their versatile functional properties. Modifying the structural properties of proteins by assembling them into mesoscale or microscale particles may improve their functionality and broaden their applications. This study aims to manufacture and characterize mesoscale whey protein particles (WPP) derived from WPI. Two types of WPP, WPP1 (0.05 mL/min) and WPP2 (0.25 mL/min), were prepared through a multistep approach involving liquid antisolvent (LAS) precipitation, heat treatment, and microfluidization. Liquid antisolvent precipitation was performed by injecting a 20% (wt/vol) WPI dispersion (pH 7) into an ethanol-glycerol mixture (75:25, vol/vol) under laminar flow, followed by heat treatment at 80°C for 20 min as a particle hardening step. This process produced stable fiber- and ribbon-shaped whey protein assemblies (WPA), which served as precursors to WPP. Subsequent microfluidization (150 MPa, 6 passages) reduced the size of WPA, yielding mesoscale WPP with irregular morphologies and a more uniform size distribution, as revealed by microscopy and dynamic light scattering. ζ-Potential and fluorescence labeling indicated higher surface charge and surface hydrophobicity of WPP compared with untreated WPI. The WPP showed internal mass fractal and surface fractal structures at larger length scales, analyzed using small-angle X-ray scattering. Fourier-transform infrared spectroscopy demonstrated an increased fraction of intermolecular β-sheets in WPP, suggesting that hydrogen bonding contributed to their formation. Gel electrophoresis confirmed that disulfide bonds served as the primary cross-links stabilizing the WPP structure. Furthermore, turbidity measurements showed that WPP exhibited superior colloidal phase stability compared with untreated WPI and maintained high colloidal stability under both acidic and neutral pH conditions.

  PublisherDOI

• Technology Roadmap of Micro/Nanorobots

  ACS Nano · 2025-06-27 · 68 citations

  reviewOpen access

  , the field of micro/nanorobots has evolved from science fiction to reality, with significant advancements in biomedical and environmental applications. Despite the rapid progress, the deployment of functional micro/nanorobots remains limited. This review of the technology roadmap identifies key challenges hindering their widespread use, focusing on propulsion mechanisms, fundamental theoretical aspects, collective behavior, material design, and embodied intelligence. We explore the current state of micro/nanorobot technology, with an emphasis on applications in biomedicine, environmental remediation, analytical sensing, and other industrial technological aspects. Additionally, we analyze issues related to scaling up production, commercialization, and regulatory frameworks that are crucial for transitioning from research to practical applications. We also emphasize the need for interdisciplinary collaboration to address both technical and nontechnical challenges, such as sustainability, ethics, and business considerations. Finally, we propose a roadmap for future research to accelerate the development of micro/nanorobots, positioning them as essential tools for addressing grand challenges and enhancing the quality of life.

  PublisherDOI

• Biodegradable Chitosan-Based Stretchable Electronics with Recyclable Silver Nanowires

  ACS Applied Materials & Interfaces · 2025-02-19 · 7 citations

  articleSenior authorCorresponding

  The combination of biodegradability and biocompatibility makes chitosan a principal bioresourced material in biomedical engineering, wearable technology, and medical diagnostics, particularly for integration in human interfaces for soft electronic applications. However, this requires the introduction of soft electronic circuits with the capability of recycling the functional materials, while biodegrading the substrate. This paper presents the development and characterization of biodegradable soft circuits that are constructed using stretchable and flexible substrates from plasticized chitosan and conductive functional wiring from recyclable silver nanowires (AgNWs). The chitosan substrate demonstrates tunable mechanical properties with a maximum stretchability of ∼116%, in addition to desirable characteristics such as transparency, breathability, and controlled degradation. The plasticizing effect of glycerol reduces the rigidity associated with pure chitosan and imparts flexibility and stretchability to the AgNW-chitosan-glycerol (AgNW-Chi-Gly) composite. The AgNWs embedded in the Chi-Gly matrix are highly conductive, and their functionality in soft electronic devices such as strain sensors and electromyography (EMG) sensors is demonstrated. We show that the soft chitosan-based substrates can be subject to biodegradation at the end of their operational lifespan. The AgNWs can be recycled and reused, enhancing the overall sustainability of such soft electronic devices.

  PublisherDOI

• Deposition of hierarchically porous cellulose microfibril films via emulsion templating and drying at ambient temperature

  Food Hydrocolloids · 2025-08-14 · 2 citations

  articleOpen accessSenior authorCorresponding
  PublisherOA PDFDOI

Recent grants

• Manufacturing of Nanofibrillated Soft Dendritic Particles Using Turbulent Liquid Shear

  NSF · $300k · 2018–2023

• NER: Large Scale Synthesis and Assembly of Micro- and Nanoparticles with Dipolar Charge and Anisotropic Shape

  NSF · $114k · 2004–2007

• Establishing the principles and demonstrating the unique properties of novel reconfigurable nano- and microparticle structures bound by liquid bridges

  NSF · $352k · 2016–2021

• CAS: Novel Principles of Fabricating High-Performance Sustainable Packaging Films from Hierarchically Reinforced Biopolymers

  NSF · $374k · 2023–2026

• CAREER: Colloidal Assembly and Transport Using Dielectrophoresis and Novel Media

  NSF · $431k · 2003–2009

Frequent coauthors

• C. Wyatt Shields

  University of Colorado Boulder

  34 shared

• Vesselin N. Paunov

  Nazarbayev University

  33 shared

• Bhuvnesh Bharti

  Louisiana State University

  31 shared

• Eric W. Kaler

  30 shared

• Abraham M. Lenhoff

  University of Delaware

  28 shared

• Krassimir P. Velikov

  University of Amsterdam

  27 shared

• Michael D. Dickey

  North Carolina State University

  25 shared

• Brian G. Prevo

  Cabot (United States)

  23 shared

Education

• Ph.D., Chemical Engineering

  University of California, Berkeley

  1994

• M.S., Chemical Engineering

  University of California, Berkeley

  1991

• B.S., Chemical Engineering

  University of California, Berkeley

  1989

Awards & honors

• Braskem Award for Excellence in Materials Engineering and Sc…
• Langmuir Lecture Award (ACS)
• Rockwell Series Lecturer (Univ. of Houston)
• S. Frank and Doris Culberson Distinguished Professor
• Andreas Acrivos Award for Professional Progress in Chemical…