Nenad Miljkovic

• PhD
• Professor (Associate) at University of Illinois Urbana-Champaign

Infrared thermography is a powerful tool for studying liquid-to-vapor phase change processes. However, its application has been limited in the study of vapor-to-liquid phase transitions due to the presence of complex liquid dynamics, multiple phases within the same field of view, and experimental difficulty. Here, we develop a calibration framework...

To address growing water scarcity, we must improve the energy efficiency of thermal desalination technologies such as air gap membrane distillation. However, promising functional materials such as slippery liquid infused porous surfaces have not yet implemented for any desalination technology. Here, we fabricate and test slippery liquid infused por...

Droplets are prone to adhere or “pin” on solid surfaces which contain unavoidable micro- and nanoscale surface defects formed through chemical and topographical heterogeneity. To initiate droplet motion, potential energy gradients, surface energy gradients, or external energy input are needed. Here, in contrast to established wisdom, we show that p...

Liquid–vapor phase-change heat transfer plays an important role in many industrial systems, ranging from power generation and air conditioning to water desalination, food processing, and thermal management of electronics and data centers. Recent advances in micro/nanofabrication have enabled desirable manipulation of multiscale dynamics governing d...

Thermal runaway (TR) modeling is one of the primary tools that can be used to overcome challenges associated with lithium-ion battery (LIB) safety. Among all LIB accidents that have occurred over the past decade, Internal Short Circuit (ISC) remains the most common trigger mechanism. Many available models in the literature either use a simplified a...

Condensation is a vital process integral to numerous industrial applications. Enhancing condensation efficiency through dropwise condensation on hydrophobic surfaces is well-documented. However, no surfaces have been able to repel liquids with extremely low surface tension, such as fluorinated solvents, during condensation, as they nucleate and com...

Power densification is making thermal design a key step in the development of future electrical devices. Systems such as data centers and electric vehicles are generating more heat, which requires efficient cooling to maintain the electronics at temperatures below their limits and to ensure reliability. Immersion cooling has emerged as a promising...

To tackle the formidable challenges posed by extreme cold weather events, significant advancements have been made in developing functional surfaces capable of efficiently removing accreted ice. Nevertheless, many of these surfaces still require external energy input, such as electrical power, which raises concerns regarding their alignment with glo...

The global lithium-ion battery recycling capacity needs to increase by a factor of 50 in the next decade to meet the projected adoption of electric vehicles. During this expansion of recycling capacity, it is unclear which technologies are most appropriate to reduce costs and environmental impacts. Here, we describe the current and future recycling...

The layout of battery cells in liquid-based battery thermal management systems determines the temperature distribution within a battery pack, which, in turn, affects the safety, reliability, and efficiency of the battery system. Therefore, real-time heat map prediction is of great importance for battery design optimization and control strategy refi...

We report the observation of two identical Leidenfrost droplets rebounding from each other after a head-on collision on a hot surface, resembling billiard ball collision. The observed phenomenon contradicts the established understanding that predicts the coalescence of two colliding Leidenfrost droplets. The collision dynamics of the Leidenfrost dr...

Micro- and nanostructured surfaces offer the potential to enhance two-phase heat transfer. However, the mechanisms behind these enhancements are not well-understood due to insufficient diagnostic methods, leading to reliance on trial-and-error surface development. We introduce in situ boroscopy to investigate microscale bubble dynamics during flow...

Ice formation and accumulation on aircraft is a major problem in aviation. Icing is directly responsible for aircraft incidents, limiting the safety of air travel and requiring expensive, and sometimes ineffective deicing strategies. Furthermore, electrification of aircraft platforms leads to difficulties with integration of legacy deicing methods...

We report here multiphase direct numerical simulations of a recently discovered passive mechanism of self-cleaning on superhydrophobic surfaces. The removal of contaminants is governed by coalescence of a single droplet with a particle of micrometer size, where the droplet initiates spontaneous spreading on the particle and drives particle–droplet...

Passive battery thermal management systems (BTMSs) are critical for mitigation of battery thermal runaway (TR). Phase change materials (PCMs) have shown promise for mitigating transient thermal challenges. Fluid leakage and low effective thermal conductivity limit PCM adoption. Furthermore, the thermal capacitance of PCMs diminishes as their latent...

Phase change materials (PCMs) present opportunities for efficient thermal management due to their high latent heat of melting. However, a fundamental challenge for PCM cooling is the presence of a growing liquid layer of relatively low thermal conductivity melted PCM that limits heat transfer. Dynamic phase change material (dynPCM) uses an applied...

Agrivoltaics (AV), the integration of agriculture and photovoltaic (PV) technology, can provide solutions to address land use conflicts associated with growing demands for food, energy, and water resources. Currently, there is no method to address the site-specific characteristics of AV (altered microclimate, crop yield, PV and crop design) in a pl...

A virtual testbed simulation framework is created for the economic, reliability, and lifetime analysis of battery thermal management control strategies in electric vehicles. The system-level model is created in the MATLAB environment using the Simscape library and custom components are developed as required. A lumped parameter coupled electro-therm...

One of the primary concerns during the heating operation of air source heat pumps is the frosting phenomena on the evaporator's surface, which serves as the outdoor heat exchanger. In outdoor conditions characterized by low temperatures and high humidity, the water vapor in the air condenses and freezes on the external surface of the evaporator. Va...

The oil circulation ratio (OCR) significantly impacts automotive air conditioning system performance, both at system and component levels. It represents the mass percentage of oil in a representative oil-refrigerant mixture sample drawn from the system at steady state. With industries increasingly favoring low-OCR compressors, accurate and repeatab...

For vapor compression systems, the standard method for measuring the oil circulation ratio (OCR) is via sampling, as described in the ASHRAE standard 41.4. Sampling is tedious, alters the steady state of the system and can depend on several factors such as refrigerant-oil miscibility and sampling cylinder orientation. Many compressor manufacturers...

The development of lithium-ion battery technology has ensured that battery thermal management systems are an essential component of the battery pack for next-generation energy storage systems. Using dielectric immersion cooling, researchers have demonstrated the ability to attain high heat transfer rates due to the direct contact between cells and...

The greater geometrical design freedom offered by additive manufacturing (AM) as compared to the conventional manufacturing method has attracted increasing interest in AM to develop innovative and complex designs for enhanced performance. However, the difference in material composition and surface properties from conventional alloys has made surfac...

Knowledge of condensate shedding droplet dynamics provides important information for the characterization of two-phase heat and mass transfer phenomena. Detecting and segmenting the droplets during shedding requires considerable time and effort if performed manually. Here, we developed a self-supervised deep learning model for segmenting shedding d...

This article demonstrates the use of topology optimization (TO) to generate optimal fin designs capable of high heat flux removal without increasing the pumping power. We use pseudo-3D modeling validated against 3D simulations for thermal-hydraulic performance, which reduces the computational intensity and allows for a wider range of designs to be...

Thin films of amorphous silicon (a-Si) coated on metals such as nickel (Ni) are one of the most promising anode architectures for high-energy-density lithium-ion (Li-ion) batteries. The performance and longevity of batteries with this type of electrode depend on the integrity of the Ni/a–Si interface. The integrity of the a-Si /Ni bonded interface...

A nanostructured copper oxide (nCO) coating which can be electrochemically reduced to copper metal is demonstrated as an anti‐reflection coating, enabling interference lithography of three‐dimensionally structured templates on a surface compatible with subsequent electrodeposition steps. The nCO presents a black needle‐like structure which effectiv...

Icing of seawater droplets is capable of causing catastrophic damage to vessels, buildings, and human life, yet it also holds great potential for enhancing applications such as droplet-based freeze desalination and anti-icing of sea sprays. While large-scale sea ice growth has been investigated for decades, the icing features of small salty droplet...

To efficiently increase the energy density of the battery pack, cell-to-pack has become a widely used packing technology for electric vehicles. Among different cooling methods, immersion cooling with feedback control can provide robust thermal management to keep the temperature of all battery cells within a desirable range, therefore, ensuring a go...

A consensus was built in the first half of the 20th century, which was further debated more than 3 decades ago, that the wettability and condensation mechanisms on smooth solid surfaces are modified by the adsorption of organic contaminants present in the environment. Recently, disagreement has formed about this topic once again, as many researcher...

Thin (∼ 100 nm thick) hydrophobic polymer films are used in a plethora of applications where water repellency is required. However, hydrophobic film implementation in industry is limited due to poor durability. Thin hydrophobic film blistering during condensation has been identified as one of the main mechanisms associated with failure. Yet, disagr...

A virtual testbed simulation framework is created for the economical and reliability analysis of battery thermal management control strategies in electric vehicles (EVs). The economic benefit of extending battery lifetime by optimal thermal conditioning is weighed against the corresponding energy cost of the operation, allowing for the adoption of...

As battery usage keeps growing due to a boom in the electric vehicles market, battery recycling has become a crucial issue. Cathode active material is the most valuable component of the battery and attracts researchers’ attention. Much research has been focused on finding the optimal condition of a certain hydrometallurgical recycling process for c...

Quantifying the nucleation processes involved in liquid-vapor phase-change phenomena, while dauntingly challenging, is central in designing energy conversion and thermal management systems. Recent technological advances in the deep learning and computer vision field offer the potential for quantifying such complex two-phase nucleation processes at...

Superhydrophobicity is a remarkable adaptation observed in various natural surfaces, which can potentially play a crucial role in the efficient functioning of numerous applications. The attainment of long-lasting or “durable” superhydrophobicity has significant implications for global energy production, water conservation, and the overall carbon fo...

Seventy percent of global electricity is generated by steam-cycle power plants. A hydrophobic condenser surface within these plants could boost overall cycle efficiency by 2%. In 2022, this enhancement equates to an additional electrical power generation of 1000 TWh annually, or 83% of the global solar electricity production. Furthermore, this effi...

Micro and nanostructures can delay frost and ice buildup, improve defrosting efficiency, and reduce water retention. Here, we examine the impact of nanostructures on aluminum evaporators during frosting and defrosting inside of a 20.5 ft3 commercial food refrigerator. We use scalable manufacturing methods to generate structures on the external surf...

Among different battery packaging technologies, cell-to-pack is a widely used method to reduce the cost and increase the volumetric density of battery packs. Unlike the traditional cell-to-module technology, it requires more robust management to keep the temperature uniformity of all cells within a desirable range to ensure good pack performances....

With the increasing demand for electric vehicles, battery recycling is becoming a critical topic for lowering the environmental impact of wasted batteries. Hydrometallurgical recycling is a widely used method, and the cathode leaching process is essential for hydro metallurgical recycling. This work comprehensively compares leaching processes for L...

Passive daytime radiative cooling (PDRC) has the potential to reduce energy demand and mitigate global warming. However, surface contamination from dust and bacterial buildup limits practical PDRC applications. Here, we develop a hierarchically patterned nanoporous composite (HPNC) using a facile template-molding fabrication method to integrate PDR...

Juxtaposing hydrophilicity and hydrophobicity on the same surface, known as hybrid surface engineering, can enhance phase-change heat transfer. However, controlling hydrophilicity on hybrid surfaces in a scalable fashion is a challenge, limiting their application. Here, using widely available metal meshes with variable dimensions and by controlling...

In-tube condensation of refrigerants is an important process which affects thermal efficiency in many applications, ranging from refrigeration and air conditioning to electronics thermal management. In-tube heat transfer and pressure drop are important to heat exchanger sizing and design. In this work, micro-and nanostructured surfaces are applied...

Flow boiling is used in air-conditioning and refrigeration, thermal management of electronics, distillation , chemical synthesis, desalination, power generation, and cryogenics. To enhance the flow boiling heat transfer, internally finned tubing has been widely used. In this work, we demonstrate a fabrication method to generate internal microstruct...

Rapid implementation of renewable energy technologies has exacerbated the potential for economic loss and safety concerns caused by ice and frost accretion, which occurs on the surfaces of wind turbine blades, photovoltaic panels, and residential and electric vehicle air-source heat pumps. The past decade has seen advances in surface chemistry and...

Soft, wireless physiological sensors that gently adhere to the skin are capable of continuous clinical-grade health monitoring in hospital and/or home settings, of particular value to critically ill infants and other vulnerable patients, but they present risks for injury upon thermal failure. This paper introduces an active materials approach that...

Liquid–vapor phase change phenomena such as boiling and condensation are processes widely implemented in industrial systems such as power plants, refrigeration and air conditioning systems, desalination plants, water processing installations and thermal management devices due to their enhanced heat transfer capability when compared to single-phase...

Single-phase liquid-cooled heat sinks are a preferred mode of thermal management for many power dense electronic applications. This paper studies the design, optimization, and thermal-hydraulic performance of polymer manifolds directing coolant to the base plate of multi-chip power modules. Direct cooling eliminates the need for thermal interface m...

Incorporation of micro- and nanostructures on metals can improve thermal performance in a variety of applications. In this work, we demonstrate two independent highly scalable and cost-effective methods to generate micro- and nanostructures on copper and stainless steel, two widely used metals in energy and thermal applications. The performance of...

The surface energy of graphene and its chemical derivatives governs fundamental interfacial interactions like molecular assembly, wetting, and doping. However, quantifying the surface energy of supported two-dimensional (2D) materials, such as graphene, is difficult because (1) they are so thin that electrostatic interactions emanating from the und...

Vapor condensation is widely used in industrial systems due to its effective heat and mass transfer when compared to single-phase thermal transport. In particular, dropwise condensation can significantly enhance heat transfer performance due to rapid droplet shedding and promotion of additional nucleation sites for vapor condensation. Recently, lub...

Solid-liquid interactions are central to diverse processes. The interaction strength can be described by the solid-liquid interfacial free energy (γSL), a quantity that is difficult to measure. Here, we present the direct experimental measurement of γSL for a variety of solid materials, from nonpolar polymers to highly wetting metals. By attaching...

The voltage shielding capacity of a hydrofluoroether type fluid, specifically HFE7500 along with that of Parylene C based conformal surface coatings are explored. Both voltage blocking technologies demonstrated an ability to maintain good voltage blocking capacity even when exposed to field strengths as high as 16.8kV/mm in the case of the dielectr...

Hypothesis: Droplet spreading governs various daily phenomena and industrial processes. Insights about microdroplet spreading are limited due to experimental difficulties arising from microdroplet manipulation and substrate wettability control. For droplet sizes approaching the capillary length scale, the gravitational force plays an important rol...

Discrete-packaged wide bandgap (WBG) semiconductor devices provide a flexible and cost-effective solution for scalable highly dense power electronics. However, their utilization at high power levels is limited due to various challenges, while the effective thermal management if one of them. We develop a liquid cooled thermal management solution for...

Power densification and rising module heat losses cannot be managed by traditional "external-to-case" cooling solutions. This is especially pronounced in high voltage systems, where intervening layers of insulating material between the power devices and cooling solution need to be sufficiently thick to provide adequate voltage isolation. As operati...

Opportunities and value of dropwise condensation of steam. Suggested improvements to a steam plant to enhance efficiency. The red box highlights the opportunity for improvement by designing condenser to decrease turbine back‐pressure. Adapted from Ref 1 in the paper.

High power electronics are a key component in the electrification of aircraft. Large amounts of power need to be handled onboard to generate sufficient lift for flight. The transient nature of the aircraft's mission profile produces varied loading and environmental influences, making consistent cooling and device reliability difficult to maintain....

Dropwise condensation has received extensive interest due to its potential to enhance the efficiency of power generation, water harvesting, and thermal management systems. The degree of heat transfer enhancement during dropwise condensation is hindered by the delicate balance between nucleation, droplet growth rate, and condensate shedding. Condens...

Measuring condensation heat transfer and its associated heat transfer coefficient is not trivial. Rigorous measurements require careful experimental design and tradeoff studies to properly select sensor type, sample geometry and size, coolant fluid and flow rate, operating conditions, working fluid purity, purge methodology, and measurement protoco...