Applications of Microfluidic Devices in Food Engineering

Microfluidics in smart food safety

The evolution of food safety practices is crucial in addressing the challenges posed by a growing global population and increasingly complex food supply chains. Traditional methods are often labor-intensive, time-consuming, and susceptible to human error. This chapter explores the transformative potential of integrating microfluidics into smart food safety protocols. Microfluidics, involving the manipulation of small fluid volumes within microscale channels, offers a sophisticated platform for developing miniaturized devices capable of complex tasks. Combined with sensors, actuators, big data analytics, artificial intelligence, and the Internet of Things, smart microfluidic systems enable real-time data acquisition, analysis, and decision-making. These systems enhance control, automation, and adaptability, making them ideal for detecting contaminants, pathogens, and chemical residues in food products. The chapter covers the fundamentals of microfluidics, its integration with smart technologies, and its applications in food safety, addressing the challenges and future directions in this field.

Paper-based sensors: affordable, versatile, and emerging analyte detection platforms

Paper-based sensors, often referred to as paper-based analytical devices (PADs), stand as a transformative technology in the field of analytical chemistry. They offer an affordable, versatile, and accessible solution for diverse analyte detection. These sensors harness the unique properties of paper substrates to provide a cost-effective and adaptable platform for rapid analyte detection, spanning chemical species, biomolecules, and pathogens. This review highlights the key attributes that make paper-based sensors an attractive choice for analyte detection. PADs demonstrate their versatility by accommodating a wide range of analytes, from ions and gases to proteins, nucleic acids, and more, with customizable designs for specific applications. Their user-friendly operation and minimal infrastructure requirements suit point-of-care diagnostics, environmental monitoring, food safety, and more. This review also explores various fabrication methods such as inkjet printing, wax printing, screen printing, dip coating, and photolithography. Incorporating nanomaterials and biorecognition elements promises even more sophisticated and sensitive applications.

Navigating the future: Microfluidics charting new routes in drug delivery

Microfluidics has emerged as a transformative force in the field of drug delivery, offering innovative avenues to produce a diverse range of nano drug delivery systems. Thanks to its precise manipulation of small fluid volumes and its exceptional command over the physicochemical characteristics of nanoparticles, this technology is notably able to enhance the pharmacokinetics of drugs. It has initiated a revolutionary phase in the domain of drug delivery, presenting a multitude of compelling advantages when it comes to developing nanocarriers tailored for the delivery of poorly soluble medications. These advantages represent a substantial departure from conventional drug delivery methodologies, marking a paradigm shift in pharmaceutical research and development. Furthermore, microfluidic platformsmay be strategically devised to facilitate targeted drug delivery with the objective of enhancing the localized bioavailability of pharmaceutical substances. In this paper, we have comprehensively investigated a range of significant microfluidic techniques used in the production of nanoscale drug delivery systems. This comprehensive review can serve as a valuable reference and offer insightful guidance for the development and optimization of numerous microfluidics-fabricated nanocarriers.

Deep learning-augmented T-junction droplet generation

Droplet generation technology has become increasingly important in a wide range of applications, including biotechnology and chemical synthesis. T-junction channels are commonly used for droplet generation due to their integration capability of a larger number of droplet generators in a compact space. In this study, a finite element analysis (FEA) approach is employed to simulate droplet production and its dynamic regimes in a T-junction configuration and collect data for post-processing analysis. Next, image analysis was performed to calculate the droplet length and determine the droplet generation regime. Furthermore, machine learning (ML) and deep learning (DL) algorithms were applied to estimate outputs through examination of input parameters within the simulation range. At the end, a graphical user interface (GUI) was developed for estimation of the droplet characteristics based on inputs, enabling the users to preselect their designs with comparable microfluidic configurations within the studied range.

Flow Ripple Reduction in Reciprocating Pumps by Multi-Phase Rectification

Reciprocating piezoelectric micropumps enable miniaturization in microfluidics for lab-on-a-chip applications such as organs-on-chips (OoC). However, achieving a steady flow when using these micropumps is a significant challenge because of flow ripples in the displaced liquid, especially at low frequencies or low flow rates (<50 µL/min). Although dampers are widely used for reducing ripples in a flow, their efficiency depends on the driving frequency of the pump. Here, we investigated multi-phase rectification as an approach to minimize ripples at low flow rates by connecting piezoelectric micropumps in parallel. The efficiency in ripple reduction was evaluated with an increasing number (n) of pumps connected in parallel, each actuated by an alternating voltage waveform with a phase difference of 2π/n (called multi-phase rectification) at a chosen frequency. We introduce a fluidic ripple factor (RFfl.), which is the ratio of the root mean square (RMS) value of the fluctuations present in the rectified output to the average fluctuation-free value of the discharge flow, as a metric to express the quality of the flow. The fluidic ripple factor was reduced by more than 90% by using three-phase rectification when compared to one-phase rectification in the 2-60 μL/min flow rate range. Analytical equations to estimate the fluidic ripple factor for a chosen number of pumps connected in parallel are presented, and we experimentally confirmed up to four pumps. The analysis shown can be used to design a frequency-independent multi-phase fluid rectifier to the desired ripple level in a flow for reciprocating pumps.

Parameter control, characterization and stability of soy protein emulsion prepared by microfluidic technology

A flow-focusing microfluidic device driven by pressure was employed in soy protein emulsions with uniform droplet size and good morphology. The results suggested that pressure was an essential factor for droplet formation. The optimum parameter was at a continuous phase pressure of 140 mbar and dispersed phase pressure of 80 mbar. Under this condition, the droplet formation time was shortened to 0.20 s, with average sizes of 39-43 μm and coefficient of variation of about 2 %. Emulsion stability was improved with increasing soy protein isolate (SPI) concentrations. At SPI concentrations higher than 20 mg/mL, the emulsions exhibited improved stability against changes in temperature, pH and salt concentration. Emulsions prepared in this manner exhibited superior oxidative stability than those prepared by conventional methods utilizing homogenizers. This study showed that microfluidic technology can be applied to soy protein emulsions as an effective tool for preparing droplets with uniform size and enhanced stability.

Simulation, analysis, fabrication and characterization of tunable AAO membrane for microfluidic filtration

Microfluidic filtration is an essential process in many biomedical applications. Micro or nanoporous membranes are used for colloidal retention. During the membrane filtration process visualization of various phenomena is challenging. Theoretical models have been proposed to visualize the transport mechanism. In this work, ANSYS Fluent is used for 3D designing of the microfluidic system and Fuzzy simulations are used to study flow rate and velocity, to get the maximum benefit from Anodized Aluminium oxide membrane in practical applications. The proposed method exploits relations between driving force, membrane area, and fluid flow. After optimization of parameters for the filtration, the AAO membrane with desired pore diameter was fabricated using the two-step anodization method. Scanning electron microscope is used for characterization of fabricated AAO membrane. The simulated and theoretical results using computer-based programs are then compared for manipulation of flow rate during the filtration process. Along with the manipulation of flow rate from nanoporous membrane other challenges faced during the filtration process are also highlighted with possible solutions.

Emulsion characterization via microfluidic devices: A review on interfacial tension and stability to coalescence

Emulsions have gained significant importance in many industries including foods, pharmaceuticals, cosmetics, health care formulations, paints, polymer blends and oils. During emulsion generation, collisions can occur between newly-generated droplets, which may lead to coalescence between the droplets. The extent of coalescence is driven by the properties of the dispersed and continuous phases (e.g. density, viscosity, ion strength and pH), and system conditions (e.g. temperature, pressure or any external applied forces). In addition, the diffusion and adsorption behaviors of emulsifiers which govern the dynamic interfacial tension of the forming droplets, the surface potential, and the duration and frequency of the droplet collisions, contribute to the overall rate of coalescence. An understanding of these complex behaviors, particularly those of interfacial tension and droplet coalescence during emulsion generation, is critical for the design of an emulsion with desirable properties, and for the optimization of the processing conditions. However, in many cases, the time scales over which these phenomena occur are extremely short, typically a fraction of a second, which makes their accurate determination by conventional analytical methods extremely challenging. In the past few years, with advances in microfluidic technology, many attempts have demonstrated that microfluidic systems, characterized by micrometer-size channels, can be successfully employed to precisely characterize these properties of emulsions. In this review, current applications of microfluidic devices to determine the equilibrium and dynamic interfacial tension during droplet formation, and to investigate the coalescence stability of dispersed droplets applicable to the processing and storage of emulsions, are discussed.

Computer simulation of submicron fluid flows in microfluidic chips and their applications in food analysis

In recent years, countries around the world have maintained a zero-tolerance attitude toward safety problems in the food industry. In order to ensure human health, a fast, sensitive, and high-throughput analysis of food contaminants is necessary to ensure safe food products on the market. Microfluidics, as a high-efficiency and sensitive detection technology, has many advantages in the detection of food contaminants, including foodborne pathogens, pesticides, heavy metal ions, toxic substances, and so forth, especially in conjunction with a variety of submicron fluid driving methods, making food detection and analysis more efficient and accurate. This review introduces the principle of submicron fluid driving modes and discusses the driving simulation of submicron fluid in microfluidic chips. In addition, the latest developments in the application of simulation in food analysis from 2006 to 2020 are discussed, and the computer simulation of submicron fluid flow in microfluidic chips and its application and development trend in food analysis are also highlighted. The review indicates that microfluidic technology, using numerical simulation as an auxiliary tool, combined with traditional methods has greatly improved the detection and analysis of food products. In addition, microfluidics combined with a variety of control methods embodies the ability of specific, multifunctional, and sensitive detection and analysis of food products. The development of high-sensitivity, high-throughput, portable, integrated microfluidic chips will enable the technology to be applied in practice.

Texture-Modified Food for Dysphagic Patients: A Comprehensive Review

Food texture is a major food quality parameter. The physicochemical properties of food changes when processed in households or industries, resulting in modified textures. A better understanding of these properties is important for the sensory and textural characteristics of foods that target consumers of all ages, from children to the elderly, especially when food product development is considered for dysphagia. Texture modifications in foods suitable for dysphagic patients will grow as the numbers of elderly citizens increase. Dysphagia management should ensure that texture-modified (TM) food is nutritious and easy to swallow. This review addresses how texture and rheology can be assessed in the food industry by placing particular emphasis on dysphagia. It also discusses how the structure of TM food depends not only on food ingredients, such as hydrocolloids, emulsifiers, and thickening and gelling agents, but also on the applied processing methods, including microencapsulation, microgels as delivery systems, and 3D printing. In addition, we address how to modify texture for individuals with dysphagia in all age groups, and highlight different strategies to develop appropriate food products for dysphagic patients.

Application of microfluidic technology in food processing

Microfluidic technology is interdisciplinary with a diversity of applications including in food processing. The rapidly growing global population demands more advanced technologies in food processing to produce more functional and safer food, and for such processing microfluidic devices are a popular choice. This review critically critiques the state-of-the-art designs of microfluidic devices and their applications in food processing, and identifies the key research trends and future research directions for maximizing the value of microfluidic technology. Capillary, planar, and terrace droplet generation systems are currently used in the design of microfluidic devices, each with their strengths and weaknesses as applied in food processing, for emulsification, food safety measurements, and bioactive compound extraction. Conventional channel-based microfluidic devices are prone to clogging, and have high labor costs and low productivity, and their "directional pressure" restricts scaling-up capabilities. These disadvantages can be overcome by using "inside-out centrifugal force" and the new generation continuous flow thin-film microfluidic Vortex Fluidic Device (VFD) which facilitates translating laboratory processing into commercial products. Also highlighted is controlling protein-polysaccharide interactions and the applications of the produced ingredients in food formulations as targets for future development in the field.

Fabrication and Applications of Microfluidic Devices: A Review

Microfluidics is a relatively newly emerged field based on the combined principles of physics, chemistry, biology, fluid dynamics, microelectronics, and material science. Various materials can be processed into miniaturized chips containing channels and chambers in the microscale range. A diverse repertoire of methods can be chosen to manufacture such platforms of desired size, shape, and geometry. Whether they are used alone or in combination with other devices, microfluidic chips can be employed in nanoparticle preparation, drug encapsulation, delivery, and targeting, cell analysis, diagnosis, and cell culture. This paper presents microfluidic technology in terms of the available platform materials and fabrication techniques, also focusing on the biomedical applications of these remarkable devices.

Lateral migration of a ferrofluid droplet in a plane Poiseuille flow under uniform magnetic fields

The lateral migration of a two-dimensional (2D) viscous ferrofluid droplet in a plane Poiseuille flow under a uniform magnetic field is studied numerically by using the level set method. Focusing on low droplet Reynolds number flows (Re_{d}≤0.05), several numerical simulations are carried out to analyze the effects of magnetic field direction and strength, droplet size, and viscosity ratio on the lateral migration behavior of the droplet. The results indicate that the magnetic field direction plays a pivotal role in the trajectory of lateral migration of the droplet and the final equilibrium position in the channel. When the magnetic field is parallel to the channel, i.e., α=0^{∘} (the direction of magnetic field), the droplet is found to settle closer to the wall with an increase in magnetic Bond number Bo_{m}, while at α=45^{∘}, the droplet settles closer to the channel center. Varying the initial droplet sizes at a fixed magnetic Bond number Bo_{m} and viscosity ratio λ results in different final equilibrium positions within the channel. Additionally, the effect of different viscosity ratios on the migration behavior of the droplet is examined at variable magnetic Bond numbers Bo_{m}. At α=45^{∘}, a critical steady state of deformation is found for λ=0.5 and 1 where the droplet changes its migration direction and shifts toward the center of the channel, while at λ=0.05, the droplet crosses the center. At α=90^{∘}, the droplet is found to settle exactly at the center of the flow domain irrespective of different magnetic Bond numbers, droplet sizes, and viscosity ratios.

Application of Microfluidics in the Production and Analysis of Food Foams

Emulsifiers play a key role in the stabilization of foam bubbles. In food foams, biopolymers such as proteins are contributing to long-term stability through several effects such as increasing bulk viscosity and the formation of viscoelastic interfaces. Recent studies have identified promising new stabilizers for (food) foams and emulsions, for instance biological particles derived from water-soluble or water-insoluble proteins, (modified) starch as well as chitin. Microfluidic platforms could provide a valuable tool to study foam formation on the single-bubble level, yielding mechanistic insights into the formation and stabilization (as well as destabilization) of foams stabilized by these new stabilizers. Yet, the recent developments in microfluidic technology have mainly focused on emulsions rather than foams. Microfluidic devices have been up-scaled (to some extent) for large-scale emulsion production, and also designed as investigative tools to monitor interfaces at the (sub)millisecond time scale. In this review, we summarize the current state of the art in droplet microfluidics (and, where available, bubble microfluidics), and provide a perspective on the applications for (food) foams. Microfluidic investigations into foam formation and stability are expected to aid in optimization of stabilizer selection and production conditions for food foams, as well as provide a platform for (large-scale) production of monodisperse foams.

Effects of wall velocity slip on droplet generation in microfluidic T-junctions

The effect of the slip lengths of both continuous and dispersed phases on droplet formation in microfluidic T-junctions is investigated by a volume of fluid method. Results reveal that, in a dripping regime, the droplet size is mainly influenced by the slip length of the continuous phase and increases with it. In a squeezing regime, the droplet size decreases with the slip lengths of both phases. The effects of the slip lengths of both phases on droplet generation are systematically discussed and summarized. The elongation rate of the thread can be decreased with an increase of slip lengths in both dripping and squeezing regimes, which is beneficial to improve droplet monodispersity. The monodispersity of droplets can deteriorate when the slip length of either phase is small and can be improved by increasing the slip length of the other phase.

Wall velocity slip can significantly affect droplet generation in droplet-based microfluidics.

Spontaneous Selective Preconcentration Leveraged by Ion Exchange and Imbibition through Nanoporous Medium

Manipulating mechanism of particle’s motion has been extensively studied for the sample preparation in microfluidic applications including diagnostics, food industries, biological analyses and environmental monitoring. However, most of conventional methods need additional external forces such as electric field or pressure and complicated channel designs, which demand highly complex fabrication processes and operation strategies. In addition, these methods have inherent limitations of dilution or mixing during separation or preconcentration step, respectively, so that a number of studies have reported an efficient selective preconcentration process, i.e. conducting the separation and preconcentration simultaneously. In this work, a power-free spontaneous selective preconcentration method was suggested based on leveraging convective flow over diffusiophoresis near the water-absorbing nanoporous ion exchange medium, which was verified both by simulation and experiment. Especially, the velocity of the convective flow by an imbibition deviated from the original tendency of t^−1/2 due to non-uniformly patterned nanoporous medium that has multiple cross-sectional areas. As a result, the direction of particle’s motion was controlled at one’s discretion, which led to the spontaneous selective preconcentration of particles having different diffusiophoretic constant. Also, design rule for maximizing the efficiency was recommended. Thus, this selective preconcentration method would play as a key mechanism for power-free lab on a chip applications.

Fab on a Package: LTCC Microfluidic Devices Applied to Chemical Process Miniaturization

Microfluidics has brought diverse advantages to chemical processes, allowing higher control of reactions and economy of reagents and energy. Low temperature co-fired ceramics (LTCC) have additional advantages as material for fabrication of microfluidic devices, such as high compatibility with chemical reagents with typical average surface roughness of 0.3154 μm, easy scaling, and microfabrication. The conjugation of LTCC technology with microfluidics allows the development of micrometric-sized channels and reactors exploiting the advantages of fast and controlled mixing and heat transfer processes, essential for the synthesis and surface functionalization of nanoparticles. Since the chemical process area is evolving toward miniaturization and continuous flow processing, we verify that microfluidic devices based on LTCC technology have a relevant role in implementing several chemical processes. The present work reviews various LTCC microfluidic devices, developed in our laboratory, applied to chemical process miniaturization, with different geometries to implement processes such as ionic gelation, emulsification, nanoprecipitation, solvent extraction, nanoparticle synthesis and functionalization, and emulsion-diffusion/solvent extraction process. All fabricated microfluidics structures can operate in a flow range of mL/min, indicating that LTCC technology provides a means to enhance micro- and nanoparticle production yield.

Study on the Optimum Cutting Parameters of an Aluminum Mold for Effective Bonding Strength of a PDMS Microfluidic Device

Master mold fabricated using micro milling is an easy way to develop the polydimethylsiloxane (PDMS) based microfluidic device. Achieving high-quality micro-milled surface is important for excellent bonding strength between PDMS and glass slide. The aim of our experiment is to study the optimal cutting parameters for micro milling an aluminum mold insert for the production of a fine resolution microstructure with the minimum surface roughness using conventional computer numerical control (CNC) machine systems; we also aim to measure the bonding strength of PDMS with different surface roughnesses. Response surface methodology was employed to optimize the cutting parameters in order to obtain high surface smoothness. The cutting parameters were demonstrated with the following combinations: 20,000 rpm spindle speed, 50 mm/min feed rate, depth of cut 5 µm with tool size 200 µm or less; this gives a fine resolution microstructure with the minimum surface roughness and strong bonding strength between PDMS–PDMS and PDMS–glass.

Paper-based analytical devices for clinical diagnosis: recent advances in the fabrication techniques and sensing mechanisms

INTRODUCTION

There is a significant interest in developing inexpensive portable biosensing platforms for various applications including disease diagnostics, environmental monitoring, food safety, and water testing at the point-of-care (POC) settings. Current diagnostic assays available in the developed world require sophisticated laboratory infrastructure and expensive reagents. Hence, they are not suitable for resource-constrained settings with limited financial resources, basic health infrastructure, and few trained technicians. Cellulose and flexible transparency paper-based analytical devices have demonstrated enormous potential for developing robust, inexpensive and portable devices for disease diagnostics. These devices offer promising solutions to disease management in resource-constrained settings where the vast majority of the population cannot afford expensive and highly sophisticated treatment options. Areas covered: In this review, the authors describe currently developed cellulose and flexible transparency paper-based microfluidic devices, device fabrication techniques, and sensing technologies that are integrated with these devices. The authors also discuss the limitations and challenges associated with these devices and their potential in clinical settings. Expert commentary: In recent years, cellulose and flexible transparency paper-based microfluidic devices have demonstrated the potential to become future healthcare options despite a few limitations such as low sensitivity and reproducibility.

Convex Grooves in Staggered Herringbone Mixer Improve Mixing Efficiency of Laminar Flow in Microchannel

The liquid streams in a microchannel are hardly mixed to form laminar flow, and the mixing issue is well described by a low Reynolds number scheme. The staggered herringbone mixer (SHM) using repeated patterns of grooves in the microchannel have been proved to be an efficient passive micro-mixer. However, only a negative pattern of the staggered herringbone mixer has been used so far after it was first suggested, to the best of our knowledge. In this study, the mixing efficiencies from negative and positive staggered herringbone mixer patterns as well as from opposite flow directions were tested to investigate the effect of the micro-structure geometry on the surrounding laminar flow. The positive herringbone pattern showed better mixing efficiency than the conventionally used negative pattern. Also, generally used forward flow gives better mixing efficiency than reverse flow. The mixing was completed after two cycles of staggered herringbone mixer with both forward and reverse flow in a positive pattern. The traditional negative pattern showed complete mixing after four and five cycles in forward and reverse flow direction, respectively. The mixing effect in all geometries was numerically simulated, and the results confirmed more efficient mixing in the positive pattern than the negative. The results can further enable the design of a more efficient microfluidic mixer, as well as in depth understanding of the phenomena of positive and negative patterns existing in nature with regards to the surrounding fluids.

Spatial Site-Patterning of Wettability in a Microcapillary Tube

Substrate functionalization is of great importance in successfully manipulating flows and liquid interfaces in microdevices. Herein, we propose an alternative approach for spatial patterning of wettability in a microcapillary tube. The method combines a photolithography process with self-assembled monolayer formation. The modified microcapillaries show very sharp boundaries between the alternating hydrophilic/hydrophobic segments with an achieved smallest domain dimension down to 60 μm inside a 580 μm inner diameter capillary. Our two-step method allows us to pattern multiple types of functional groups in an enclosed channel. Such structures are promising regarding the manipulation of segmented flows inside capillaries.

Patterning microfluidic device wettability with spatially-controlled plasma oxidation

Microfluidic devices can form double emulsions with uniform properties, but require cumbersome fabrication steps to pattern their wettability. We demonstrate spatially-controlled plasma oxidation to create wettability patterns for forming double emulsions. Our method performs comparably to chemical techniques but is simpler, more reliable, and scalable to patterning large arrays of drop makers.

Bubbles and foams in microfluidics

Microfluidics offers great tools to produce highly-controlled dispersions of gas into liquid, from isolated bubbles to organized microfoams. Potential technological applications are manifold, from novel materials to scaffolds for tissue engineering or enhanced oil recovery. More fundamentally, microfluidics makes it possible to investigate the physics of complex systems such as foams at scales where the capillary forces become dominant, in model experiments involving few well-controlled parameters. In this context, this review does not have the ambition to detail in a comprehensive manner all the techniques and applications involving bubbles and foams in microfluidics. Rather, it focuses on particular consequences of working at the microscale, under confinement, and hopes to provide insight into the physics of such systems. The first part of this work focuses on bubbles, and more precisely on (i) bubble generation, where the confinement can suppress capillary instabilities while inertial effects may play a role, and (ii) bubble dynamics, paying special attention to the lubrication film between bubble and wall and the influence of confinement. The second part addresses the formation and dynamics of microfoams, emphasizing structural differences from macroscopic foams and the influence of the confinement.

Three-dimensional parallelization of microfluidic droplet generators for a litre per hour volume production of single emulsions

This paper looks at the design, fabrication and characterization of stackable microfluidic emulsion generators, with coefficients of variation as low as ~6% and with production rates as high as ~1 L h(-1). This work reports the highest throughput reported in the literature for a microfluidic device with simultaneous operation of liquid-liquid droplet generators. The device was achieved by stacking several layers of 128 flow-focusing droplet generators, organized in a circular array. These layers are interconnected via through-holes and fed with designated fractal distribution networks. The proposed layers were milled on poly(methylmethacrylate) (PMMA) sheets and the stack was thermo-compression bonded to create a three-dimensional device with a high density of generators and an integrated hydraulic manifold. The effect of stacking multiple layers was studied and the results show that fabrication accuracy has a greater impact on the dispersity of the emulsion than the addition of more layers to the stack. Particle crystallization of drugs was also demonstrated as a possible application of this technology in industry.

Conventional and Innovative Processing of Milk for Yogurt Manufacture; Development of Texture and Flavor: A Review

Milk and yogurt are important elements of the human diet, due to their high nutritional value and their appealing sensory properties. During milk processing (homogenization, pasteurization) and further yogurt manufacture (fermentation) physicochemical changes occur that affect the flavor and texture of these products while the development of standardized processes contributes to the development of desirable textural and flavor characteristics. The processes that take place during milk processing and yogurt manufacture with conventional industrial methods, as well as with innovative methods currently proposed (ultra-high pressure, ultrasound, microfluidization, pulsed electric fields), and their effect on the texture and flavor of the final conventional or probiotic/prebiotic products will be presented in this review.

Microfluidic production of spherical and nonspherical fat particles by thermal quenching of crystallizable oils

We report the microfluidic production of spherical and nonspherical fat particles from crystallizable oils. The method is based on microfluidic generation of oil droplets at a cross-junction followed by thermal solidification downstream in a microcapillary. We vary the drop production conditions and the device temperature and demonstrate that the size, shape, and crystallinity can be controlled. By measuring thermal gradients in the microcapillary, we show that crystalline fat particles are best produced when the device temperature is below the onset temperature of bulk fat crystallization. To produce monodisperse nonspherical fat particles, we find that the carrier fluid flow rate needs to be sufficiently high to provide strong hydrodynamic forces to transport the confined rod-like particles. We identify the scaling relationship between geometric confinement and particle elasticity necessary to maintain the nonspherical shape. Thus, our study provides guidelines for the production of spherical and nonspherical fat particles that can be potentially used for controlling microstructure, rheology, and drug encapsulation in foods, cosmetics, and pharmaceutical creams that employ crystallizable oils.

Optofluidic opportunities in global health, food, water and energy

Optofluidics is a rapidly advancing field that utilizes the integration of optics and microfluidics to provide a number of novel functionalities in microsystems. In this review, we discuss how this approach can potentially be applied to address some of the greatest challenges facing both the developing and developed world, including healthcare, food shortages, malnutrition, water purification, and energy. While medical diagnostics has received most of the attention to date, here we show that some other areas can also potentially benefit from optofluidic technology. Whenever possible we briefly describe how microsystems are currently used to address these problems and then explain why and how optofluidics can provide better solutions. The focus of the article is on the applications of optofluidic techniques in low-resource settings, but we also emphasize that some of these techniques, such as those related to food production, food safety assessment, nutrition monitoring, and energy production, could be very useful in well-developed areas as well.

Green microfluidics made of corn proteins

Petroleum-based polymer such as Poly(dimethylsiloxane) has been widely used to make mesoscale and microscale fluidic devices. The main drawback of such devices in disposable applications is the potential environmental pollution since they are not biodegradable. Biodegradable microfluidic devices have been fabricated out of zein, a prolamin protein found in corn, that can be utilized as disposable health and environmental-friendly micro-chips. Using stereo lithography and soft lithography, micro-chambers and micro-channels features have been replicated on zein films and enclosed zein microfluidic devices are created by bonding to glass substrate using a simple vapor-deposition method. The bonding strength of the zein microfluidic devices has been found to exceed the tensile strength of the zein film and hydraulic pressure, and fluid flow through large-area complex microfluidic designs shows no leakage or distortion. High optical clarity and fluorescent imaging in the zein microfluidic devices are demonstrated by visualizing micro-particles and Rhodamine B. Zein microfluidic devices enable truly disposable microfluidics with intrinsic biocompatibility and biodegradability that can be fabricated using existing techniques.

Suspension flow in microfluidic devices--a review of experimental techniques focussing on concentration and velocity gradients

Microfluidic devices are an emerging technology for processing suspensions in e.g. medical applications, pharmaceutics and food. Compared to larger scales, particles will be more influenced by migration in microfluidic devices, and this may even be used to facilitate segregation and separation. In order to get most out of these completely new technologies, methods to experimentally measure (or compute) particle migration are needed to gain sufficient insights for rational design. However, the currently available methods only allow limited access to particle behaviour. In this review we compare experimental methods to investigate migration phenomena that can occur in microfluidic systems when operated with natural suspensions, having typical particle diameters of 0.1 to 10 μm. The methods are used to monitor concentration and velocity profiles of bidisperse and polydisperse suspensions, which are notoriously difficult to measure due to the small dimensions of channels and particles. Various methods have been proposed in literature: tomography, ultrasound, and optical analysis, and here we review and evaluate them on general dimensionless numbers related to process conditions and channel dimensions. Besides, eleven practical criteria chosen such that they can also be used for various applications, are used to evaluate the performance of the methods. We found that NMR and CSLM, although expensive, are the most promising techniques to investigate flowing suspensions in microfluidic devices, where one may be preferred over the other depending on the size, concentration and nature of the suspension, the dimensions of the channel, and the information that has to be obtained. The paper concludes with an outlook on future developments of measurement techniques.

Droplet based microfluidics

Droplet based microfluidics is a rapidly growing interdisciplinary field of research combining soft matter physics, biochemistry and microsystems engineering. Its applications range from fast analytical systems or the synthesis of advanced materials to protein crystallization and biological assays for living cells. Precise control of droplet volumes and reliable manipulation of individual droplets such as coalescence, mixing of their contents, and sorting in combination with fast analysis tools allow us to perform chemical reactions inside the droplets under defined conditions. In this paper, we will review available drop generation and manipulation techniques. The main focus of this review is not to be comprehensive and explain all techniques in great detail but to identify and shed light on similarities and underlying physical principles. Since geometry and wetting properties of the microfluidic channels are crucial factors for droplet generation, we also briefly describe typical device fabrication methods in droplet based microfluidics. Examples of applications and reaction schemes which rely on the discussed manipulation techniques are also presented, such as the fabrication of special materials and biophysical experiments.

Pet food safety: a shared concern

The safety of the food supply is a subject of intense interest to consumers, particularly as a result of large-scale outbreaks that involve hundreds and sometimes thousands of consumers. During the last decade, this concern about food safety has expanded to include the diets of companion animals as a result of several incidences of chemical toxicities and infectious disease transmission. This has led to increased research into the causes and controls for these hazards for both companion animals and their owners. The following summary provides an introduction to the issues, challenges and new tools being developed to ensure that commercial pet foods are both nutritious and safe.

Microfluidics for food, agriculture and biosystems industries

Microfluidics, a rapidly emerging enabling technology has the potential to revolutionize food, agriculture and biosystems industries. Examples of potential applications of microfluidics in food industry include nano-particle encapsulation of fish oil, monitoring pathogens and toxins in food and water supplies, micro-nano-filtration for improving food quality, detection of antibiotics in dairy food products, and generation of novel food structures. In addition, microfluidics enables applications in agriculture and animal sciences such as nutrients monitoring and plant cells sorting for improving crop quality and production, effective delivery of biopesticides, simplified in vitro fertilization for animal breeding, animal health monitoring, vaccination and therapeutics. Lastly, microfluidics provides new approaches for bioenergy research. This paper synthesizes information of selected microfluidics-based applications for food, agriculture and biosystems industries.