Research

Microfluidics for material production

We develop methods to create new functional materials using microfluidic devices. These devices provide capabilities for very precisely mixing fluids to form new materials. All the structures are based on drops which can both encapsulate active materials and serve as templates on which to build new structures. These have interesting properties and great technological potential for encapsulation and controlled release of a wide variety of active materials. We also consider methods to scale up the fabrication of these materials to produce practical quantities. This work is motivated by both fundamental studies and the potential for creating technologically valuable materials, and some of the work has led to industrial applications.

Some current projects from our group

Microfluidic encapsulation of mesenchymal stem cells in alginate hydrogels

Mesenchymal stem cells (MSCs) are a type of stem cells derived from bone marrow, umbilical cord and a few other tissues. Due to their wide therapeutic potential in tissue regeneration and immunoregulation, MSCs are currently regarded as the most promising candidate for new stem cell therapy. Some clinical experiments have shown promising results when using MSCs to treat systemic immune diseases. Despite their outstanding performance in some studies, consistent efficacy of MSC therapy is still hard to achieve. One of the biggest challenges that hinders the approval of MSC therapy is the short persistence time of MSCs in the host body. After administration in the host body, MSCs are usually lost within 2-3 days. This early cell loss is due to the lack of proper mechanical signaling during the transplantation process, as well as the attack of the host’s immune system. To overcome these problems, we develop microfluidics-based live cell encapsulation strategies to provide the injected cells with an extracellular substrate which at the same time can serve as a layer of protection against the host’s immune system. According to the required administration route, we can perform single- or multi-cell encapsulation in hydrogels of various structures and mechanical properties. Subcutaneous injection of MSC-encapsulating alginate microcapsules made with our method have shown promising persistence time in mouse experiments. Anqi Chen

Photodegradable hydrogel capsules for cell sorting

Hydrogel capsules are core-shell structures that have a liquid core encased in a solid shell. The shell is made from a semi-permeable hydrogel, allowing for the separation of the encapsulated targets while still permitting the exchange of small molecules with the surrounding environment. These capsules are excellent for isolating cells within picoliter- or nanoliter-sized compartments, which facilitates culturing and selection at the individual cell level. Using microfluidic techniques, these capsules can be produced in the millions, making them ideal for high-throughput screening. The durability of the hydrogel shell also supports cell sorting using standard commercial cell sorters. Once sorted, cells within the capsule can be safely released through brief UV exposure without any damage. Wentao Xu

Cell Jamming on Curved Surfaces

During bronchospasms for asthma patients, the cylindrical airway in the longs contracts and compresses which may or may not induce cell jamming and unjamming in the local epithelium. This research project focuses on studying the effects of compression on jammed cells attached to the lumen of a biocompatible tubular hydrogel. This is accomplished by building a 3-dimensional cellular environment that models the asthmatic airway where compressive stress can be applied on the cells to visualize changes in cell shape and arrangement. Using 3D extrusion bioprinting, a biomimetic hydrogel ECM is cast over a printed sacrificial tube in a soft gasket and connected to outlet tubing where perfusion of the tube empties the channel for cells to then occupy for imaging. This will serve as a tool for characterizing airway compression and subsequent cell jamming effects on cell health and mobility. Bobby Haney

Project abstract – Nanoparticles for improved delivery efficiency and enhanced therapy effects

Drug delivery vehicles, such as nanoparticles, micelle, and vesicles play an important role in protecting the drugs and achieving the best treatment effect. Our research mainly focuses on designing nanoparticle carriers for improving drug delivery efficiency. There are many factors that influence the transfection efficiency of the drug, such as the nanoparticle’s morphology, composition, shape, and stiffness. We use microfluidic nano participation to design nanoparticles with uniform size and shape, such as the sphere, dimer, and trimer nanoparticles, The morphology of nanoparticles is modified by antibody, protein, and polysaccharide to improve the cell uptake efficiency. We investigate the relationship between the transfection efficiency of drugs and the design of nanoparticles. These nanoparticles with tunable shapes will provide an important platform to load diverse drugs for improved drug delivery and enhanced clinical therapy. Chenjing Yang, Chunhuan Liu, Tiffany Chen

Cell Behavior at Bone-to-Tendon interface in 3D Cell Culture

At the enthesis, because tendon cells have high alignment in a single direction, while bone cells have no specific orientation, the shared cellular environment is naturally anisotropic. In this work, a hydrogel scaffold with tunable stiffness is created using UV and ionically curable polymer solutions. Using cellulose fibers to implement alignment, crosslinked polymer networks with modulus and alignment gradients can be formed to simulate the complexity of the tendon-bone interface. The scaffolds are seeded with tendon and bone cells to monitor the formation of the natural ECM in response to mechanical and structural changes. By studying this system in a 3D matrix as opposed to the commonly used 2D model, it is possible to probe cell proliferation, migration, and viability as a function of hydrogel mechanical properties in an environment with a closer resemblance to the native extracellular matrix. This work aids in determination of the critical factors (matrix modulus, pore size, anisotropy, growth factor localization) that affect cellular response and subsequent bone regeneration at the tendon-to-bone multicellular junction. Bobby Haney

Microparticles for oral and injectable drug delivery

Microcapsules are spherical structures composed of a semi-permeable shell encompassing a liquid core, typically ranging in diameter from a few microns to 1 mm. This core-shell architecture makes microcapsules an ideal carrier for a wide range of biologically active materials, including peptides, enzymes, RNA, cells, and other substances, with high loading capacity. The protective shell serves as an effective barrier, shielding the encapsulated active agents from harsh external environments. Moreover, the separation of the core and shell facilitates precise control over the release rate of the enclosed drug, enabling modulation over periods spanning from hours to months. Yang Wang

Diné tea extract-encapsulating microgels: microfluidics-based fabrication and their antibacterial effects

Navajo teas or herbs have been used by Native American people to treat a variety of ailments, however, there are currently no standardized extraction processes to obtain bioactives from the teas/herbs. Additionally, the unprotected tea/herb extracts have short shelf-stability and are susceptible to degradation under harsh environmental conditions, which limits the application of Navajo teas/herbs in pharmaceutical scenarios. Here we test different extraction conditions to prepare extracts from four types of teas/herbs, including Navajo tea, Yucca root, Juniper and Bear root and use their antibacterial effects as the selection criteria to determine the best extraction conditions. We then encapsulate the tea/herb extracts in microgels made from pectin, a biopolymer extracted from orange peels to test the stability of extracts. We show that all the tested teas and herbs inhibit the growth of Escherichia coli (E.coli). Teas/herbs boiled for a shorter time of 5 minutes have higher antibacterial effects compared to those boiled for 15 or 30 minutes. The encapsulation of teas/herbs in pectin microgels enhanced the antibacterial properties of bear root tea extracts and further effects on stability is undergoing. This work is in collaboration with students from Navajo Technical University. Yan Liu

Activity-Based Gelation of Microdroplets for Ultrahigh-throughput Directed Enzyme Evolution

Model System for Producing Extracellular Vesicles for Drug Delivery

Small membrane bound vesicles, typically smaller than a micron, are naturally secreted by cells in our body. These vesicles, known as extracellular vesicles, play a crucial role in intercellular communication by transporting, protecting, and releasing cargo into the cytoplasm of recipient cells. Their native composition and biological function have inspired their use in drug delivery.

Resembling cells themselves, they possess an asymmetrical bilipid membrane enclosing an aqueous core. This compositional asymmetry confers them more versatility and mechanical stability compared to commonly used vesicles for drug delivery that have a symmetrical lipid membrane. Their asymmetric structure, small size, and biocompatibility make them unique candidates in drug delivery systems that require efficient cellular uptake and release for therapeutic impact. However, their main challenge is to produce these structures efficiently and at a scale small enough to achieve therapeutic effects.

In our lab we use droplet microfluidics to produce these asymmetric structures. Droplet microfluidics can generate multilayered asymmetrical structures resembling vesicles through the creation of multilayered emulsions as templates. This method offers precise control over the size, layer thickness, and composition of each emulsion. By manipulating the composition of each layer, we can generate asymmetrical structures. Currently the field of microfluidics is well established at the micron-scale. The main challenge is to produce these structures on the sub-micron scale. Our lab has developed a new microfluidic device, that enables us to produce sub-micron emulsions that can be used as templates to produce asymmetrical structures that resemble extracellular vesicles. If you are interested in learning more, please feel free to reach out to me at any time. Ryan Garry

Development of biomimetic liposomes with cell membrane proteins for targeted delivery

Liposomes offer a popular platform for drug delivery. Conventional liposomes have a range of attractive properties, including having tunable surface properties and size. How to further endow liposomes more efficient and target? Cell membrane protein-based biomimetic liposomes are designed to mimic natural cells properties and functions and replicate their behavior in vivo. We incorporated the cell membrane protein in the nano-size liposomes by using microfluidic chips. Biomimetic liposomes can retain the unique biological functions of the source cells. Thereby, they can overcome biological roadblocks and to enhance targeting specificity and efficient. We will study the effects of cell membrane protein on the formation and structure of biomimetic liposomes, especially surface, and their interactions with cells. Then we will evaluate the performance and targeting of biomimetic liposomes in drug delivery. Our project will give a meaningful perspective for targeted drug delivery model. Chunhuan Liu, Kevin Jahnke, Chenjing Yang, Tiffany Chen

Chip Design and Automation of Lipid Nanoparticle Synthesis for mRNA Vaccines

Sugar defender

Diabetes and obesity are increasing health problems worldwide. Overconsumption of sugars, such as fructose and glucose in processed foods is one of the major causes for diabetes and obesity. Food companies have been exploring many ways to develop novel food formulations to reduce the sugar uptake for consumers. Synthetic or natural sweeteners are the most used sugar alternative solutions; however, they may change the textures or flavors of the food products. Additionally, recent research shows that some of the sweeteners would lead to chronic health issues as well. Here we propose to use enzyme-based ‘additives’ to incorporate in food formulations. The enzymes are engineered to be stable under acidic gastric conditions and won’t alter the overall taste or texture of the foods. The safety and efficacy of the engineered enzymes are being tested in gut-on-chip and mouse models. This work is in collaboration with Wyss institute and Kraft Heinz food company. Yan Liu

Some previous projects from our group

pH and nutrient responsive microcapsules for small intestine-specific application

We design and develop microcapsules with multi-stimuli responsive characteristics to facilitate oral delivery of sensitive active food supplements to the small intestine. Patients with gastrointestinal disorders suffer from disrupted permeability of intestinal epithelial barrier, leading to impaired nutrient absorption. To restore their adequate uptake of nutrients, we use microfluidic approach to encapsulate food supplements in microcapsules, which have defined stimuli responsive properties as well as tunable intestinal mucosal penetrating and adhesive behaviors. Yan Liu

Cell in gel

Stem cells are becoming one of the most promising forms of therapy in tissue engineering and stem cell therapy due to its differentiation into various types of cells. Stem cell can be collected directly, engineered and injected back into patients as a key component of immunotherapy. However, the efficacy of cell-based therapies depends on materials science. While directly injecting cell into patient, these cells are not very effective in performing their tasks. The vital reason is that the immune cell response from the patient, which makes this process very inefficient. This presents a major impediment to the widespread success of cell-based therapies. Hydrogel is a three-dimensional material possessing pores that large enough to transmit small ions but small enough to block the attack from immune attach. In the lab, we have developed a microfluidic based method that can successfully encapsulate stem cell with minimum damage to the cell, and we study their behavior both in vitro and in vitro. Currently, we can maintain cell viability as high as 99%, and we also design different device to study the cell-cell interaction at single cell level. Moreover, to validate its capability in tissue repair, we delivery the gel encapsulated cells in mouse for the osteogenesis. Liyuan Zhang

Quadruple Emulsion Templated Multilamellar Phospholipid Vesicles

Multilamellar vesicles are promising delivery vehicles for multiple components of drugs or enzymes for pharmaceuticals and cosmetics. There have been reports of multiple polymersomes for encapsulation and programmed release. However, phospholipids as the natural component of biological membranes have not been successfully used for fabrication of multilamellar vesicles, mainly because of their fragility and small size. In this project we want to develop a microfluidic method to prepare liposomes with double bilayers through quadruple emulsion templates. The resultant biocompatible vehicle will have potential application for separated storage and controlled release of multiple components. Moreover, we also look forward to providing a platform to study physical properties of biomembranes with multilamellar liposome structures. Anqi Chen

Encapsulation and enhanced biocidal effect in biodiesel

A major problem delays wide application of biodiesel is microbial contamination during storage. Most of the microbes live in water phase in the storage tank. The most effective way to kill the microbes is to dose biocide directly to the water phase. However practically people put antimicrobial actives to the biodiesel directly, the extra antimicrobial actives will eventually be combusted with the fuel and emitted to the air causing air pollution. We use microfluidic approach to encapsulate biocide in hydrogel, which acts as a vehicle that delivers biocide to the interface of oil and water then burst release the biocide into water, leaving as little as possible biocide in the oil phase. Hao Pei

Fatty amine encapsulation

Fatty amine is a widely used nonionic surfactant for water in oil emulsion. It’s also been added to the marine engine lubricant as the neutralizing active. It’s a type of very effective acid remover but it is instable in high temperature, like working temperature in the engine. We are interested in protecting the fatty amine from early degradation and controllably releasing it in acidic environment. By encapsulating fatty amine in pH-responsive microcapsules, it is possible to use the capsule shell as the physical barrier to separate the air and the inside fatty amine, thus delay the oxidative degradation. Hao Pei

Smart Janus capsules

Microscopic materials with anisotropic structures or compositions are of great interesting and potentials for various applications. My project focus on fabrication of Janus microcapsules with anisotropic structures or compositions by microfluidics, which could be applied to stimulating responsive, drug delivery and microactuators. Yong Zhao

Nanoliposomes, Phospholipid Liposomes, and Polymersomes for Drug Delivery

In order to improve the delivery of drugs to the target area, a number of different capsules for drugs are being developed. The ideal particle will be safe and stable, able to deliver a targeted dose of drug only to treatment areas. Mingtan Hai

Electrically-Controlled Programmable Microfluidics System

You need to prepare for 3 hours and you collect the droplets for 15 minutes, leave along the time designing in AutoCAD, making wafer, and if some are blocked you need to debug and do it again. Have you ever thought about “make it once, run it immediately”? You can do it if you have valves that controllable and connect the elements you want it to. Unlike programmable microfluidics project in Stanford, I use electrically controllable valves that largely facilitate the portability of the device, when study today are all using magnetically controlled or vacuum controlled valves which need abundant hardware and limit its usage; Now we have a 3CM*3CM chip that connect to microfluidics chips and control 3*3 grid of valves by computer, as well as a activator grid for valves comprising 64 addressable electrodes served as valves actuators. The goal of it is to demonstrate an electrically controlled “generous purpose” system comprising elements such as cell trap, channels, mixer, and detection mechanism and connected by valve grid via ipad coding. Yanzhe Qin

Multilayer Polyelectrolyte Capsule Assembly in Microfluidic Device

In the classical Layer-by-Layer (LbL) technique, polyelectrolyte multi-layer capsules are fabricated by alternatively deposited charged polyelectrolytes onto an oppositely bulk or colloidal template followed by dissolved the template which is high consuming. Droplet-based microfluidics which involves the generation of producing high mono-dispersity drops offers a platform for miniaturizing LbL technique by imparting benefits of time and reagent reduction. We present a novel deposition method by designing a new microfluidic coating device which utilizes “Z” shape channel to guide discrete droplets. Similar to the game of pinball in which the templates guided and diverted to the downstream direction smoothly by repeated unit rows of fabricated channels. Right now, we achieved four layers of polyelectrolyte deposition on a template in less than 2 minutes by guiding discrete templates through coating and washing solution of flushing and two polyelectrolytes. Liyuan Zhang

Fabrication of multilayered microfluidic devices and its application for double emulsions

Photolithography is an accurate, reproducible and easy method for fabricating micron scale devices. The basic outcome of Photolithography is a single layer, and it is possible to repeat the exposure process and end up with multilayered landscapes. However, some topologies are impossible to achieve using multiple exposures and require a complementary method of stacking up devices after fabrication. We use a simple method for aligning stacks of micron-scale devices that relies on matching locks and keys that are an inherent part of the device. Applications of multilayered devices are numerous. We focus here on the generation of double emulsions that are useful for instance in encapsulation (drug delivery) and particle synthesis. The formation of double emulsions in single layered microfluidic devices demands precise spatial control over surface properties of the device channels. However in the case of axial symmetric microfluidic devices such as capillaries, this is no longer a constraint since there is no direct contact between the double emulsion and the device surface. We show that forming double emulsions in multilayered microfluidic device is similar to their formation in capillaries, alleviating the need for precise spatial control of wettability. Improving the robustness of double emulsion formation in photolithographic devices is important for large scale uses of double emulsions. Assaf Rotem

Spatially Segregated Wettability in Microfluidic Devices and Scale-up

In order to make water-in-oil-in-water double emulsions with microfluidic devices, the channels of the device must have spatially segregated wettability – in other words the wettability should be such that the first junction of the device wets the shell phase, and the second junction wets the oil phase. We use tandem emulsification to achieve spatially segregated wettability, and also explore methods of achieving segregated wettability in thermoplastic devices through careful engineering of device geometry and functionalization techniques. We also scale-up the production of double emulsions with sizes close to the millimeter-range and with viscous shells, shown here. Saraf Nawar

Encapsulation of neutralizing agents for marine lubricants

Fatty amines (FAs) are used as effective acid neutralizing agents in marine lubricants, however they suffer thermal degradation in marine engine. The goal of this project is to protect FAs from early oxidation and thermal degradation and release them when entering into contact with organic acid. The challenge of encapsulating FAs is that FAs prefer to stay at interface due to very low surface tension. Our strategy is to trap FAs in the crosslinked polymer network as a core and generate protective shells by using pH-responsive polymer. Liangliang Qu

Reversibly responsive and selective microcapsules

Polymeric microgels and microcapsules with temperature triggered property changes have promising applications in the fields of controlled release, cell laden, cosmetics, etc. Till now, PNiPAM is the mostly used polymer for thermoresponsive microparticles fabrication by microfluidics. However, the irreversible phase transition and the ambiguous biocompatibility due to the presence of amide groups in its structures limit its applications. As an alternative, oligoethylene glycol (OEG)-based dendronized polymers have several superior characteristics, including good biocompatibility, excellent antifouling property, fully reversible thermoresponsiveness, tunable LCSTs and switchable shielding effect, which will be used for microparticles fabrication in this project. We aim to develop novel thermoresponsive particles with excellent properties for materials applications. Wen Li

OEG-based thermoresponsive microparticles by microfluidics

Ultrahigh drug loaded carriers

An advanced approach that can precisely control over the preparation process to generate homogeneously size distributed particles with ultrahigh mass fraction of therapeutics, controlled payload release profiles, as well as high throughput productivity is strongly desirable. With the help of microfluidics, I am aiming to develop a versatile and robust approach to efficiently synthesize optimal core/shell structured vectors. After characterization, the obtained optimal vectors will be utilized for cancer therapy or spinal cord injury treatment. Dongfei Liu

“Velcro” Surfactant for Biological Assays Performed in Droplets

To extend the ability to perform biological tests in droplets, we have developed a new, biocompatible surfactant that forms a stabilizing interfacial film on the surface of droplets. Using the surfactant we are able to stabilize drops much more effectively than with existing surfactants. We can use the surfactant to generate extremely large droplets in which we can selectively amplify genetic targets and culture cells. In the future, we will use this surfactant in support of ongoing work categorizing antibody-producing immune cells for the discovery of new therapeutics. Brendan Deveney

Fabrication of functional materials using microfluidics

Materials at microscale have many advantages in biological and biomedical applications, due to their unique size compatibility with cells. My research focuses on using glass capillary microfluidic devices to fabricate various functional materials for bio-applications. By precisely manipulating the fluids using microfluidic technology, I can produce various types of droplets, including single-emulsion droplets and double-emulsion droplets, with controllable size and structures. For example, I prepare poly(ethylene glycol) based microhydrogels using an oil-in-water single emulsion method. These biocompatible microhydrogels can either incorporate hydrophobic drugs with high quantity and homogeneity for drug delivery application, or carry hydrophilic DNA for droplet barcoding for single cell sequencing application. Another example is microcapsules fabricated using a water-in-oil-in-water double emulsion method to encapsulate various valuable biomaterials, such as enzymes and antibodies, for controlled release. Weixia Zhang

Encapsulation and controlled release

Controlled deliver and release molecules have a huge application such as pharmacology, cosmetic and drug delivery. However, precise release the molecules is difficult to realize. We in the lab apply microfluidic technology and generate picoliter-sized particles or capsules through single or double emulsions as the template. Interesting materials are encapsulated in the core, we control the release behavior by fine tuning the shell thickness, and its compositions. We also try to develop new materials that would be suitable for sensitive molecules encapsulation and release. For example, we encapsulate antibodies in a degradable PLGA shell that can be injected in the patient and finely release inside. We can also encapsulate small molecular or liquid metal for the detection of electronic property variations. Liyuan Zhang

Fabrication of Uniform Thickness Spherical Shells from Hydrodynamically Centralized Double Emulsions

Forming uniform thickness spherical shells is critical for providing better mechanical performance for core-shell structured microspheres. However, it still remains a significant challenge to precisely control the concentricity of core-shell materials. To solve this problem, a hydrodynamic method is investigated for centering cores in double emulsion droplets with sizes ranging from tens to hundreds of microns. The cores stay at the center of the droplets due to the hydrodynamic pressure generated in the liquid shells, despite the significant density difference between core and shell. Therefore, by using polymerizable shell material, which can be solidified thermally or by illumination, core-shell microspheres with gas, liquid or solid cores can be successfully produced with uniform thickness coatings using the present method. Shuaishuai (Shawn) Liang

Microfluidic Production of Triple Emulsions to Create Edible Microcapsules for Intestine-Targeted Delivery

Small intestine is the main organ for human digestion and absorption, many oral drugs or functional substances may undergo degradation, destruction or inactivation before they can reach small intestine, which leads to their low bioavailability, efficacy, or activity. Thus, we designed edible microcapsules from microfluidic triple emulsions to encapsulate and deliver these cargoes. These microcapsules have an inner water core to load cargoes, and double shells, an inner lipid-based shell and an outer protein-based hydrogel shell. The protein-based shells will be digested in stomach, then the lipid-based shell will be digested in small intestine. The thickness and composition of each shell can be carefully designed using a microfluidic device to control the digestion of these microcapsules during human gastrointestinal tract. These microcapsules will protect inner cargoes from the oral and gastric environment and finally release them in small intestine. These microcapsules may have potential applications for intestinal delivery of drugs, enzymes or probiotics. Xing Chen

Biomimetic alignment structures derived from microﬂuidic shearing

Natural material, such as sea urchin and spider silk, are well known for their excellent strength, modulus and toughness. Such properties are attributed to their ordered microstructures. Some fabrication strategies, including layer-by-layer blading, casting and vacuum filtration, have been used to develop alignment microstructures. Herein, based on the soft lithography, we design shear microfluidic channels to align rigid macromolecules, nanofibrils and nanosheets and try to construct hydrogels with alignment microstructures, which can be used in the areas of bioelectronics. Our previous experiments have demonstrated the shear microfluidic channels can promote the PEDOT-PSS alignment. Wei Gao and Zhouyue Lei

Bioinspired three-dimensional network hydrogel based on polysaccharides

Hydrogels are hydrophilic colloids with a three-dimensional network. Hydrogels can change their morphology under external stimulation, so they have broad application prospects in the fields of sustained-release drugs, flexible devices and sensors. Inspired by mussel chemistry, the dopamine oxidation self-polymerization reaction was used to solve the problem of instability of nanomaterials in solution. At the same time, we designed a variety of hydrogels based on polysaccharides and micro-nanomaterials, in which surface chemical / physical modification can be expanded the application of hydrogels in the field of biomedicine; the ordered network structure gives hydrogels the characteristics of slow release, self-healing properties and high strength. Lin Wang

Microfluidic synthesis of functional nanomaterials for artificial olfactory sensing

Microfluidics has attracted much attention due to its various features that enable us to access monodispersed micron-sized droplets. The extension of the microfluidic approach to controlled nanomaterial synthesis has also been expected and explored, while it is still challenging to rationally design a flow sequence for this purpose because the dimension of typical nanomaterials is a few orders of magnitude smaller than the dimension which is easily controlled with microfluidic techniques. We are trying to establish microfluidic synthesis for various nanomaterials by focusing on nucleation/growth control. As a variety of experimental parameters can be systematically tuned in microfluidic approaches, nanomaterials with different functionalities are available through this project. We have demonstrated that some of the nanomaterials that were successfully synthesized already were useful for olfactory sensing where a wide variety of functional materials are required to discriminate gaseous mixtures with extreme complexity. Kota Shiba

Continuous Preparation of Calcium Alginate Gel Fiber through Microfluidic Chip

Due to its low immunogenicity, calcium alginate gel fiber is a popular material in biomedical applications, especially tissue engineering. Microfluidic technique has been widely used for calcium alginate gel fiber preparation and allows to give it some new properties, simultaneously. However, in most conditions, a coagulation bath is required when preparing calcium alginate gel fiber. In fact, calcium alginate gel is elastic and has high rupture strength, which makes it possible to be collected from microfluidic chip directly. The challenging is how to solve the clogging problem of micro-channel once fiber forms. Here, a novel strategy for continuous preparation of calcium alginate gel fiber on chip is developed without coagulation bath. Dehydrated calcium alginate fiber achieves a high strength as 222.9 MPa. This work has great potential for making 3D structure gels for tissue engineering. Guangming LI

Controlled Assembly of Biocompatible Amphiphilic Polyphenol-Based Nanoparticles for Droplet Microfluidics as an Alternative to Copolymer Surfactants

The traditional fluorinated surfactant used in droplet microfluidics has the problems of complicated and costly synthesis conditions, cross-contamination of droplet contents, and lack of reactive functional groups, etc. To address these problems, my research focuses on developing an amphiphilic polyphenol-based nanoparticles to replace the traditional surfactants that can be used to create low-cost, stable, bio-compatible droplets for microfluidics-based digital PCR or other high-throughput screening applications. The polyphenol and collagen macromolecule with easily controllable charge properties are introduced to construct amphiphilic polymer-based nanoparticles for stabilizing the drops. This novel droplet surfactant can not only stop the leakage of small molecules in a droplet, and also provide a sufficiently rigid interface to enable the culture of adherent cells such as fibroblasts and breast cancer cells, which could enable new applications for high-fidelity biochemical assays. Gao Xiao

Microfluidic design of hierarchical semiconductors

Heavy dependence on fossil fuels has raised concerns regarding the sustainability and environmental impact of modern-day energy production, which has motivated an urgent need for renewable source of clean energy. Semiconductor-based photocatalysts have received increasing attention for solving both fossil fuel depletion and environmental pollution at the same time. Hierarchical structures, which have multimodal or multiscale porosity, are very favorable for light harvesting, electron and ion transport and thus endowing them with technological importance in photocatalysts design. Microfluidic approach, with advantages of precise control over particle shape and size, is an effective way to design a well-defined hierarchical structure. Therefore, we are trying to design hollow structured TiO₂ semiconductor by microfluidic synthesis. Moreover, this hollow structured TiO₂ semiconductor can be further optimized by the integration of other components (e.g. CdS, Carbon quantum dots) in a ternary composite system. Siming Wu