This PDF file contains the front matter associated with SPIE Proceedings Volume 10875 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Fused silica glass is the material of choice whenever high chemical and thermal resilience combined with high optical transparency is required. These properties make fused silica glass interesting in microfluidics for next generation chemical synthesis reactors as well as microoptics and photonics. However structuring of fused silica glass is difficult and upscaling of microfluidic concepts in glass from laboratory scale prototypes to mass market manufacturing remains a problem. Polymers on the other hand remain the material of choice for low cost, disposable components in mass market manufacturing. We want to close the gap between the superior material properties of fused silica and the ease of highthroughput polymer molding. Here we present high-throughput thermal replication of fused silica glass using thermal nanoimprinting and roll-to-roll replication. Therefore, thermoplastic nanocomposites are structured using classical polymer molding processes at moderate temperatures of 110°C and pressures of 27°MPa. Structuring can be done with submicron resolution and a surface roughness of a few nanometers. Roll-to-roll replication allows structuring these thermoplastic nanocomposites with speeds up to 5 m/min. The structured thermoplastic nanocomposites are then turned into fused silica glass in a final heat treatment.

We report the fabrication of pure proteinaceous high-aspect-ratio microstructures made by femtosecond (fs) laser multiphoton cross-linking for different variants of serum albumin, mouse serum albumin (MSA) and bovine serum albumin (BSA). Recently, use of laser direct writing to fabricate 3D microstructures made of protein has enabled applications towards cell culture and pH-actuation. This method employs the direct exposure of a focused fs laser into aqueous solution containing protein molecules enabling fabrication of solid protein structures by cross-linking protein molecules along the arbitrary exposure pathway. Preliminary high-aspect-ratio microstructures are examined by scanning electron microscopy. We report mechanical analysis of different structure concepts by finite element analysis to approach high-aspect-ratio design despite 1 MPa-Young’s modulus of protein hydrogel. Protein as a biomolecule and relevant material group for pharmaceutical developments is a promising choice for biomedical device fabrication. Fabrication of biomedical MEMS based on biomaterials such as protein might directly become important for implant and biomedical technologies. (154 of 200).

Microfluidic paper-based analytical devices (µPADs) have gained a lot of attention in recent years because they enable the production of diagnostic devices in a simple and cost-efficient way. To control the fluidic flow, hydrophobic barriers are generated that reach into the fibrous structure of the paper. Popular methods for creating such barriers are wax printing or polymer deposition. These barriers are however very stiff: bending or folding leads to the destruction of the barriers. Another problem is the low resistance of common barrier materials against different solvents, which makes it impossible to execute chemical tests on paper. Destruction of the barriers leads to leakage and causes assay failure. Here we present a method that produces bendable hydrophobic barriers on paper by photolithography. These barriers are based on silanes and withstand solvents such as DMSO. We show that these barriers can also be autoclaved, which is important for conducting biological assays using bacteria or cells on μPADs.

Microfluidic devices are broadly used in research, diagnostics, analytics and many more fields. Their eligibility to run with small amounts of sample are one driving force to expand their utilization into more applications. While glass is an ideal material for microfluidics, few technologies for the micromachining of glass are available. They are usually limited regarding precision and freedom of design, and introduce stress, cracks or other damage into the material. Additionally, they are restricted to certain glass types or do not meet the throughput requirements for mass production. In this work, we discuss - in the context of microfluidics - the recently developed Laser-Induced Deep Etching (LIDE) technology that has overcome the aforementioned issues. It is shown how a broad range of features such as high-aspect ratio through holes, cutouts, slits etc. are realized without introducing stress or other deficiencies. Furthermore, the LIDE technology is discussed in relation to accessory technologies such as glass-plastics and glass-glass joining, as well as selective metallization. These accessory technologies are critical for utilization in areas such as medical diagnostics, single cell studies, lab-on-a-chip applications and many more.

Here, we demonstrate the additive manufacturing of two key microvalve designs, namely Nordin’s and Quake’s microvalves, based on a formulation consisting of tri(propylene glycol) diacrylate (TPGDA) as a base material, diphenyl(2,4,6-trimethylbenzoyl) phosphine oxide (TPO) as a photoinitiator and Sudan1 as the UV-absorber via micro-stereolithography (μSL). Mechanical measurements of test prints show an average Young’s modulus of 15.7 MPa, which is eight times lower compared to several previous studies on 3D-printed microvalves and micropumps based on poly(ethylene glycol diacrylate) 255 (PEGDA-252). We use a high-resolution Cerafab7500 printer (Lithoz GmbH, Vienna) with a minimal lateral resolution of 10.3 μm to print membrane valves with voxel dimensions down to 60μm. Particularly, we study the effect of different comonomers added to the photopolymer formulation – neopentyl glycol propoxylate (1 PO/OH) diacrylate (NPGPDA), 1,6- hexanediol diacrylate (HDDA) and 2-phenoxyethyl acrylate (POEA) – on the layer thickness, which is identified to be a crucial parameter. 3D-printed valves are tested regarding maximum operating pressure withstanding pressures of up to 5 bar. We show that TPGDA-based resins combine high flexibility, mechanical stability, and sufficient resolution for the future design of flow control units in microfluidics.

Polydimethylsiloxane (PDMS) remains the polymer of choice for many microfluidic applications. Standard soft lithographic methods are based on channel molding and consecutive bonding of a lid. We have recently shown the production of smooth, circular three-dimensional channels by zero-gravity printing of surfactant liquid threads into PDMS matrices, a technique we term “Suspended Liquid Subtractive Lithography” (SLSL). A commercial cartesian 3D printer was used for the experiments but was shown to be not ideal due to the movement of the printer bed, which causes distortions in the soft SLSL structures. In this work, a new generation of printers was designed, based on a delta printer system. The printer was equipped with a precision syringe pump and a solenoid valve which prevents dripping of the surfactant off the needle. Printing parameters such as the printing speed and channel diameters were evaluated. It was found that channels be printed with high fidelity over high lengths of more than 80 cm.

Soft lithography provides a convenient technique for prototyping miniaturized fluidic systems. However, 3D-printing techniques offer shorter lead times and greater three-dimensional design freedom, as well as circumventing the manual alignment and inter-layer bonding challenges of soft lithography. As a result, attention has moved towards additive fabrication solutions. Fused deposition modelling (FDM), inkjet, and stereolithographic projection-based 3D-printing solutions have demonstrated the possibility of printing master molds as well as encapsulated fluidic networks directly. However, all of these techniques typically require the use of solid support structures when printing overhanging features as are required for encapsulated fluidic channels. This support material is time-consuming or, in some cases, entirely impractical to remove from small-scale, encapsulated channels. Additionally, most existing printing techniques are limited to materials that are orders of magnitude higher in elastic modulus than biological tissue. Finally, process-induced surface roughness makes microscopy challenging. In contrast, we have introduced a new additive technique, computed axial lithography (CAL), which enables volumetric 3D-printing by illuminating a rotating volume of photosensitive material with a 3D light intensity map constructed from the angular superposition of many 2D projections. The projections are computed via the exponential Radon transform followed by iterative optimization. Oxygen inhibition-induced thresholding of the materials’ dose response enhances patterning contrast. Here, we report the application of CAL to fabricate transparent 3D fluidic networks in highly compliant and resilient methacrylated gelatin hydrogels, as well as in stiffer acrylates. Uncured resin provides mechanical support during printing, so the need for solid support structures is eliminated.

The raising importance of stereolithography printers for rapid prototyping of microfluidic chips is due to the combination of affordable machinery and high resolution. However most commercial printing materials have low chemical resistance to solvents and strong acids. Perfluoropolyethers (PFPE) are a class of materials which show a high chemical resistance. Here we present a new resin formulation using PFPE methacrylates which allows 3D printing of microfluidic structures with a channel size of 200 μm and a transparency of 90% in the visible light region. We further show that using an adapted PFPE resin formulation superhydrophobic surfaces can be printed.

We developed a next-generation method for chemical in–situ combinatorial biomolecule array synthesis. This allows for an unprecedented combinatorial freedom in the automated chemical synthesis of molecule arrays with very high spot densities. Key feature of this new method is an automated positioning and laser transfer process: Small solid material spots are rapidly transferred from a donor film to an acceptor surface, requiring only minute amounts of materials. The transfer is performed with different and easy-to-produce donor slides. Each donor slide bears a thin polymer film, embedding one type of monomer. The coupling reaction occurs in a separate heating step, where the matrix becomes viscous and building blocks can diffuse within the material and couple to the acceptor surface. Since these transferred material spots are only several nanometers thin, this method allows for a consecutive multi-layer material deposition of e.g. activation reagents and amino acids. Subsequent heat-induced mixing facilitates an in–situ activation and coupling of the monomers. Positioning several of such resin spots, containing different chemical reagents, on top of each other, will enable for the first time in such small dimensions unique chemical synthesis strategies for each spot. Amount and concentration of the deposited materials can be adjusted with the laser parameters. Employing similar arrays, we can analyze the human immune response towards the proteome of different pathogens. We screened several peptide array replicas with different patient sera. The screenings resulted in significant hits in several proteins with interesting implications for future diagnostics and vaccine development.

The development of ultrafast X-ray free-electron laser (XFEL) sources and third-generation synchrotrons has opened many new horizons for the study of complex molecular structures and their reaction kinetics. An essential element of these types of experiment is the method used for sample delivery. Microfluidics technology provides the ideal platform for performing these types of measurements since it enables control, manipulation and delivery of small volumes of fluid inside microchannels. Several key functions including mixing, particle separation, and injection, can be integrated on a single chip making the technology very attractive for use in Xray characterisation of molecular dynamics. Key challenges however, in using microfluidics to both mix and deliver samples, include chemical inertness and mechanical stability of the devices, particularly at micron length scales. Here we report a repeatable method for fabricating microfluidic mixer-jet devices based on photolithography and SU8 with a glass substrate. In experiments we have shown that these devices can withstand the high gas pressures required to produce stable, long-range, liquid jets. Coupled with their chemical inertness and reproducibility this makes them promising candidates for time-resolved X-ray diffraction measurements of molecular dynamics. Incorporating an integrated serpentine micromixer capable of homogeneous mixing prior to the liquid jet the devices presented here can be applied to the study of the dynamics of chemically driven biomolecular reactions. The focus of the current work is on the experimental characterization of the mixer through analysis of the concentration profiles along the length of the serpentineshaped microchannel.

A confocal Raman microscopy technique has been designed and demonstrated that measures the temperature rise and profile in microfluidic devices. The system is based in the deformation of the water Raman peak assigned to the O-H stretching at 3400 cm⁻¹ that occurs with temperature keeping an isosbectic point at 3425 cm⁻¹ . Hence two photon counting detectors that sample the Raman emission at each side of the isosbectic point are used to monitor the water temperature. Using a confocal detection scheme the spatial resolution of a confocal microscope can be obtained to map the temperature profile within small microfluidic structure in a noninvasive manner. The differential signal between the two channels normalized by the added signals has a linear dependence with temperature that yields a sensitivity of 0.8 K using a 1s integration time and a count rate per channel of 1.5 · 10⁵ . The pump laser used had a 405 nm wavelength and 20 mW average power. The confocal collection was performed by a single mode optical fiber and the explored volume was of about 40 μm³ . The temperature rise in electrotrofluidic devices was studied showing that the temperature increase depended on the power used to move the sample along the channel (electroosmotic flow) and the particular design and structure of the device that determines the heat dissipation mechanism. The scheme proved useful to evaluate and prevent detrimental temperature effects with the advantage that no specific temperature sensitive particle needs to be added to the fluid, and has the additional virtue of allowing spatial scans in 3D.

Acoustophoresis devices are proposed as tools for manipulation and diagnostic in microfluidic environments. We demonstrate that their diffusion can be supported and enhanced by Digital Holography. Indeed, this technique covers all the current imaging needs and can stimulate the development of novel applications thanks to its unique features. The numerical refocusing is exploited to control the manipulation during acoustic focusing and acoustic-driven aggregation and to retrieve the 3D trajectories of tracer beads for the ultrasound field calibration. Besides tracking, DH displays its full potential when USs are used to directly manipulate or deform cells. In this case, numerical processing provides information on the sample movement and morphology, with potential applications in the field of diagnostic.

We have developed a rapid and novel technique for concentrating cells into 3D clusters which are then embedded in an agar hydrogel. This method supports cell growth and proliferation with a steady nutrient supply through the porous hydrogel. For tissue engineering studies, the creation of cell clusters within a controlled size range is necessary to perform precise biological experiments and measure functions. Our precisely controlled cell clusters can be reproducibly formed for different sizes between 0.1 mm to 5 mm in diameter, with cell numbers up to 10⁶ cells/cluster. The concentration of cells is achieved using a device we previously developed, that utilizes a combination of electrical and hydrodynamic phenomena. The results were obtained using an 80 μL drop containing HeLa cancer cells placed over an interdigitated electrode array. The electrohydrodynamic phenomena was produced using a sinusoidal voltage (10 V_pk-pk and 50 kHz). This voltage application creates Joule heating resulting in a buoyancy driven convective flow pattern directed towards the center of the droplet. In addition, the same interdigitated electrode structure also induces dielectrophoretic (DEP) levitation of the suspended cells which prevents cell settling and non-specific adhesion. The dense clustering of cells is achieved within 10 minutes of AC voltage application. Furthermore, using staining we have demonstrated that cell viability was measured as 90% after the formation of agar-embedded cell clusters and 80% over 72 hours.

Demand for low-cost alternatives to conventional medical diagnostic tools has been the driving force that has spurred significant developments in the diagnostics field. Lateral flow devices (LFDs) are one of the simplest and most established formats of paper-based devices, and are regarded as ideal point-of-care diagnostic solutions. In recent years, there has been an increasing need for performing multiplexed diagnostics at the point-of-care for rapid and simultaneous detection of different analytes within a single fluidic sample. Here, we report a novel multiplexing strategy – detection of different analytes individually in the multiple paths of a single LFD. These multi-path LFDs were created via the precise partitioning of the single flow-path of a standard LFD using our previously reported laser direct-write (LDW) technique. Unlike other multiplexing methods, our distinctive approach, presented here, creates multiple parallel flow-paths inside a ‘single’ LFD without increasing its original footprint, and hence does not require larger sample volumes, and, most importantly, eliminates the interference between individual detection sites positioned within the same channel as in the case of other multiplexing strategies. We show the use of an LDW-patterned dual-channel LFD as an example for the implementation of multiplexed detection of C-reactive protein (CRP) and Serum amyloid A-1 (SAA1), biomarkers commonly used for the diagnosis of bacterial infections. To further validate our multiplexing strategy, we have also tested our LFDs with clinical samples (blood serum from patients with increased systemic inflammation) and the results show a high consistency with those acquired using the gold-standard, an ELISA test.

In this paper, we describe the components of a portable point-of-analysis (PoA) platform prototype. This prototype is capable of simultaneously controlling the operation of integrated electrodes in the microchannels of a capillary-driven microfluidics device, which is used to manipulate microbeads flowing with the fluid, detection and analysis of the fluorescence signal emitted by the labeled proteins captured on the microbeads surface. The microfluidic chip employs integrated planar metallic electrodes inside the microchannels for creating a highly localized non-uniform electric field, capable of manipulating and immobilizing polystyrene microbeads of diameter from 1 μm to 10 μm in the flowing fluid, via dielectrophoresis. The analysis platform integrates several modules responsible for energizing and controlling the electrodes in the chip, generating and detecting the fluorescence signal, processing and transforming the captured data, communicating and providing access to cloud storage through the smartphone and securely handling the chip in a dark chamber. A mobile device application manages the platform operation via Bluetooth and connects to a Cloud service for further data storage and analysis. We demonstrate the operation of the analysis device by measuring the fluorescence emission of functionalized 3 μm microbeads trapped via dielectrophoresis above the integrated electrodes as they reach a trapping equilibrium state.

When a laser beam is focused into a volume of highly absorbing thermal medium, gas bubbles can be generated due to the temperature change caused by the laser. In our previous work, it has been shown that these optically generated microbubbles can be steered/manipulated using a low power focused laser beam. Also all possible forces acting on a microbubble which is confined inside a horizontal glass container have been studied and a model is developed to calculate the thermo-capillary force acting on the microbubble. It has been experimentally shown that the microbubble is attracted towards the laser beam due to the thermo-capillary force which is usually larger than the optical force. When developing the complete force model, the thermo-capillary force, optical force, buoyancy force and viscous force have been considered. In our latest work, 2D microbubble trapping is extended to 3D by considering both transversal and axial temperature gradients acting on the microbubble. Microbubbles are generated inside a thick cuvette containing a liquid with absorbing dye through nucleation. Both transversal and axial temperature profiles are calculated by separately solving transversal and axial heat equations and matching the peak temperature change. In this work, the thermo-capillary force on a microbubble is determined by directly solving the 3D heat equation by 3D Fourier transform methods.

Circulating tumor cell (CTC), entering into bloodstream from its originating tumor, is found to be responsible for cancer metastases and CTCs’ detection can serve as an important stage for cancer diagnosis. Deformation-based separation technique, which utilizes differences in deformability of the cells, has shown promising abilities in CTC detection and manipulation due to its simplicity, high performance and low cost. In this method, CTCs are trapped while more deformable blood cells (e.g. White Blood Cells) are able to squeeze through the filtration channel at the specified operating pressure. In this work, we employed numerical simulation to study the pressure-deformability behavior of a single cell passing through a cylindrical microfilter. An Adaptive-Mesh-Refinement (AMR) method is employed, which reduces the computational effort by concentrating more on the critical regions of the domain. The cell is modeled as a Newtonian liquid droplet and the effects of different design parameters such as operating flow rate and cell viscosity on pressure signature were studied. Then, the critical pressure for the CTC is analyzed as it plays an important role in device operation. We found that critical pressure is linearly related with the flow rate and the viscosity of the cell. Our study provides an insight into the cell squeezing process and its characteristics, which can be used for designing the nextgeneration deformation-based CTC microfilters.

While lab-on-a-chip systems have become more and more widely used in many fields in diagnostics, analytical and life sciences, most of the systems still have to be considered as stationary, typically desktop-sized instruments. While the actual microfluidic cartridge often is comparatively compact, the associated instrument to operate this cartridge remains large, limiting the use of such systems in applications outside of a laboratory environment. Two main aspects contribute to this situation: Detection systems, especially sensitive optical (e.g. fluorescence) detection systems remain relatively large. The fluidic control elements, especially when reagents have to be delivered from a reservoir in the instrument to the cartridge, also contribute to the system size and weight. We have tried to circumvent these problems by integrating both the detection system as well as all required liquid reagents into the disposable microfluidic cartridge. The technology used for the realization of the detection system is the multilayer inkjet-printing of organic semiconductor materials (PEDOT:PSS) in order to create light sources and photodetector elements directly on the cartridge. This printing technology can be seamlessly integrated into the manufacturing workflow of the cartridge fabrication. All liquid reagents (currently 6) for an exemplary immunoassay on this platform are integrated using blisters which can be easily actuated either manually or by a simple linear actuator. Data readout as well as system control are planned to be executed using a smartphone, thereby further reducing the complexity and size of the instrument.

Light irradiation is a promising way for spatial gel formation, and it is useful in cell arrangement by control of the shape of gels. To form the shape of gels by light irradiation, temperature control and irradiation of ultraviolet light, which causes damage to cells, are required. In this study, we propose a shape control method of DNA hydrogels by photodecomposition with visible light. By design of DNA sequences and modification of molecules, DNA hydrogels can be decomposed by changing the environment including temperature, pH, and the presence of specific molecules. In our method, the DNA hydrogels are constructed by self-assembly of Y-motif DNAs (Y-DNAs) combined with linker DNAs (L-DNAs). For optical control, the L-DNA is modified with quenchers. When quenchers are optically excited, thermal energy is released via a non-radiative relaxation process of the quenchers, and then denaturation of DNAs consisting of Y-DNAs and L-DNAs is induced. Separated Y-DNAs bind with a Cap-DNA which prevents Y-DNAs from recombination with L-DNAs, and DNA hydrogels are decomposed as a result of the separation of Y-DNAs and L-DNAs. This decomposition is only induced within the irradiation area. Thus, the shape is changed by control of light distribution. In experiments, we demonstrated the decomposition of DNA hydrogels according to holographically generated light patterns. This result shows that the shape of DNA hydrogels can be controlled by visible-light irradiation without changing the environment.

In this work, we report fast and efficient synthesis of ZnO-NWs in-situ within microfluidic chamber taking all the advantages of microfluidic devices. The growth done in dynamic mode involving flow of the growth solution inside the microchamber. Well-oriented ZnO-NWs are achieved in just 8-16 minutes in dynamic mode having similar properties to the synthesized NWs in 2-3 hours growth time using the static method. The morphology and optical properties of the ZnONWs characterized using SEM and UV-Vis spectroscopy. This method opens the door for fast, cheap and localized growth of NWs to be used within microfluidics platforms.

We report the use of a laser-based direct-write (LDW) technique that allows the fabrication of porous barriers, which enable in-line filtration within a paper-based microfluidic device. The barriers were produced within porous substrates, namely nitrocellulose membranes, via local deposition of a photo-polymer that was subsequently polymerised by exposure from a laser source. Adjustment of the photo-polymer deposition parameters determines the porosity of the barriers, which, when carefully designed and integrated within a fluidic channel, can act as filters that enable either complete blocking, selective flow or controlled separation of particles of different sizes within a fluid travelling through the channel. We have successfully identified the fabrication parameters for the creation of barriers that allow the filtration of two different types of particles, Au-nanoparticles with sizes of 40, 100 and 200 nm and latex microbeads with sizes of 200 nm and 1 μm, dispersed within an aqueous solution. We also report the use of a variable-porosity barrier for selective separation of latex microbeads from Aunanoparticles, thereby showing the usefulness of this technique for enabling in-line filtration in such paper-based microfluidic devices.

The technology of 3D bioprinting has gained significant interest in biomedical engineering, regenerative medicine, and the pharmaceutical industry. Providing a new scope in tissue and organ printing, 3D bioprinters are becoming commercialized for biological processes. However, the current technology is costly, ranging from USD$9,000-$30,000 and is limited to customized extrusion methods. Multiple microfluidic pump systems for bioink extrusion are commercially available at USD$30,000. Additionally, the use of Cartesian systems for 3D printing restricts the user to three axes of movement and makes multi-material modeling a challenge. Consequently, it was proposed to design a cost effective robotic 3D bioprinting system, compatible with peptide bioinks which were developed at KAUST Laboratory for Nanomedicine. The components of the system included a programmable robotic arm, an extruder for bioprinting, and multiple microfluidic pumps. The extruder was designed using a coaxial nozzle made of three inlets and one outlet. The programmable microfluidic pumps transported the peptide bioink, phosphate buffer saline (PBS) and human skin fibroblast cells (in cell culture media solution) through the nozzle to extrude a peptide nanogel thread. Model cell structures were printed and monitored for a period of two weeks and subsequently found to be alive and healthy. The system was kept well under a budget of USD$3,500. Future modifications of the current system will include adding a custom bioprinting arm to allow multi-material printing which can fully integrate and synchronize between the pumps and the robotic arm. This system will allow the production of a more advanced robotic arm-based 3D bioprinting system in the future.

The microfluidic probe (MFP) is a non-contact technology that applies the concept of hydrodynamic flow confinement within a small gap to eliminate the need for closed conduits, and thus overcomes the conventional microfluidic “closed system” limitations. It is an open-space microfluidic concept, where the fluidic delivery mechanism is physically decoupled from the target surface to be processed such as tissue slices or cell culture in Petri dishes. Typically, MFPs are manufactured using complex photolithography-based microfabrication procedures that limits innovation in MFPs’ design and integration. Recently, we showed that 3D printing can be utilized for rapid microfabrication of MFPs, where MFPs can be manufactured with built-in components such as reservoirs, fluidic connectors, and interfaces to the XYZ probe holder. 3D printing brings flexibility in MFP design, where different configurations and aperture arrangements can be considered. Currently, we are developing advanced MFPs that are integrated with other technologies and targeting applications in dielectrophoretic-based cell separation, immuno-based cell capture for isolating circulating tumor cells from blood samples, and efficient and selective single cell electroporation. In this invited paper, we highlight several MFP technologies we are developing.

Transport of chemotherapeutic drugs through tissues happens by convection and diffusion. In a normal healthy tissue, capillary vessels are highly pressurized when compared to the tissue interstitial pressure. Therefore, nutrients and drug molecules move from blood vessels to the healthy cells with the aid of capillary pressure. In the case of cancerous tissue, accelerated cell growth within normal cells in addition to disorganized blood vessel network limits the transport of nutrients and drug molecules to mainly diffusion. This happens due to the combination of high tumor interstitial fluid pressure and extracellular matrix (ECM) stiffening, resulting in a decrease of efficacy of delivery of drugs. This work investigated the use of hydrogel in order to mimic the tumor microenvironment in a microfluidic system. A hydrogel matrix was injected inside of a microfluidic device in order to mimic the extracellular matrix of a cancerous tissue. In addition, this work evaluated the transport of gold nanoparticles inside the microfluidic system, by tracking fluorescence.

A predominant challenge in tissue engineering is the need of a robust technique for producing structures with precise three-dimensional control of mechanical properties. In an effort to understand how to control the mechanical and chemical properties of materials patterned using stereolithography, this study focuses on the development of a model that allows for orthogonally programmable elastic modulus and geometry in a 3D hydrogel structure. In this study, we use pediatric physeal tissue engineering as a model application. Pediatric physeal injuries can be detrimental to children because damaged cartilage within the physis can lead to assymetric growth arrest. A challenge related to physeal tissue regeneration is the presence of three distinct zones within the physis or growth plate, where cells evolve differently and are known to be sensitive to the mechanical environment. We use a poly(ethylene glycol) diacrylate based photopolymerization chain-growth reaction with a modulus that can range from 600KPa to 39 MPa to spatially control the mechanical properties in our 3D parts and match the growth plate tissue environment. We apply Fourier transform infrared spectroscopy (FTIR) to quantify the degree of monomer conversion over time and intensity, while comparing it with a mechanical model that relates conversion to modulus. To evaluate the spatially controlled mechanical properties in printed structures, nanoindentation is performed to extract the modulus in each biomimetic zone. In this work we present the implementation of both a gradual change in mechanical properties, as well as a step function in 3D scaffolds on the order of 100 microns. This work enables predictive models of structural properties that can be translated into tissue engineering microstructures that match the native biomechanical environment of any tissue.

In global healthcare and point-of-care diagnostics there is an increasing request of medical equipment with devices able to provide fast and reliable testing for clinical diagnosis. In developing countries that lack of adequate facilities, this need is even more urgent. Lab-on-a-Chip devices have undergone a great growth during the last decade, supported by optical imaging techniques more and more refined. Here we present recent progresses in developing imaging tools based on holographic microscopy that can be very useful when applied into bio-microfluidics. Digital Holography (DH) is label-free, non-invasive, potentially high-throughput and, above all, quantitative. We show the recent advancements of DH in transmission microscopy mode, when this is applied to microfluidics to yield 3D imaging capabilities. Holographic flow cytometry through quantitative phase imaging and in-flow tomography for the analysis and manipulation of micro-particles and cells will be shown [1-3]. Medical diagnostic applications based on DH will be also shown. Moreover, we present a portable common-path holographic microscope embedded onboard a microfluidic device that paves the way to the application of DH on the field [4].

Here, a method to eliminate the trade-off between quality factor (Q-factor) and sensitivity of a one dimensional slot mode photonic crystal nanobeam cavity biosensor is presented. Applied method utilizes an optomechanical feedback mechanism in order to generate transverse gradient optical forces inside the cavity. A pump mode is utilized in order to generate the optical force, triggered by intrusion of analyte into the background medium. The amount of generated force is controlled via an interference mechanism at the output realized by the feedback loop. By utilizing created optical force, slot width of the nanobeam cavity is dynamically tuned and the quality factor degradation due to the decrease in the refractive index contrast of the cavity is compensated by enhancing the field confinement inside the cavity. With the contribution of the slot width tuning to the resonant wavelength shift, sensitivity of the biosensor is increased without any degradation of the Q-factor. Numerical analyses regarding the cavity design and the elimination of trade-off are provided. Obtained results show that the both performance can be increased at the same time.

In this work, a ring resonator is designed and analyzed for the spectral properties. A ring and a bus waveguide is designed with a core width of 0.2μm and cladding width of 2μm respectively. The bus waveguide is designed with a height of 14.4μ, width of 2μm and a layer thickness of 900nm is considered. The structure is simulated with a wavelength of 1.55μm. The core refractive index of 2.5 and the cladding refractive index of 1.5 is considered in the design. The separation between the ring and bus waveguide considered in the design is 0.72μm. A perfect electric conductor is considered at the boundaries of the ring and the bus waveguide. The meshing of the structure is done, which involves the finite element method (FEM). The power at the input port is given as 1W. The coupling of the light in the core of the bus and ring waveguide is observed. Which will give a better limit of detection, and is required for biosensor. An increase in the transmittance is observed by reducing the radius of the ring, various ring circumference is considered for the analysis. A small ring structure is taken for consideration, as the smaller ring will be useful in the bio-sensing application, which can further be fabricated for a point of care devices.

Over the last decade, there has been widespread consumer adoption of Internet of Things (IoT) devices for selfmonitoring of health and fitness. Wearable devices for instance now allow the general public to gather biometric and health-related data such as activity levels, sleep patterns, and heart rate metrics. These devices and the continuous data they generate are revolutionizing how people think about some of these metrics. Eventually, people will come to expect readily available information that can only be gathered by sampling biological samples such as sweat, saliva, blood or urine. As an example, the market has already seen the emergence of DNA ancestry tests and microbiome tests. However, a barrier to larger adoption of biomarker testing relates to ease of use; the collection of these biological samples is often a complex multi-step operation. Traditionally the field of microfluidics is regarded as the perfect tool to enable sensor miniaturization and small volume fluid handling for complex multi-step operations in point of care or clinical environments. Microfluidics is therefore well positioned to contribute to the development of new technologies for these exploding new markets. For direct to consumers applications, however, microfluidics will play a significant role in creating simple user experiences for sample collection and accurate biomarker testing. This review highlights trends and provides a technology development framework for those interested in developing microfluidics for consumer electronics for health applications.

Integrated-optical biosensors such as, for example, the microring resonator (MRR) and Mach-Zehnder interferometer, are more and more commercialized, mainly because of their high intrinsic sensitivity in combination with the possibilities they offer for integration in optofluidic devices. Previously, we have described the development and basic characteristics of MRR sensor chips that were fabricated in the TriPleX based silicon-nitride platform1 . In the present work, results are shown for the quantitative and sensitive detection of thrombin with aptamer-modified sensor chips. First, the modified MRR biosensor chips were tested for the binding and detection of thrombin using a repetitive number of binding/regeneration cycles on buffer sample containing 100 nM of thrombin. Then the binding curve was determined using different concentrations of thrombin, which revealed a limit of detection of 1 nM and a dynamic range up to roughly 0.5 μM of thrombin. Results from the thrombin binding experiment showed a stable performance during the course of multiple binding and regeneration cycles.

Fast liquid jets (<150 m/s) are used as a needle-free fluid injection into elastomeric tissue such as skin. Because the fluid droplets are smaller than a typical needle diameter, there is less collateral damage caused by the jets in the intervened body. In this study, we aim to investigate the potential of the method to deliver liquids into biological tissues with higher stiffness than skin. To address this challenge we have implemented an optofluidic jetting system capable of generating supersonic liquid microjets driven by laser cavitation. Considering microfluidic properties of the system, we have exceeded a method to produce jets in a repetitive regime with rates of up to 6 Hz, diameters of 10, 15 and 30 µm and velocities exceeding 550 m/s. We have characterized the injection depth with respect to jet speed, jet diameter and elastic modulus of the sample material. Experiments were performed on hydrogels with Young’s modulus from 8 kPa to 1 MPa, which covers the wide spectrum of biological elastomers like inner body organ tissues, blood vessels, skin or cartilage.

In ovarian cancer patients, the build up of fluid in the peritoneal cavity leads to the production of protein and cell rich asciites. Physiological movement establishes ascitic currents in the peritoneal cavity. The ascitic currents represent external flow which plays an important role in disseminating and modulating the biology of the ovarian cancer. Furthermore, the interstitial flow build-up inside tumor nodules establishes outward fluidic streams. The fluidic internal and external streams play an important role in drug delivery, which is also affected by permeability, an important physical property of the tumor. Permeability defines the flow dynamics over and through the tumor nodule, influencing therapy. The permeability of the tumor also affects the magnitude and distribution of fluidic shear stress experienced by the nodule. We propose to use experimental optical observations and mathematical descriptions of flow and mass transport for estimation of (i) the flow pattern around and through 3D porous cancer nodule surrogate, and (ii) the surrogate permeability. The permeability is estimated using an optimization technique in which the permeability value is iteratively modified to minimize the difference between the numerical solution of the mathematical model and the optical measurements. This algorithm is robust to discrepancy between the mathematical model and the experimental measurements. In this presentation, we show the feasibility of using particle image velocimetry (PIV) and confocal microscopy for estimating the permeability of a tumor surrogate by the optimization technique. Results suggest that the developed optimization toolbox can be used to estimate the tumor permeability in live 3D models of ovarian cancer.

This invited talk will present an overview of my team's research in integrated photonics and automated, integrated microfluidics for various applications in biosensing. This will include our previous work in collaboration with Prof Laura Lechuga on automated sensing of antibiotics in sea water, more recent work in collaboration with Prof Hatice Altug on sustaining and monitoring the signalling of single cells and our most recent work on point of care diagnosis of cardio biomarkers for the rapid and conclusive assessment of heart attack.

Droplet based microfluidic technology is a miniaturized platform for microbial analysis on picoliter scale. With its costefficiency, high-throughput and feasibility of complex handling protocols, droplet microfluidics is a favorable platform for applications such as microorganism screening or synthetic biology. Scattered-light-based microbial detection, in comparison to the widely used fluorescent-label-based approach, provides a contact-free and label-free, yet sensitive measuring solution. The angular dependency of scattered light delivers an elaborate information about the morphology and the physical properties, e.g. size and refractive index, of microbial samples. Due to the complexity and ambiguity of the droplet contents, an angle resolved scattered light detection system could provide powerful method for a label-free identification and quantification of the microbes in droplets. In this paper, a novel approach of light scattering measurement in Polydimethylsiloxane (PDMS) microfluidic chips is presented, engaging optical fibers for a light-scattering-based on-chip microbial detection. Optical fibers, with their fast readout and compact size, are very suitable for easier system integration towards flexible and versatile lab-on-a-chip applications.

Nowadays, high-speed video microscopy is used in many applications like microrheology^{1, 2} or flow cytometry³ to measure mechanical properties of cells or to identify their type. Typically, high-speed cameras use buffering to reach very high frame rates due to the limited bandwidth of the interface to a PC like Ethernet or USB. Additionally, analysis of large data is compute-intense and in many cases difficult to do online. We developed a system that consists of a high speed CMOS image sensor combined with a field programmable gate array (FPGA) and a pulsed LED illumination system. Due to an image transformation that is done on the FPGA, the dimensionality of the data is reduced without loss of important information. This leads to a significant reduction of the amount of data as well as to noise reduction as a side effect. Furthermore, we developed a modular analysis toolkit that can be used to do the whole analysis directly on the same FPGA online so that buffering is not required and measurements can run continuously on high frame rates. Hence, we can analyze a large total number of objects at very high throughput rates in microfluidic devices. We present the analysis of diluted whole blood in a microfluidic system with our device as well as a sorting application that uses multiple regions of interest that are observed simultaneously so that particles can be analyzed before and after a manipulation or gate.

C. elegans is an attractive model organism in biology, as it shows genetic similarity with humans, facilitates microscopic observation due to its transparency, and has a short life cycle. Moreover, many mutants expressing fluorescent proteins in particular cell types exist, and these can be advantageously used for gene/protein expression studies. Nematodes are traditionally cultured on agar plates seeded with E. coli bacteria as food and well plate-based worm cultures using liquid media have enabled high-throughput drug screening. In addition to the well plate format, microfluidics promises precise spatio-temporal handling and dosing of biological reagents for more controlled manipulation and culture of worms and embryos on-chip. I will first discuss reversible worm immobilization protocols, like the use of mechanical clamping or the temperature-sensitive sol-gel transition of a Pluronic solution, for high-resolution on-chip imaging. In particular, we exploited the imaging potential offered by microfluidic chips for performing fluorescent protein aggregation studies to characterize progress of neurodegenerative disease and for mitochondrial morphology studies. We have also implemented worm bio-communication assays on-chip, and have proposed microfluidic chips for automated embryo arraying, phenotyping, and long-term live imaging, as well as for drug studies performed during early embryogenesis. Microfluidic chips thereby allowed studying worm populations at individual animal resolution level and permitted investigating multiple phenotypes at different time points during worm development. Thereby we could observe individualized multi-phenotypic responses to drugs and genetic cues.

Antimicrobial resistance (AMR) has been identified by the World Health Organisation as a global threat that currently claims at least 50,000 lives each year across Europe and the US, with many hundreds of thousands more dying in other areas of the world. The current routine empirical antibiotic therapy protocols that involve laboratory-based bacterial culture testing normally takes up to 2-3 days and are a primary contributor to the global prevalence of AMR. There is therefore an urgent need for low-cost but reliable point-of-care diagnostic solutions for rapid and early screening of infections especially in developing countries that have a lack of both infrastructure and trained personnel. The objective of our research is to fabricate a novel paper-based bacterial culture device that can be used for infection testing even by unskilled users in low resource settings. Here, we present our preliminary results relating to use of our unique laser-patterned paper-based devices for detection and susceptibility testing of E.Coli/Psedomonas, one of the leading causes of urinary tract and upper respiratory tract infections. These paper devices were fabricated via a laser direct-write procedure that uses c.w. laser light at 405nm to cure a photopolymer and produce within paper substrates hydrophobic walls that extend through the thickness of the paper thereby defining separate test zones within the fluidic device. Our laser-patterned paper device has multiple test zones impregnated with agar (containing different antibiotics in various doses) allowing only the selective growth/inhibition and thus detection/susceptibility-testing of E.coli/Pseudomonas via a simple visually observable colour change.

Solid phase extraction (SPE) is widely used for pre-concentration of the target molecules in the liquid sample to realize a lower detection limit of the target molecules. Fluorescent detection often follows the SPE process to determine the existence and concentration of these molecules. However, conventional SPE process are complex and time consuming. We present a novel centrifugal microfluidic platform based on 3D printing technology in this paper. Specially designed mechanical pinch valves, which were controlled by the rotation frequency of the platform, were used to manipulate the flow of the reagent and fluid sample. The prototype of the proposed system was fabricated with in 3D printing technology. The platform was tested with 10ppm (part per million) standard oil-water mixing sample. Different stationary sorbent, such as C18, activated charcoal, and 3D printable porous polymer, were used and compared. The experimental results showed that the fluorescence intensity of the sample was significantly increased. This SPE platform is easy to operate and can be potentially used as a portable on-situ spilled oil enrichment and detection device. Other than crude oil, this platform can be also used for other pollutant in environment water.

Effective capture of cancer cells from whole peripheral blood samples, i.e. circulating tumor cells (CTCs), is still an existing limitation for liquid biopsy-based diagnostics. The well-established closed-channel herringbone micro-mixers are one of the widely adopted methods for isolating CTCs based on antigen-antibody interaction. However, they are known to be associated with several drawbacks, such as limited capture areas within the channels, restricted access to isolated cells, difficulties to achieve multiplexed antibody capture assays for immuno-phenotyping, and limited postprocessing possibilities. To tackle these issues, we developed a novel microfluidic probe (MFP) that is integrated with herringbone micro-mixers on its tip surface (HMFP). The tip surface was designed with 2-slitted apertures, one for injecting the cell suspension and the other for performing high flow rate aspiration to confine the flow. The herringbone mixing elements were distributed in-between the apertures for micro-mixing that enhances the CTCs capture on the antibodies-coated bottom glass surface. Unlike the closed herringbone chips, the functionalized bottom glass surface was kept large given the capacity for the MFP to work in scanning mode, and so it prevented cell capture saturation effect. Our MFP design and experimental setup showed a cell capture efficiency of 59-81% with flow rates of 0.6-2.4 mL/h. The capture of CTCs in an open microfluidic system allows for easy post-process and CTC analysis, such as single cell drug testing and mechano-phenotyping using atomic force microscopy.

This work presents the development of a micro-electro-fluidic probe (MeFP) platform as an affordable and flexible microfluidic tool for the transfection of single cells via electroporation. The platform constitutes of a 3D printed MeFP -- gold-coated microfluidic probe (MFP) with an array of pin shaped microelectrodes integrated on its tip -- and an ITO coated cell culture substrate. This setup, and submicron feature size of the MeFP, allows for a selective exposure of the targeted cell to both the electric field and hydrodynamic flow confinement (HFC) of an intercalating agent, to demonstrate transmembrane molecule delivery through electroporation. Results show successful transfer of propidium iodide (PI) through the membranes of single HeLa cells with an applied DC rectangular pulse– a proof-of-concept for MeFP’s application in delivering nucleic acids into eukaryotic cells (transfection). By adjusting the size of the HFC (varying injection and aspiration flow ratio), we show that the cell target area can be dynamically increased from the single cell footprint, to cover multiple cells. Finite Element model show that even with such low applied voltages (0.5- 3V_pk-pk), the electric field generated reach the reversible electroporation threshold. These results demonstrate the MeFP as an advancement to the currently available transfection technologies for gene therapy; delivery of DNA vaccines, in vitro fertilization, cancer treatment, regenerative medicine, and induced pluripotent stem (iPS) cells.