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U. Staufer

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3 records found

Submicron patterns-on-a-chip

Fabrication of a microfluidic device incorporating 3D printed surface ornaments

Journal article - M. Nouri Goushki, Abhishek Sharma, L. Sasso, Shuang Zhang, B.C.J. van der Eerden, U. Staufer, E.L. Fratila-Apachitei, A.A. Zadpoor

Manufacturing high throughput in vitro models resembling the tissue microenvironment is highly demanded for studying bone regeneration. Tissues such as bone have complex multiscale architectures inside which cells reside. To this end, engineering a microfluidic platform incorpora ...

Bone cell response to additively manufactured 3D micro-architectures with controlled Poisson's ratio

Auxetic vs. non-auxetic meta-biomaterials

Journal article - E. Yarali, M. Klimopoulou, M.K. David, P. Boukany, U. Staufer, E.L. Fratila-Apachitei, A.A. Zadpoor, A. Accardo, Mohammad J. Mirzaali

The Poisson's ratio and elastic modulus are two parameters determining the elastic behavior of biomaterials. While the effects of elastic modulus on the cell response is widely studied, very little is known regarding the effects of the Poisson's ratio. The micro-architecture of meta-biomaterials determines not only the Poisson's ratio but also several other parameters that also influence cell response, such as porosity, pore size, and effective elastic modulus. It is, therefore, very challenging to isolate the effects of the Poisson's ratio from those of other micro-architectural parameters. Here, we computationally design meta-biomaterials with controlled Poisson's ratios, ranging between -0.74 and +0.74, while maintaining consistent porosity, pore size, and effective elastic modulus. The 3D meta-biomaterials were additively manufactured at the micro-scale using two-photon polymerization (2PP), and were mechanically evaluated at the meso‑scale. The response of murine preosteoblasts to these meta-biomaterials was then studied using in vitro cell culture models. Meta-biomaterials with positive Poisson's ratios resulted in higher metabolic activity than those with negative values. The cells could attach and infiltrate all meta-biomaterials from the bottom to the top, fully covering the scaffolds after 17 days of culture. Interestingly, the meta-biomaterials exhibited different cell-induced deformations (e.g., shrinkage or local bending) as observed via scanning electron microscopy. The outcomes of osteogenic differentiation (i.e., Runx2 immunofluorescent staining) and matrix mineralization (i.e., Alizarin red staining) assays indicated the significant potential impact of these meta-biomaterials in the field of bone tissue engineering, paving the way for the development of advanced bone meta-implants. Statement of significance: We studied the influence of Poisson's ratio on bone cell response in meta-biomaterials. While elastic modulus effects are well-studied, the impact of Poisson's ratio, especially negative values found in architected biomaterials, remains largely unexplored. The complexity arises from intertwined micro-architectural parameters, such as porosity and elastic modulus, making it challenging to isolate the Poisson's ratio. To overcome this limitation, this study employed rational computational design to create meta-biomaterials with controlled Poisson's ratios, alongside consistent effective elastic modulus, porosity, and pore size. The study reveals that two-photon polymerized 3D meta-biomaterials with positive Poisson's ratios displayed higher metabolic activity, while all the developed meta-biomaterials supported osteogenic differentiation of preosteoblasts as well as matrix mineralization. The outcomes pave the way for the development of advanced 3D bone tissue models and meta-implants.@en

Bone cell response to additively manufactured 3D micro-architectures with controlled Poisson's ratio

Auxetic vs. non-auxetic meta-biomaterials

Journal article - E. Yarali, M. Klimopoulou, M.K. David, P. Boukany, U. Staufer, E.L. Fratila-Apachitei, A.A. Zadpoor, A. Accardo, Mohammad J. Mirzaali

Contributed

17 records found

Design of a miniature gas exchanger for oxygen control in microfluids

Design, integration, fabrication and validation of a miniature cell medium gas exchanger to control (sub)physiological oxygen concentrations on a liver chip

Master thesis - M.P. van Reeuwijk, U. Staufer, Matthijs Langelaar, N.J.H. Raat

Current technology of Organ-on-Chips allows investigation of human cells outside the body including a microfluidic medium flow. Control of oxygen in this microfluidic flow is required to mimic the situation as in the human liver (physiological) or to create temporary low oxygen c ...

Design of a membrane for a lung-on-a-chip device

Design and testing of a membrane concept incorporating a dynamic pore size to study the alveolar-capillary barrier in vitro

Master thesis - S.A.M. den Boer, U. Staufer, Massimo Mastrangeli, Robbert Rottier, P. Boukany, E.L. Fratila-Apachitei, C.M. Boutry

In vitro models are fundamental in the study of cell behaviour, the physiological function of organs, and their response to drugs and toxins. However, the shortage of accurate and reliable in vitro models calls for the development of in vitro lung models that better recapitulate ...

Direct or Indirect?

Unraveling the bandgap nature of metal halide perovskites

Master thesis - M.M. Ackermans, U. Staufer, Bruno Ehrler, Eline M. Hutter, P.G. Steeneken, T.J. Savenije

Since the discovery of the photovoltaic properties of metal halide perovskites in 2009, the material has rapidly gained interest in the scientific community. In less than 10 years, the power conversion efficiency of perovskite solar cells (PSC) has increased from 3.9% to over 25% ...

Lung-on-a-chip

Design and Manufacture of a Resealable Device for Recreating the Alveolar-Capillary Barrier In Vitro

Master thesis - Z. Zabreen Nissar, U. Staufer

In vitro models are used for studying the physiological function of an organ, disease modelling and drug testing. Over the last decade, since their first commercial introduction, organ-on-a-chip (OOC) technology has proved to be able to recreate aspects of organ function that con ...

Silicon dioxide photonic mems

Chip-to-chip alignment with positionable waveguides

Doctoral thesis - T.J. Peters

THIS thesis describes the development of a positionable waveguide array realized in a silicon nitride / silicon dioxide (Si3N4 core / SiO2 cladding) photonic platform. The positionable waveguide array is the heart of a novel alignment approach for high precision multi-channel chi ...

Lung-on-a-Chip

Clamping Mechanism for a Resealable Microfluidic Device

Master thesis - A. Singh, U. Staufer

Lung-on-Chip (LoC) are devices that give cells a habitat in vitro that tries to more nearly imitate their natural environment in vivo. This microscale bio-mimetic device is designed to replicate essential features of the human lung within a controlled environment. While advanceme ...

Lung-on-a-Chip

Clamping Mechanism for a Resealable Microfluidic Device

Master thesis - A. Singh, U. Staufer

Tuning dynamics and dissipation dilution in 2D material resonators by MEMS-induced tension

Master thesis - M.P.F. Wopereis, P.G. Steeneken, G.J. Verbiest, F. Alijani, U. Staufer, S. Vollebregt

Nanomechanical resonators made of two-dimensional (2D) materials are the subject of intensive research due to their remarkable properties, allowing them to operate at high frequencies with high sensitivity. However, dissipation losses and manufacturing issues have prevented them ...

Fabrication of a microfluidic device by using two-photon lithography on a positive photoresist

Master thesis - G. van der Velden, U. Staufer

Organ-on-chip (OoC) devices are increasingly used for biomedical research and to speed up the process of bringing a medicinal drug from the lab to the market. The technology also addresses ethical issues linked to animal testing as it offers a reduction in animal experiments through its possibility to mimic the environment in the human body. Hence, it produces more relevant results than plain cell-culture experiments, while still sharing the possibility of high-throughput testing by simultaneously operating many devices in parallel. The main components of an OoC device are microfluidic channels and porous membranes. Current chips are often assembled from several parts. In the development phase a small change in design will cause a delay in the research because a new prototype has to be built again step-by-step. This research addresses this problem by targeting the fabrication of a microfluidic device in a single lithography and development step. A device consisting of two crossed channels at different heights separated by a membrane was chosen. The manufacturing method used was two-photon lithography (TPL) on positive photoresist AZ 4562. TPL exploits the fact that two-photon absorption non-linearly depends on the light intensity. The required intensity is only achieved in a small volume around the focal point, called the voxel. By positioning and moving this voxel inside the resist, 3D manufacturing is possible. Therefore the technique can be used for the single step fabrication of a closed channel. By vertically moving the voxel through the resist, pores can be manufactured. In literature an ellipsoidal voxel shape is assumed, leading to the assumption that the maximum voxel, and therefore pore diameter is found at the focal plane, i.e. at z = 0. However, this research shows that the voxel may also have an hourglass-shape for a high enough laser intensity. In this case the maximum voxel diameter is found at a distance z from the focal plane. For the production of pores, therefore the maximum voxel diameter instead of the diameter at the focal plane has to be taken into account. The smallest pores produced measured 250 nm - 290 nm. AZ 4562 was used as a stamp and a mold for the manufacturing of 3D topographical features on a PDMS surface. Finally the microfluidic device was successfully produced in a layer of 50 µm thick resist. The channel width was 100 µm and the height was 10 µm. The channels were separated by 10 µm in height. The sizes of the input and output holes were adapted to the diameter of the smallest available blunt needle, which is 210 µm.

Hamaker constant and tip radius determination in dynamic atomic force microscopy

Master thesis - M.P. James, F. Alijani, G.J. Verbiest, U. Staufer, P. Belardinelli, A. Chandrashekar

Dynamic Atomic Force Microscopy (dAFM) is an extremely powerful tool for exploring surface topology and nanoscale manipulation and characterization. A feature of dAFM is the existence of highly nonlinear forces between a cantilever tip and sample. One of these forces that plays a ...

Low-cost Benchtop Equipment and Procedures for Organ-on-Chip Prototyping

Master thesis - S.P. Aalbers, U. Staufer, Luigi Sasso, A.G. Denkova, A. Hunt

The Organ on Chip (OoC) market is fast-growing and has the promise to drastically reduce the cost of developing drugs and the need for animal testing. However, the growth could be obstructed by the difficulties of scaling up production of developed prototypes. Most OoC prototypes ...

Polymer nano manufacturing of a biomimicking surface used for kidney stone crystallization studies

Master thesis - R.M.B. Pleeging, U. Staufer, L. Sasso, D. Fan, H.B. Eral, G.J. Verbiest

Kidney stone disease is an increasing worldwide issue. There is a current lack of understanding of the exact mechanisms involved, partially due to the need for experimental instrumentation able to mimic the microenvironmental conditions present in vivo. As crystal nucleation often initiates at liquid-solid interfaces, the interface morphology plays a significant role in the rate of nucleation. Within the nephron, the functional unit of the kidney, four distinct segments can be distinguished that contain different surface morphologies. Particularly, the cells lining these segments contain protrusions in the shape of nanopillars that vary in length, diameter and spacing. Exploiting the opportunities provided by organ-on-chip technology, we designed and manufactured a microfluidic device proposed to increase our understanding of the exact mechanisms that drive kidney stone crystallization. We used two-photon polymerization to fabricate surfaces that contain these morphologies in materials possessing a Young’s modulus matching the value of the biological structures. After optimizing design and process parameters like laser power and scanning speed, we manufactured nanopillars with diameters in the range of 150-250 nm and aspect ratios up to 100 with which we can mimic the protrusions in the nephron. Pillar arrays were printed on a glass slide, and assembled with a polydimethylsiloxane (PDMS) microfluidic component (channels 150 um wide). We used high-resolution 3D printing to create master molds used for PDMS soft-lithography. After precise alignment, the two components were brought together and clamped mechanically with a 3D printed holder to ensure a watertight seal between the glass and PDMS. This microfluidic device was used to study crystallization of the most common type of kidney stone, calcium oxalate monohydrate (COM). Because of the chip dimensions combined with a surface morphology this device closely resembles a human nephron.

Tip identification in atomic force microscopy using nonlinear dynamics

Master thesis - T.W. Gribnau, E. Rull Trinidad, F. Alijani, U. Staufer, P.G. Steeneken, J.W. Spronck

Since its invention, the Atomic Force Microscope has emerged into one of the most useful tools in nanotechnology due to its acclaimed abilities in exploring surface topography, micro- and nanoscale manipulation and characterization. The nonlinear interaction between the cantileve ...

Bottom-up manufacturing of nanocrystalline diamond micro structures and components

Master thesis - F. Versluis, J.G. Buijnsters, U. Staufer, R.A. Norte

The exceptional material properties of bulk diamond like high stiffness, high thermal conductivity, wide optical transparency, chemical inertness and bio-compatibility make it the material of choice in many high-end applications. Most present-day diamond micro-devices are fabrica ...

Towards bottom-up fabrication of a BDD chip electrode

Master thesis - R.J.A. Brocken, J.G. Buijnsters, U. Staufer, J.F.L. Goosen

Boron-doped diamond (BDD) is an attractive electrode material. When sufficiently boron-doped, diamond has metal-like conductivity and in comparison with other electrode materials has several advantages, such as lowand stable background current, reduced biofouling, broad potentialwindow, corrosion resistance and chemical stability. However, current fabrication processes rely on top-down techniques, that often require cleanrooms and expensive micro fabrication techniques. This research focuses on a low-cost bottom-up fabrication technique by using an inkjet printing process to locally increase the substrate seeding density. Thin-film BDD can then be selectively grown into electrode geometries. The BDD electrodes can be used as more robust and better performing electrodes for detectingmicropollutants in environmental monitoring or for detecting biomarkers in saliva, sweat or blood, in health monitoring. Inkjet manufacturing is an emerging production process in micro fabrication. Due to its accuracy, material efficiency, and given that it is a digital process, inkjet printing is a strong candidate for bottom-up fabrication of low-cost and customizable BDD (micro)-electronics. Two inkjet printers were used to investigate themicro fabrication technique for a BDD chip electrode. A hacked desktop Epson printer was used to demonstrate the capabilities of selective seeding using ’diamond’ ink on silicon substrates and to grow patterned thin-film intrinsic diamond. However, the printer lacks the required control to produce continuous structures with high accuracy. A second method for selective seeding was employed by using a PIXDRO LP-50 commercial research printer, which has a high resolution, motion controlled print bed. With the application of surface treatments, such as oxygen plasma, on the silicon substrate and the development of different inks, continuous films of nanocrystaline diamond with line resolution of approximately 60 μm are produced in a final chemical vapor deposition (CVD) growth step. In addition, by loading the printer with a silver ink part of the diamond film has been coated with silver, which demonstrates that a reference electrodes or electrode leads can be manufactured with the same production technique. This research demonstrates the potential for the bottom-up fabrication of chip electrodes using the inkjet printing process. Furthermore, as this process is not limited to the production of BDD electrodes, it opens the path towards bottom-up fabrication of other (boron-doped) diamond sensor devices, such as gas sensors or 2D heaters.

Photo-patterned, pH-responsive hydrogel membranes for integrated fluid control

Master thesis - S.H. Soons, L. Sasso, P. Fanzio, U. Staufer, Matthijs Langelaar

To control fluid transport, microfluidic systems often make use of pressure driven flow and pneumatically actuated valves. However these require bulky external instrumentation. An integrated fluid control mechanism would make microfluidic systems more portable, closed and automated. The aim of this project was to create a pH-responsive membrane for integrated fluid control in microfluidic systems. pH-responsiveness will allow the membrane to interact directly with analytes in a microfluidic system. First pH-responsive materials and fluid control mechanisms to create a pH-responsive membrane were reviewed. Cross-linked polymer hydrogels with pH-dependent volumetric swelling were identified as the most suitable material for the membrane. These materials respond to changes in pH by large volumetric transitions, which creates potential for control over a wide range of flow rates. Furthermore they have an inherent interaction with water and are permeable to small molecules such as H+ ions. The material is synthesized from a liquid precursor that can be cured through photo-initiated free radical polymerization. We tested a system for measuring the pH response of the material that consisted of a hydrogel disk that was vertically constrained inside a fluidic channel. Due to this constraint, expansion only occurred in the lateral direction and could be measured using an optical microscope. Furthermore, we developed a method for manufacturing macro-porous hydrogel membranes that gives control over pore size, shape and position. A photo-lithography approach was used to pattern the membranes and thereby create pores, using a photo-mask that was manufactured on an office printer in a very fast and low-cost process. The resulting membranes had a thickness of 140-190 um and pore diameters of 100-400 um. The pore size was measured for environmental pH of 1.6 and 7.1, within this range the pores doubled in diameter. Furthermore the pH-responsive deformation ratio of the pores increased significantly with increasing curing time and decreasing pore diameter. The results suggest that there is a difference in material properties around the pores that develops due to a local difference in received exposure dose during curing. The fluidic properties and pH-response of the membrane can be adjusted to suit a specific application by changing the design, the curing time or the chemical composition of the membrane. The constrained disk system can then be used to measure and compare the pH-response of different potential materials.

Fabrication of polymer nanocomposites for application in luminescent solar concentrators

Master thesis - J.D.B. Endtz, U. Staufer, L. Sasso, J.F.L. Goosen, E. Mendes, A. Jung

The integration of luminescent nanoparticles into transparent polymer matrices opens the way to affordable, scalable and efficient luminescent solar concentrators. A key challenge in the fabrication is to prevent agglomeration of the nanoparticles as this will drastically reduce ...