This paper presents topology optimization on general two-dimensional
manifolds for phenomena described by second-order partial differential
equations, where the material interpolation is implemented by using the
material distribution method. When a physical field is defined on a
two-dimensional manifold, the material interpolation is implemented on a
material parameter in the partial differential equation used to
describe the distribution of the physical field. When the physical field
is defined on a three-dimensional domain with its boundary conditions
defined on a two-dimensional manifold corresponding a surface or an
interface of this three-dimensional domain, the material density is used
to formulate a mixed boundary condition of the partial differential
equation for the physical field and implement the penalization between
two different boundary types. Based on the homeomorphic property of
two-dimensional manifolds, typical two-dimensional manifolds, e.g.,
sphere, torus, Möbius strip and Klein bottle, are included in the
numerical tests, which are used to demonstrate this topology
optimization approach for the design problems of fluidic mechanics, heat
transfer and electromagnetics.
The recent introduction of glassy carbon (GC) microstructures supported on flexible polymeric substrates has motivated the adoption of GC in a variety of implantable and wearable devices. Neural probes such as electrocorticography and penetrating shanks with GC microelectrode arrays used for neural signal recording and electrical stimulation are among the first beneficiaries of this technology. With the expected proliferation of these neural probes and potential clinical adoption, the magnetic resonance imaging (MRI) compatibility of GC microstructures needs to be established to help validate this potential in clinical settings. Here, we present GC microelectrodes and microstructures—fabricated through the carbon micro-electro-mechanical systems process and supported on flexible polymeric substrates—and carry out experimental measurements of induced vibrations, eddy currents, and artifacts. Through induced vibration, induced voltage, and MRI experiments and finite element modeling, we compared the performances of these GC microelectrodes against those of conventional thin-film platinum (Pt) microelectrodes and established that GC microelectrodes demonstrate superior magnetic resonance compatibility over standard metal thin-film microelectrodes. Specifically, we demonstrated that GC microelectrodes experienced no considerable vibration deflection amplitudes and minimal induced currents, while Pt microelectrodes had significantly larger currents. We also showed that because of their low magnetic susceptibility and lower conductivity, the GC microelectrodes caused almost no susceptibility shift artifacts and no eddy-current-induced artifacts compared to Pt microelectrodes. Taken together, the experimental, theoretical, and finite element modeling establish that GC microelectrodes exhibit significant MRI compatibility, hence demonstrating clear clinical advantages over current conventional thin-film materials, further opening avenues for wider adoption of GC microelectrodes in chronic clinical applications.
The Lab-on-a-Disc (LoaD) approach was conceived in the 1990s as a
sub-class of the more generic µTAS (from MicroTotalAnalysingSystems). The µTAS
concept was derived ~10 years earlier with the hope to make a complete
chemical and, therefore, also biological analysis of all type of liquids in an
integrated and automated way. The idea was to create a mini lab in a piece of glass
or even plastic by using the shrinkage of all channels and components to obtain
highly branched networks of unit operations that allow complex analyses. Most
modern desktop analysis machines (like glucose or haemoglobin) are based in
some sort on that idea. To move away from work benches with glasses and vials
that are handled by highly trained personnel and replace them by microchannels
and microchambers where one can perform simple diagnostics automatically, that triggered
the idea to make laboratory diagnostic outside of clinics. If the analysis could
be performed nearly semi-automatic outside of a clinic’s lab, would the patient
still have to come to the clinic for initial tests? Saving the patient the long
way to a real hospital, by placing a semi-automated diagnostic in the rural
communities, is especially valuable in developing countries were this might
take days. One obstacle in that endeavour was the need of precision pumps to
drive the liquids through the channels and often also the usage of complex
tubing, Lab-on-a-Disc circumvented the need of pumps by spinning the whole
microfluidic chip and using the resulting centrifugal forces to drive the
liquids. In the last two decades this led to a large variety of the diagnosable
diseases using LoaDs.
The original idea of a (µ)TAS system to chemically completely analyse a
liquid is and back in the 1980s already was performed much better by another
technique – the NuclearMagneticResonance (NMR) Analysis. NMR is based on the
modulation of an electromagnetic signal, by the content the liquid, allowing to
get information directly from its molecular composition. Many atoms i.e.
Hydrogen, when placed in a magnetic field and activated by an electromagnetic
wave of a specific frequency, answer by sending back a signal of the same
frequency (hence the name resonance). This signal is now not 100% at the same
frequency but it is modulated slightly by the magnetic fields caused by the
molecules present in the liquid. A spectral analysis of the signal in the
frequency domain, therefore, shows characteristic peaks that are fingerprints
of the molecules present in the liquid.
Since NMR can be seen as the real TAS system, can an integration of the
two not lead to a true µTAS system, ignoring for now the little flaw that the
NMR magnets are nearly 2 m high? Both systems use liquid analytes in
fairly small quantities (µl to ml). Also, the rotation is beneficial for both,
while it drives the LoaDs it is used in NMR to improve the signal quality in a
technology called magic angle spinning. Automation in NMR is done via a carousel
that loads the test tube sequentially into the machine, the handling of small
plugs of sample is one of the key technologies in LoaD and could, therefore,
improve the high throughput sample handling. The merging of these two very well-established
technologies will allow to improve sample handling in NMR significantly while
at the same time shrinking the needed sample volume.
Integration of Ex-vivo precision-cut liver slice (PCLS) culture with microfluidic NMR metabolomics
Bishnubrata Patra(1), Manvendra Sharma(1), Ruby Karsten (2), Maciej Grajewski (2), Sabeth Verpoorte (2), and Marcel Utz (1)
1 School of Chemistry, University of Southampton, UK 2 School of Pharmacy, University of Groningen, The Netherlands
ABSTRACT We present a novel microfluidic perfusion system for liver tissue slices that allows direct characterization of the perfusion fluid by micro nuclear magnetic resonance (NMR) spectroscopy and imaging. This system enables direct non-invasive observation of the metabolic processes on the liver slice in real time. Integration of a microfluidic system with high-performance NMR spectroscopy has been achieved with careful management of sensitivity and magnetic susceptibility effects to maintain spectral resolution. The system presented here combines excellent NMR performance with the ability to sustain the PCLS over several hours of perfusion.
INTRODUCTION Ex-vivo culture of tissue provides an alternative to animal models to study the effect of external factors like exposure to drugs, environmental changes, infection, and inflammation, requiring significantly less resources  and providing more detailed information. Observation of metabolism by NMR is well established. We present a microfluidic perfusion culture system for PCLS that allows direct NMR observation of the metabolite composition of the perfusate after contact with the slice using a home made transmission-line NMR probe .
EXPERIMENTAL The NMR setup and the perfusion chip are shown in figure 1. The microfluidic device (figure 1E) with the PCLS is sandwiched between polydimethylsiloxane(PDMS) membranes and chip holders. Culture medium is supplied with a syringe pump at a flow rate of 8 µl/min. Both oxygen and carbon dioxide are exchanged by diffusion through the PDMS membrane. The device containing PCLS is kept at physiological temperature bysupplying hot water from a water bath (figure 1C) through a micro pump ( figure 1B).
RESULTS AND DISCUSSION Murine PCLS were incubated in well plates at 37°C in 80% O2 and 5% CO2 after slicing. Their viability was ascertained by LDH leakage assay before the perfusion experiment at day 1. After 1-3 days of incubation, they were transferred into the perfusion system. NMR spectra were continuously recorded for up to 5 hours of perfusion. Incremental NMR spectra obtained over the course of the perfusion demonstrates stability of the system over several hours (figure 3). The proton NMR spectrum in Figure 4, averaged over the duration of the experiment, gives an indication of the quality of the spectral information. At least 20 different metabolites are clearly apparent from this spectrum; most prominently, glucose, alanine, glutamine, glutamate, valine, leucine, and isoleucine. A small lactate peak is visible t 1.32~ppm. After 5h of perfusion, viability of the slices was verified using ATP content/ µg of protein assay.
CONCLUSION These results demonstrate that PCLS can be kept viable in an NMR-compatible microfluidic system, while high-quality NMR data of the perfusate is extracted. This opens the way for further studies to explore the metabolic activity of slices exposed to various external stimuli.
ACKNOWLEDGEMENTS This research project is funded by the horizon 2020 Framework program of the European Union. The authors sincerely acknowledge the discussion with Prof. Peter Olinga regarding tissue slice culture.
REFERENCES  I. A. M. de Graaf, P. Olinga, M. H. de Jager, M. T. Merema, R. d Kanter, E. G. Van de Kerkhof, G. M. MGroothuis, Preparation and Incubation of Precision-Cut Liver and Intestinal Slices for Application in Drug Metabolism and Toxicity Studies. Nature Protocols 2010, 5 (9), 1540-1551.  M. Sharma, M. Utz, Modular Transmission Line Probes for Microfluidic Nuclear Magnetic Resonance Spectroscopy and Imaging. Journal of Magnetic Resonance 2019, 303, 75-81.
Saraí M. Torres Delgado, Jan G. Korvink1 and Dario Mager*
Karlsruhe Institute of Technology – IMT, Eggenstein – Leopoldshafen, 76344, Germany
Over the last decade centrifugal microfluidic platforms have been of increasing interest for use in decentralized bioanalytical testing such as point-of-care diagnostics. This technology is particularly powerful due to the inherent ability to centrifuge samples like the ones required for blood processing. However, while the LoaD technique compared to LOC, has simplified basic operations such as valving, pumping, metering, mixing and sample preparation, solutions to other arising needs, such as the integration of (active) operations, or the readout of a bioassay result, has proven more challenging to achieve when the platform is under continuous rotation, a characteristic inherent to their working principle. As anyone can foresee, power and signal cables cannot be connected to a rotating system, because they will twist, entangled, and finally, disconnect or brake, hampering the integration of actuators and/or detectors into the system. These components are needed for a sensitive, reliable, time-independent, fast, direct and continuous interaction with the microfluidic disc while spinning and, thereby, enhancing the success of LoaD systems.
Hence, here we present the design and development of a low cost, compact and portable platform that co- rotates with the microfluidics disc, called the “electrified Lab-on-a-Disc (eLoaD) platform” which includes all modules necessary for it to be used in any diagnostic assay. Because it requires power, wireless energy transmission was introduced into the system. Hence, the platform was designed and fabricated to behave as a wireless power receiver compatible with the Qi standard, better known for its use in wireless charging of consumer electronic devices. Since most envisaged applications will require a control unit that provides enough computational power, a way to record data and real-time bidirectional communication between the user and the ongoing experiment, the platform comprises an Arduino microcontroller, an SD-Card and a Bluetooth module. The inclusion of those modules renders a flexible platform, easy to operate for most users with backgrounds ranging from biology to engineering and compatible with concurrently emerging trends and standard technologies.
As any laboratory that operates on basic and specialized equipment, the capabilities of the proposed system can be augmented by the addition of a second electronic board plug-compatible to the eLoaD. This additional board referred to as Application Disc in Fig. 1 contains the application-specific sensors and actuators. Such scheme leads to a higher degree of interaction and enables more sophisticated concepts to be implemented both in the control as well as in the readout. The performance of the platform was tested under several sensing and actuation experiments (1-3), some of which will be presented at the conference.
Figure 1: Integration of the
wireless centrifugal system into conventional LoaD systems. A commercially
available Qi-compliant transmitter is inductively coupled to the eLoaD
platform. This fully integrated platform can control sensors and actuators
located on the Application Disc, which itself is simultaneously interacting
with the microfluidics disc. The disposable microfluidic disc and the reusable
Application Disc are typically designed for a particular application, whereas
the eLoaD platform, which implements the control logic, power, and
communication, is reused as a generic framework for all possible applications.
Interfacing of the eLoaD platform is enabled by Bluetooth communication, here
exemplary via an Android application program running on a portable device, and
from a PC running e.g. a LabVIEW script.
(1) S. M. Torres Delgado et al., Lab Chip, vol. 16, no. 20, pp. 4002-4011, 2016.
(2) S. M. Torres Delgado et al., Biosensors and Bioelectronics, vol. 109, pp. 214 – 223, 2018.
Multilayer flexible substrates offer a means to combine high lateral precision and resolution with roll-up processes, allowing layer-based manufacturing to reach into the third dimension. Here we explore this combination to achieve an otherwise hard-to-manufacture resonator geometry: the double-helix. The use of commercial flexPCB technology enabled optimal winding connections and a versatile adjustment to various operation fields, sample volumes and resonance numbers. The sensitivity of the design is shown to greatly benefit from the fabrication method, though optimal electrical connections and several radially-wound windings, and was measured to outperform an equivalent solenoid despite the known geometrical disadvantage.
University of Southampton, 2. School of Chemistry, University of Southampton
We report an in-situ, non-invasive approach to quantify oxygen partial pressure in microfluidic lab-on-a-chip (LoC) devices. LoC systems provide a versatile platform to culture biological systems. As they allow a detailed control over the growth conditions, LoC devices are finding increasing applications in the culture of cells, tissues and other biological systems . Integrated microfluidic NMR spectroscopy  allows non-invasive monitoring of metabolic processes in such systems. Quantification of oxygen partial pressure would help ensuring stable growth conditions, and provide a convenient means to assess the viability of the cultured system. However, oxygen, one of the most important metabolites, cannot be quantified using either proton or carbon NMR spectroscopy. As is well known, the oxygen partial pressure can be determined by MRI in vivo by measuring the 19F spin-lattice relaxation time of perfluorinated agents . Here, we show that the oxygen partial pressure in microfludic devices of 2.5 μl can be quantified using the 19F spin-lattice relaxation rate of perfluorinated tributylamine. The compound is added to the aquous perfusion medium in the form of micrometer-sized droplets. Our set up comprises a microfluidic device and a PDMS layer sandwiched between two 3D printed holders. The droplet emulsion is delivered via a syringe pump and carbogen is delivered through a separate channel. The semi- permeable PDMS layer acts as a diffusion bridge between the liquid and gas channels, allowing for oxygen to diffuse into the emulsion. T1 is obtained through standard inversion recovery experiments detected using a home-built transmission-line probe. Due to the non-toxic nature of droplet emulsion, it can be easily incorporated into the perfusion fluid allowing for quantification of tissue oxygen levels.
References:  Gracz et al., Nature Cell Biology 17, 340–349, 2015.  M.Sharma, M.Utz, J.Mag.Res 303, 75-81, 2019.  R.Manson et al., Magnetic Resonance in Medicine 18, 71-79, 1991.
resonance (NMR) is an analysis technique which is widely used in physics,
medicine and chemistry. As NMR is a non-invasive and non-destructive method, it
is used to image soft tissue inside the human body in the form of Magnetic
resonance imaging (MRI). Conventional liquid-state NMR spectroscopy is usually performed
on 200-800 microliter sample in a 5-10 millimeter diameter tube. Although
conventional NMR is successfully used for a variety of applications, many
problems cannot be adequately addressed by it. For example, bodily fluids from
small animals are usually available in much smaller quantities compared to the
sample volumes required by conventional NMR.
a well-established field for manipulation of small sample volumes in microliter
to nanoliter range. Due to small sample volumes, physical conditions for a
sample can be precisely controlled with minimum resources. NMR can be used to
study these systems for various chemical or biological processes.
systems are usually planar in geometry as oppose to conventional NMR sample
holders which are cylindrical in shape. To study microfluidic systems with NMR,
new setups tailored to specific needs are required.
developed a platform that can study generic microfluidic setups with NMR. This
new setup requires 100 times less sample volume compared to conventional liquid-state
NMR. The sample is held in a planar microfluidic chip made from plastic
materials. The microfluidic chip can be used as a passive sample holder or a flow
can be induced to supply different liquids. Gases can be dissolved in liquids
on the chip for chemical reaction or oxygen supply to biological systems. The
temperature at the chip can be tightly controlled to study different physical
conditions. As the chip is placed in the NMR detector all the systems can be
studied in real-time in their native environment. The setup has already been
used for various experiments including reaction monitoring, micro-imaging of
mouse liver tissue slices, and metabolic studies of mammalian cells.
In this prospective paper we consider the opportunities and challenges of miniaturized nuclear magnetic resonance. As the title suggests, (irreverently borrowing from E.F. Schumacher’s famous book), miniaturized NMR will feature a few small windows of opportunity for the analyst. We look at what these are, speculate on some open opportunities, but also comment on the challenges to progress.
Ruby E.H. Karsten, Nikolaas V.J.W. Krijnen, Maciej Grajewski, Elisabeth Verpoorte, Peter Olinga
Groningen Research Institute of Pharmacy, University of Groningen, Groningen, The Netherlands
SLAS Europe 2019
BelTox, Brussels 2019
cholestasis (DIC), an adverse drug reaction, has a complex disease mechanism
with no good model for early
detection in drug development.
developing an ex vivo mouse model
based on precision-cut liver slices (mPCLS) to study DIC. We incubate PCLS for 48h with glibenclamide
(a cholestatic drug). Cholestasis is ascertained by comparing control slices to
slices treated with drug, with and without an optimized bile acid (BA) mix. We studied
mPCLS viability and gene expression of BA transporters.
Non-toxic glibenclamide concentrations led to greater gene expression of basolateral and canalicular bile export transporters, the latter with a higher increase in the presence of BA mix. This study is the first that relates gene expression data to early DIC development in mPCLS. Once optimized, mPCLS will be incubated in a microfluidic device to monitor DIC onset in real time. We will use this model to elucidate disease mechanisms and perform drug toxicity screening.
Graaf IAM, Olinga P, de Jager MH, Merema MT, de Kanter R, van de Kerkhof EG,
e.a. Preparation and incubation of precision-cut liver and intestinal slices
for application in drug metabolism and toxicity studies. Nat Protoc. september