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Live-cell microscopy is crucial for biomedical studies and clinical tests. The technique is, however, limited to few laboratories due to its high cost and bulky size of the necessary culture equipment. In this study, we propose a portable microfluidic-cell-culture system, which is merely 15cm×11cm×9cm in dimension, powered by a conventional alkali battery and costs less than USD 20. For long-term cell culture, a fresh culture medium exposed to 5% CO2 is programmed to be delivered to the culture chamber at defined time intervals. The 37 °C culture temperature is maintained by timely electrifying the ITO glass slide underneath the culture chamber. Our results demonstrate that 3T3 fibroblasts, HepG2 cells, MB-231 cells and tumor spheroids can be well-maintained for more than 48 h on top of the microscope stage and show physical characters (e.g., morphology and mobility) and growth rate on par with the commercial stage-top incubator and the widely adopted CO2 incubator. The proposed portable cell culture device is, therefore, suitable for simple live-cell studies in the lab and cell experiments in the field when samples cannot be shipped.

The soluble fraction of aerosol particulate matter containing trace metals has the potential to engender toxicity and exacerbate the adverse health effects of particulate matter. In this study, an inertial-impaction-based fluidic chip integrated with electrochemical detection was developed to achieve high collection efficiency and measurements of the bioaccessible metal fraction at the nanogram level. The average collection efficiency for ultrafine and fine particles larger than 50 nm, obtained at a flow rate of 2.5 L/min, was above 70%. The detection ranges of aerosol soluble copper depended on the collection duration and airflow rate. At a working flow rate of 3.1 L/min and collection efficiency of 70%, the microsystem was capable of detecting Cu concentrations above 53 ng/m3, 32 ng/m3 and 8 ng/m3 with 3 h, 5 h and 20 h collection periods, respectively, which were in the range of reported atmospheric concentrations. The detection ratio of real-world samples (i.e. PM10-like aerosol) was 100 ± 14%, indicating excellent aerodynamic collection and reliable electrochemical detection. The collection and sensing performance of the microsystem demonstrates a new step towards an online, mobile, low-cost, and miniaturized routine monitoring system for bioaccessible metals and possibly other soluble components in the aerosols., Sensors and Actuators B: Chemical, 351, ISSN:0925-4005

Prompt and effective antimicrobial therapy is crucial for the management of patients with severe bacterial infections but is becoming increasingly difficult to provide due to emerging antibiotic resistance. The traditional methods for antibiotic susceptibility testing (AST) used in most clinical laboratories are reliable but slow with turnaround times of 2 to 3 days, which necessitates the use of empirical therapy with broad-spectrum antibiotics. There is a great need for fast and reliable AST methods that enable starting targeted treatment within a few hours to improve patient outcome and reduce the overuse of broad-spectrum antibiotics. The multiplex fluidic chip for phenotypic AST described in the present study may enable data on antimicrobial resistance within 2 to 4 h, allowing for an early initiation of appropriate antibiotic therapy., Many patients with severe infections receive inappropriate empirical treatment, and rapid detection of bacterial antibiotic susceptibility can improve clinical outcome and reduce mortality. To this end, we have developed a multiplex fluidic chip for rapid phenotypic antibiotic susceptibility testing of bacteria. A total of 21 clinical isolates of Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were acquired from the EUCAST Development Laboratory and tested against amikacin, ceftazidime, and meropenem (Gram-negative bacteria) or gentamicin, ofloxacin, and tetracycline (Gram-positive bacteria). The bacterial samples were mixed with agarose and loaded in an array of growth chambers in the chip where bacterial microcolony growth was monitored over time using automated image analysis. MIC values were automatically obtained by tracking the growth rates of individual microcolonies in different regions of antibiotic gradients. Stable MIC values were obtained within 2 to 4 h, and the results showed categorical agreement with reference MIC values as determined by broth microdilution in 86% of the cases.

This thesis is part of the general application framework of single cell analysis. In order to improve the selectivity of single cell sorting, FEMTO-ST teams propose to control in closed loop the trajectories of the cells in real time during their journey in the chips dedicated to sorting. In this context, my thesis work focuses on an innovative method for real-time detection of cell position, directly integrated into chips and based on the physical principle of impedance measurement.When a cell passes through a microchannel, it changes the measurable impedance between electrodes placed on the edges of the channel.A generic method for formulating impedance variations as a function of particle position has been proposed (direct model). A method for estimating the position of a particle based on impedance measurements has also been proposed (inverse model). It uses an extended Kalman filter, allowing data from several pairs ofelectrodes to be merged, and exploiting available information such as measurement noise distribution and particle dynamic model. The validation of the method was carried out on an experimental bench that was developed during this thesis and on numerical simulations.This work shows the relevance of using impedance measurement to build a position sensor for particles immersed in a microchannel. This method is an alternative to the use of optical microscopes and has the advantage of being very compact.; Cette thèse s’inscrit dans le cadre applicatif général de l'analyse de cellules uniques. Afin d’améliorer la sélectivité du tri de cellules uniques, les équipes de FEMTO-ST proposent de contrôler en boucle fermée les trajectoires des cellules entemps réel pendant leur trajet dans les puces dédiées au tri. Dans ce cadre, mes travaux de thèse portent sur une méthode novatrice de détection en temps-réel de la position des cellules, directement intégrée aux puces et basée sur le principephysique de la mesure d'impédance.Lors du passage d’une cellule dans un microcanal, celle-ci vient modifier l’impédance mesurable entre des électrodes placées sur les bords du canal.Une méthode générique permettant de formuler les variations d'impédance en fonction de la position de la particule été proposée (modèledirect).Une méthode d'estimation de la position d’une particule reposant sur les mesures d’impédance a également été proposée (modèle inverse). Celle-ci exploite un filtre de Kalman étendu, permettant la fusion de données en provenance de plusieurspaires d'électrodes, et exploitant les informations disponibles telles que la distribution du bruit de mesure et le modèle dynamique de la particule.La validation de la méthode a été effectuée sur un banc expérimental qui a été développé lors de cette thèse et sur des simulations numériques.Ces travaux montrent la pertinence d’exploiter l’impédancemétrie pour construire un capteur de position de particules immergées dans un microcanal. Cette méthode est une alternative à l’utilisation de microscopes optiques et présente l’avantage d’une grande compacité.

We describe a novel stacked split-ring type microwave (MW) resonator that is integrated into a 10 mm by 10 mm sized microfluidic chip. A straightforward and scalable batch fabrication process renders the chip suitable for single-use applications. The resonator volume can be conveniently loaded with liquid sample via microfluidic channels patterned into the mid layer of the chip. The proposed MW resonator offers an alternative solution for compact in-field measurements, such as low-field magnetic resonance (MR) experiments requiring convenient sample exchange. A microstrip line was used to inductively couple MWs into the resonator. We characterised the proposed resonator topology by electromagnetic (EM) field simulations, a field perturbation method, as well as by return loss measurements. Electron paramagnetic resonance (EPR) spectra at X-band frequencies were recorded, revealing an electron-spin sensitivity of View the MathML source3.7·1011spins·Hz-1/2G-1 for a single EPR transition. Preliminary time-resolved EPR experiments on light-induced triplet states in pentacene were performed to estimate the MW conversion efficiency of the resonator.

Immunomagnetic separation has been widely used for the separation and concentration of foodborne pathogens from complex food samples, however it can only handle a small volume of samples. In this paper, we presented a novel fluidic device for the specific and efficient separation and concentration of salmonella typhimurium using self-assembled magnetic nanoparticle chains. The laminated sawtooth-shaped iron foils were first mounted in the 3D-printed matrix and magnetized by a strong magnet to generate dot-array high gradient magnetic fields in the fluidic channel, which was simulated using COMSOL (5.3a, Burlington, MA, USA). Then, magnetic nanoparticles with a diameter of 150 nm, which were modified with the anti-salmonella polyclonal antibodies, were injected into the channel, and the magnetic nanoparticle chains were vertically formed at the dots and verified using a fluorescence inverted microscope. Finally, the bacterial sample was continuous-flow injected, and the target bacteria could be captured by the antibodies on the chains, followed by gold standard culture plating to determine the amount of the target bacteria. Under the optimal conditions, the target bacteria could be separated with a separation efficiency of 80% in 45 min. This fluidic device could be further improved using thinner sawtooth-shaped iron foils and stronger magnets to obtain a better dot-array magnetic field with larger magnetic intensity and denser dot distribution, and has the potential to be integrated with the existing biological assays for rapid and sensitive detection of foodborne bacteria.

We present a new peristaltic micropump offering three key features: (i) a disposable pump body and a re-useable actuator unit, (ii) an intrinsic normally-closed mechanism blocking unintended liquid flows up to a pressure of 100 kPa and (iii) a backpressure independent pump performance up to 40 kPa. The modular concept basing on a re-usable actuator unit and a low-cost disposable microfluidic chip enables an easy and cost-efficient exchange of all contaminated parts after use, which addresses especially the needs in the health care sector. The intrinsic normally-closed feature blocks liquid flow in both directions up to a pressure difference of 100 kPa when the electric power is off. The micropump is actuated in a peristaltic manner by three piezostack actuators. Up to a frequency of 15 Hz the pump rate increases linearly with operation frequency leading to a pump rate of 120 μL/min. This was proved for an operation voltage of 140 V by pumping water. In addition the pump rate is independent on backpressure up to 40 kPa and shows a linear decrease for higher pressure differences. The maximum achievable backpressure at zero flow rate was extrapolated to be 180 kPa. As for all peristaltic micropumps, the pump is bidirectional, e.g. the pump direction can be changed forward to reverse mode.