Lab-on-a-chip

A lab-on-a-chip (LOC) is a device that integrates one or several laboratory functions on a single integrated circuit (commonly called a "chip") of only millimeters to a few square centimeters to achieve automation and high-throughput screening. LOCs can handle extremely small fluid volumes down to less than pico-liters. Lab-on-a-chip devices are a subset of microelectromechanical systems (MEMS) devices and sometimes called "micro total analysis systems" (µTAS). LOCs may use microfluidics, the physics, manipulation and study of minute amounts of fluids. However, strictly regarded "lab-on-a-chip" indicates generally the scaling of single or multiple lab processes down to chip-format, whereas "µTAS" is dedicated to the integration of the total sequence of lab processes to perform chemical analysis. History After the invention of microtechnology (~1954) for realizing integrated semiconductor structures for microelectronic chips, these lithography-based technologies were soon

Resonant optical trapping in hollow photonic crystal cavities and its potential use for bacterial characterisation

Rita Therisod

During the last decade, the development of optofluidic chips has become a large field of research. The integration of nano and microstructures with microfluidics layers allowed for the miniaturisation of a number of tools traditionally used in laboratories and optofluidic systems found their main applications in lab-on-a-chip and sensing platforms. At the same time, optical tweezers have become the tool of choice for the trapping and the manipulation of nano and micrometer-sized objects, that can be inert (dielectric or metallic particles) or biological (proteins, bacteria, viruses,...). In this context, nanostructures are the ideal candidate for tweezers miniaturisation, thanks to their ability to strongly confine light in small volumes and hence to generate intense gradient forces. This work reports on the fabrication of an optofluidic chip based on a two-dimensional photonic crystal cavity and on its use in particle and bacteria differentiation. The cavity has a hollow design that maximises the overlap between the confined field and the trapped objects and it supports Self-Induced Back-Action effects that allow for reducing the trapping power (down to few microwatts) and to simultaneously acquire information of the trapped specimen. The system is excited in an end-fire setup and the detection is carried out by recording the light intensity transmitted through the photonic crystal. The fabrication process, that is entirely carried out in the Institue of Physics and in the Center of MicroNanoTechnology cleanrooms, is first detailed. For the cavity design normally used, typical quality factors of 10000 were obtained. Moreover, SU8 mode adaptors were developed to increase the coupling with lensed fibers and a microfluidic membrane presenting two injection channels is proposed for rapid switch between liquids. The trapping and the differentiation of 250 and 500 nm polystyrene is then presented. The differentiation can be achieved qualitatively by direct observation of the transmitted intensity records and quantitatively by the use of histograms and of statistical moments. Finally, the trapping of seven species of living bacteria is shown and their Gram-type is determined by the analysis of the induced transmission increase. This ability to probe the cell wall of bacteria in a fast, label-free and non-destructive way paves the way for applications in biological and biomedical environments.

EPFL2019

Development of a microfluidic on-chip reverse transcription module for the analysis of hematopoietic single stem cells

Viktoria Stepanova

Hematopoietic stem cells (HSCs) have a unique ability to self-renew and produce differentiated progeny throughout the entire life of the human body. However, present clinical use of HSCs in regenerative medicine is largely hindered by our limited understanding of the mechanisms that direct stem cell fate both in vivo and in vitro. Genetic profiling of single stem cells is an appealing method to gain a deeper understanding of these processes by dissecting the relationship between the cellular phenotype and its gene expression signature. To do so, classical methods rely on the use of bench-top assays which either lack the required efficiency for the analysis of low-copy transcripts such as transcription factors, or the ability to capture the dynamics of a stem cell population, for instance during cell division. Here, we report a novel microfluidic device for the on-chip reverse transcription (RT) of single stem cells coupled with a chip-to-world interface that enables reliable extraction of samples for virtually any bench-top assay. The designed microfluidic module allows the trapping of single cells, their lysis and mRNA capture, followed by solid-phase cDNA synthesis using the Dynabead® system. We have successfully validated and characterized all major stages of the on-chip RT protocol and obtained single-cell nested RT-PCR readouts with an efficiency superior to bench-top assays. Live single stem cells have also been extracted and analyzed via this method, thus demonstrating that the developed device can act as much as a Lab-on-a-Chip system as a micro-manipulator for single cell microfluidic handling. Furthermore, we have laid the foundations for the integration of our RT module with on-chip cell culture for automated stem cell progeny capture during division. Such a device will help to study heterogeneities not only within cell populations, but also within the progeny of a single cell.

2011

Development of a microfluidic on-chip reverse transcription module for the analysis of hematopoietic single stem cells

Viktoria Stepanova

2011

Resonant optical trapping in hollow photonic crystal cavities and its potential use for bacterial characterisation

Rita Therisod

EPFL2019

Resonant optical trapping in hollow photonic crystal cavities and its potential use for bacterial characterisation

Development of a microfluidic on-chip reverse transcription module for the analysis of hematopoietic single stem cells

Ferromagnetic particles for an improved heterogeneous bioassay performance on a digital lab-on-a-chip

Development of a microfluidic on-chip reverse transcription module for the analysis of hematopoietic single stem cells

Resonant optical trapping in hollow photonic crystal cavities and its potential use for bacterial characterisation

Ferromagnetic particles for an improved heterogeneous bioassay performance on a digital lab-on-a-chip