Self-folding Microgrippers and Their Applications as BioMEM Systems

Self-actuating microtools have evolved to be more efficient as diagnostic biological microelectromechanical (bioMEM) systems because of their miniature and robust designs. One of these microtool designs, namely microgrippers, is fabricated and used with the purpose of single cancer cell and tumor lesion diagnostics. They are self-actuated tools that can be used tethered or untethered with many potential applications in the field of medicine. Self-folding microgrippers have different applications depending to their dimensions and designs. We utilized single cell microgrippers as micro-arrayed diagnosis tools by capturing mammalian cells in vitro without causing any damage. Since the microgripper design allows for nutrients in the environment to diffuse in and out of the cell between the gripper arms, the cells stay viable over 24 hours, which facilitates dynamic observations on the cells. We successfully detected specific molecules in a captured cell using surface-enhanced Raman spectroscopy (SERS). Additionally, thermally-responsive untethered grippers can be used as soft tissue sampling tools with high resolution compared to conventional biopsy forceps. The addition of a thin nickel film on the gripper arms provides better motion control in vivo and thus, better coverage of the sampling area. Although the efficiency of these grippers was proven in a statistical model, we designed an in vivo statistical sampling study to support this model. Finally, we implemented a biocompatible actuation mechanism, capable of keeping the gripper arms open until reaching a tissue wall. Potential applications of microgrippers are extensive. Depending on their dimension, design, and the fabrication materials used, it is possible to adapt them into any desired application. Therefore, they are one of the pioneer designs in microtool systems in medicine. In this thesis, I aim to give a review of different microgripper designs from other research teams and explain our design and its applications

Electrical cell manipulation in microfluidic systems

This dissertation reports on the development of devices and concepts for electrical and microfluidic cell manipulation. In the present context, the term cell manipulation stands for both cell handling and cell modification. The combination of microfluidic channels with micropatterned electrodes allows for the definition of highly localised chemical and electrical environments with spatial resolution comparable to the size of a cell. The devices fabricated in the frame of this thesis employ dielectrophoretic particle handling schemes such as deflection and trapping in pressure-controlled laminar flows to bring cells to – or immobilise them at – locations where cell altering electric fields or chemicals are present. The two concepts of dielectrophoretic cell dipping and cell immersion are introduced and experimentally shown for erythrocytes dipped into Rhodamine in flow, and for individually immobilised Jurkat cells immersed by Trypan Blue. Also, in-situ membrane breakdown in high intensity AC electric fields is optically assessed by efflux of haemoglobin (haemolysis) and by influx of nucleic stains or fluorescence-enhancing ions. The most advanced experiments are on-chip medium exchange followed immediately by electropermeablisation or electrodeformation. The majority of assays presented in this thesis are carried out in microfabricated glass-polymer-glass chips featuring top-bottom electrodes. The devices are fluidically controlled by external gas pressure bridging circuits. Experimental evidence of the unmatched precision of pressure bridging is given in the case of micrometric xy positioning of cells at the intersection of two perpendicular microfluidic channels. Further shown in this document are two methods of optical in-situ temperature measurements, important for bioinstrument characterisation. The two concepts of thermoquenching of a fluorescent dye and the original thermoprecipitation of "smart polymers" are used. The last part of this work deals with the innovative, conceptual engineering tool Liquid Electrode. The general concept and its advantages over solid-state electrodes are given, followed by numerical particle tracking in the case of the novel lateral nDEP particle deflection. The chapter on liquid electrodes concludes with preliminary experimental results of buffer swapping of cells in flow and of AC electropermeabilisation of erythrocytes at frequencies far below the cut-off frequency of corresponding solid-state microelectrodes

Self-powered mobile sensor for in-pipe potable water quality monitoring

Traditional stationary sensors for potable-water quality monitoring in a wireless sensor network format allow for continuous data collection and transfer. These stationary sensors have played a key role in reporting contamination events in order to secure public health. We are developing a self-powered mobile sensor that can move with the water flow, allowing real-time detection of contamination in water distribution pipes, with a higher temporal resolution. Functionality of the mobile sensor was tested for detecting and monitoring pH, Ca2+, Mg2+, HCO3-/CO32-, NH4+, and Clions. Moreover, energy harvest and wireless data transmission capabilities are being designed for the mobile sensor

Capturing, Analyzing and Collecting Adherent Cells Using Microarray Technologies

Effective separation of a particular cell of interest from a heterogeneous cell population is crucial to many areas of biomedical research including microscopy, clinical diagnostics and stem cell studies. Examples of such studies include the analysis of single cells, isolation of transfected cells and cell transformation studies. Biological technologies can have skewed results if cells outside of the type of interest are present. Additionally, in many instances the targeted cells are of low abundance with respect to the heterogeneous population. For these reasons, it is important to have a technique capable of identifying the desired cells, separating these cells from unwanted cells and collecting the marked cells for further analysis. Two biotools, referred to as micropallets and microrafts, have recently been introduced for sorting adherent cells. These devices comprise arrays of microelements weakly attached to a substrate. Following culture of adherent cells on the elements, individual microstructures are selectively detached from the array while still carrying the cells. These technologies have shown success in sorting single cells from small heterogeneous cell populations with high post sorting viabilities. However, previous device designs employed gravity-based collection methods and small microelement arrays which substantially reduced the collection yields, purities and sample sizes. In this dissertation new approaches are described for capturing, examining and isolating individual cells by micropallet and microraft technologies. Initially a new approach was developed to isolate released microstructures from the array employing magnetism. Microstructures were embedded with uniformly dispersed magnetic nanoparticles which allowed collection by an external magnet immediately following release. Application of a magnetic field permitted microstructure collection with high yield, precision and purity. This improved collection efficiency enabled isolation of very rare cell types. Large arrays constituting over 106 micropallets were developed along with imaging analysis software to identify and sort low abundance target cells. This system was employed to isolate breast cancer stem cells from a heterogeneous cell population and circulating tumor cells directly from peripheral blood. Additionally, an array-based cell colony replication strategy was established which allowed highly efficient colony splitting and sampling.Doctor of Philosoph