New techniques which afford the rapid screening of cells to determine the presence of diseases are essential to provide efficient and effective future treatments and to improve patient health outcomes across a broad spectrum of disease states. In the last 30 years, the introduction of micro electro mechanical systems (MEMS) has prompted substantial research to develop miniaturised disease screening equipment based on microfluidic technologies. Such technologies aim to enhance point of care (POC) diagnosis, as a rapid clinical alternative to biopsy or blood tests (results typically between 2-10 days). The encapsulation of cells together with expensive functionalised particles, called Drop-seq, is currently regarded as the most effective existing single diagnostic platform approach to derive the genome of cells affected by a variety of diseases down to the single-cell level. Although this Drop-seq technology represents the current state of the art, it suffers from a serious drawback as only approximately 10% of the cells involved are encapsulated together with a single functionalised expensive particle. This loss of over 90% of cells and expensive particles in the sensing process is a serious limitation for the screening of rare cells such as circulating tumour cells of which there are only 1/1000 in a typical blood sample. Earlier and more accurate detection of potentially fatal diseases would represent a remarkable advance in healthcare, with substantive reductions in the ongoing health cost burden and significant improvements to the quality of life of each affected individual. The research proposed aims to exploit advances in viscoelastic flow technology to increase the efficiency of the Drop-seq technique to an unprecedented 100%. To achieve this transformative result the planned work will establish a means to ensure the equal-spacing of cells and functionalised particles before they approach the encapsulation area. This ensures that a single cell is encapsulated with a single particle, in a single droplet (a process referred to herein as deterministic encapsulation). Thus, the Drop-seq becomes deterministic when the frequency of droplet formation is synchronised with the frequency of particles and cells approaching the encapsulation area. Henceforth, the efficiency of the Drop-seq technology becomes 100%, rather than the mere 10% currently obtained. The project will be carried out in conjunction with an industry partner that is recognised as the world leader in the design and manufacture of pioneering microfluidic products. The objectives of the research are as follows: (1) Achieving cell ordering in straight channel; (2) Achieving continuous formation of viscoelastic droplets with uniform sizes and shapes; (3) Encapsulation of single particles in viscoelastic droplets with uniform size distribution; (4) Encapsulation of single cells in viscoelastic droplets. The research, which will achieve unprecedented disease detection capability, has substantive potential impacts, both in terms of healthcare outcomes and economic benefits. It will provide a basis for transforming the accuracy of detection for diseases such as lung, prostate, breast and bowel cancers, which currently account for more than half the types of cancer and lead to premature death. Beneficiaries will therefore include patients and healthcare professionals. Specifically, the POC testing approach has special relevance to healthcare professional working in remote locations. Examples include GP surgeries, clinics in remote locations or even within pharmacies. Our project partner is well placed to drive the research outputs to commercialisation and economic gain- on a global basis. Furthermore, widespread technical benefits in diverse fields including Process Engineering and Advanced Manufacturing may be anticipated to arise from enhanced knowledge of the innovative uses of viscoelastic flows within microfluidic settings.

Label-free detection of circulating tumour cells (CTCs) is considered to be one of the holy grails of biosensing. CTCs are malignant cells shed into the bloodstream from a tumour, which have the potential to establish metastases. The separation and subsequent characterization of these cells is of vital importance for cancer diagnosis and development of personalized cancer therapies. Biochemical CTC separation methods have proven to be highly inefficient and, therefore, preventive screening by sole blood analysis is currently not reliable. Microwave-to-terahertz dielectric measurements were successfully used for the identification of cancer cells; their capability for tumour tissue imaging is clinically established as a viable alternative to X-rays and MRI. The frequency range from 10 GHz up to about 1 THz is extremely promising for the detection of single tumour cells. Due to the diminishing cell membrane polarization effects, the cell membrane becomes transparent, but cell scattering is still negligible, in contrast to that found in the visible and near/medium-infrared range. Due to the high electromagnetic absorption of water up to about 1 THz, electromagnetic resonators with high quality factors and highly concentrated electric field within a small integrated microfluidic reservoir (previously demonstrated by the team), which essentially contains one cell at a time, represent an ideal system for fast and accurate dielectric measurements. This is because the single cell lies within their natural liquid environment. In order to tackle the problem of extremely low abundance of CTCs in blood samples, we intend to combine microfluidic separation techniques with integrated microwave-to-terahertz resonators on one chip or as a multichip combination, aiming towards a lab-on-chip approach for clinical applications. In order to achieve this ambitious goal, within this three-year project, we suggest a multidisciplinary approach, based on the expertise of the associated members of Imperial's Centre for Terahertz Science and Engineering (made up of academics and researchers from the Depts. of Materials, Electrical and Electronic Engineering and Physics), along with selected groups from dedicated areas of Life Sciences (which includes cancer cell biology and cell biosensing), plus the expertise of oncologists from Imperial's Faculty of Medicine. A variety of tumour cell suspension of defined concentration based on whole blood, serum or water being derived from a murine model will be our gold standard approach for the generation of a database of dielectric properties of different types of tumour cells, for the optimization of different sensor chip approaches, and for the development of cell detection methods. As a key milestone, towards the end of the project, we will demonstrate CTC detection in human blood samples. As the main engineering challenge of this project, three different electromagnetic resonator approaches will be investigated, based on our previous work on silicon MEMS technology for nanolitre liquid measurements: dielectric resonators, photonic crystals and spoof plasmon-based metamaterials. Advanced micro- and nano-machining techniques like deep reactive ion etching, e-beam lithography and focussed ion-beam etching will be employed for the manufacturing of fully-integrated (sub-) THz resonator-microfluidic systems. On the way towards the grand challenge of CTC detection, we intend to investigate two potential applications, which may generate clinical impact on a shorter timescale: Label-free detection of leukaemia cells within a murine model and bladder cancer cell detection in human urine samples. In both cases, the expected cell abundance is much higher than in the case of CTC, but the methods of dielectric cell recognition are identical to CTC detection. Follow-up projects including clinical studies plus stronger involvement of industry are likely to be launched during the time-span of this project.

How liquids wet solid surfaces is of fundamental importance to a wide-range of scientific disciplines and technological applications from creating thin films on semiconductor wafers, through adhesion and coating of surfaces, to effective droplet deposition and mixing on DNA microarrays. Electrostatic fields can alter how effectively a liquid wets a solid surface. In recent years uniform electric fields have been used to control and manipulate droplets of conducting (ion containing) liquids, typically a salt solution, by using the liquid-solid contact area as one electrode in a capacitive structure - so called electrowetting. This has led to new voltage controlled variable focus liquid lenses, liquid-based electronic paper and droplet-based microfluidic systems. The key to electrowetting is the ability of an applied voltage to reversibly increase the effective hydrophilicity of a solid surface and reduce the contact angle of the droplet without altering the surface chemistry. However, many liquids of interest are not conducting and the need for a sandwich-style capacitive structure and direct physical contact to the liquid limits its range of applicability. In this project we create a new method of controlling hydrophilicity and oleophilicity of materials by using the dielectric properties of liquids, but with the effects localized to an interface. Unllike electrowetting which focuses on the ions, our method focuses on the dipoles in a liquid. Using a non-uniform electric field generates unequal forces on the two ends of the dipole. The resulting dielectrophoretic force can result in movement and redistribution of the liquid into the areas of highest field gradient. The basis of our project is the understanding that when the liquid has solid-liquid, liquid-vapor or liquid-liquid interfaces, dielectric energy changes can be coupled to surface free energy changes. With a suitable decaying electric field, the effects of liquid dielectrophoresis can be confined to either the solid-liquid interface or to the liquid-vapor (or liquid-liquid) interface and can be used with a non-conducting liquid. By using microfabricated interdigitated electrodes a decaying, and hence non uniform, electric field can be created above a solid surface. For a droplet thicker than the decay length of the electric field, the major change of the surface energy compensating liquid dielectrophoretic energy changes is via a change in the contact area with a solid and so this can be a method of reversibly controlling the contact angle and, hence, the hydro- and oleo- philicity of a surface. For a thin liquid film the major change of the surface energy compensating liquid dielectrophoretic energy changes is via a change in the shape of the liquid-vapor (or liquid-liquid) interface and so, in this case, it becomes a method for shaping a liquid surface. In this method of localizing the effects of liquid dielectrophoresis to an interface the contrast to electrowetting is that, 1. the electric fields are non-uniform; 2. the electric fields are generated by surface microfabricated co-planar rather than sandwich electrode structures; 3. the forces act upon the dipoles in the liquids, which can therefore be non-conducting (or conducting), rather than upon ions of conducting liquids; 4. the method does not suffer from saturation of the contact angle and so can be used to produce liquid films. The research in this project seeks to establish an approach to wetting that allows conducting and non-conducting liquids to be manipulated using electric fields in a manner complementary to electrowetting. The project will provide the understanding needed to allow future development of novel droplet microfluidic, liquid microactuation, liquid-based optics and displays. The project includes industrial partners who have expertise in the development and commercialisation of microfluidic liquid handling, lab-on-chip devices, display devices and optofluidic systems.