Circulating Tumor Cells (CTC) have the potential to be used clinically as a diagnostic tool and a treatment tool in the field of oncology. As a diagnostic tool, CTC may be used to indicate the presence of a tumor before it is large enough to cause noticeable symptoms. As a treatment tool, CTC isolated from patients may be used to test the efficacy of chemotherapy options to personalize patient treatment. One way for tumors to spread is through metastasis via the circulatory system. CTC are able to exploit the natural leukocyte recruitment process that is initially mediated by rolling on transient selectin bonds. Our capture devices take advantage of this naturally occurring recruitment step to isolate CTC from whole blood by flowing samples through selectin and antibody-coated microtubes. Whole blood was spiked with a known concentration of labeled cancer cells and then perfused through pre-coated microtubes. Microtubes were then rinsed to remove unbound cells and the number of labeled cells captured on the lumen was assessed. CTC were successfully captured from whole blood at a clinically relevant level on the order of 10 cells per mL. Combination tubes with selectin and antibody coated surface exhibited higher capture rate than tubes coated with selectin alone or antibody alone. Additionally, CTC capture was demonstrated with the KG1a hematopoietic cell line and the DU145 epithelial cell line. Thus, the in vivo process of selectin-mediated CTC recruitment to distant vessel walls can be used in vitro to target CTC to a tube lumen. The biomolecular coatings can also be used to capture CTC of hematopoietic and epithelial tumor origin and is demonstrated to sensitivities down to the order of 10 CTC per mL. 
In a related study aimed at reducing the blood borne metastatic cancer load, we have shown that cells captured to a surface can be neutralized by a receptor-mediated biochemical signal. In the proposed method we have shown that using a combined selectin and TRAIL (TNF Related Apoptosis Inducing Ligand or Apo 2L) functionalized surface we are able to kill about 30% of the captured cells in a short duration of one hour whereas it took about 4 hours to kill the same proportion of cells without flow on a similarly functionalized surface. Here we have taken the approach a step further by showing that with very small doses of chemotherapeutic agents like bortezomib, we can increase the kill rate of CTC, thus allowing the device to function in scenarios where the patient is undergoing treatment. We show here that, with leukemic cells treated with bortezomib we are able to kill about 41% of the captured cells.

We investigate high-modulus degradable materials intended to replace metals in biomedical applications. These are typically composites comprising a polylactide (PLA) matrix reinforced with phosphate glass fibres, which provide reinforcement similar to E-glass but are entirely degradable in water to produce, principally, calcium phosphate. We have made composites using a variety of fibre architectures, from non-woven random mats to unidirectional fibre tapes. Flexural properties in the region of 30 GPa modulus and 350 MPa strength have been achieved – directly comparable to quoted values for human cortical bone. In collaboration with other groups we have begun to consider the development of foamed systems with structures mimicking cancellous bone and this has shown significant promise. The fibres in these foamed structures provide improved creep resistance and reinforcement of the pore walls. To date the materials have exhibited excellent cellular responses in vitro and further studies are due to include consideration of the surface character of the materials and the influence of this on cell interaction, both with the composites and the glass fibres themselves, which show promise as a standalone porous scaffold.

The water-conducting network of capillaries in vascular plants has evolved over hundreds of millions of years in order to be able to cope with bubble clogging, a problem which also affects modern microfluidic devices. Decades of anatomical studies have revealed that plants growing in habitats in which the formation of bubbles, or emboli, is likely to be a frequent occurrence often have various forms of geometrical sculpturing on the internal surfaces of the xylem conduits. The possible function of such wall sculpturing has long been the subject of speculation. We have investigated the hypothesis that wall sculpturing is a functional adaptation designed to increase the wettability of the walls of xylem conduits, an effect which could be described as the inverse of the well-known lotus-effect. Our results show that wall sculpturing does enhance wettability. Importantly, theoretical calculations reveal that the geometric parameters of various types of wall sculpturing are such that the resulting surfaces are sufficiently rough to enhance wettability, but not significantly rougher. The results provide an appealing answer to the long-standing debate on the function of wall sculpturing in xylem conduits, and may provide biomimetic clues for new approaches to the removal of bubbles in microfluidic channels.

We have carried out an experimental study of liquid drop impact on superhydrophobic substrates covered by a carpet of chemically coated nano-wires. The micro-structure of the surface is similar to some biological ones (Lotus leaf for example). In this situation the contact angle can then be considered as equal to 180 degrees, with no hysteresis. Due to its initial inertia, the drop experiences a flattening phase after it hits the surface, taking the shape of a pancake. Once it reaches its maximal lateral extension, the drop begins to retract and bounces back. We have extracted the lateral extension of the drop, and we propose a model that explains the trend. We find a limit initial velocity beyond which the drop protrudes into the nano-wire carpet. We discuss the relevance of practical issues in terms of self-cleaning surfaces or spray-cooling.

It is well known that surface roughness has a very important effect on superhydrophobicity. The Wenzel and Cassie-Baxter models, which correspond to the homogeneous and heterogeneous wetting respectively, are currently primary instructions for designing superhydrophobic surfaces. However, the particular drop shape that a drop exhibits might depend on how it is formed. A water drop can occupy multiple equilibrium states, which relate to different local minimal energy. In some cases, both equilibrium states can even co-exist on a same substrate. Thus the apparent contact angles may vary and have different values. We discuss how the Wenzel and Cassie-Baxter equations determine the homogeneous and heterogeneous wetting theoretically. Contact angle analysis on hierarchical surface structure and contact angle hysteresis has been put specific attention. In particular, we study the energy barrier of transition from Cassie-Baxter state to Wenzel state, based on existing achievement by previous researchers, to determine the possibility of the transition and how it can be interpreted. It has been demonstrated that surface roughness and geometry will influence the energy required for a drop to get into equilibrium, no matter it is homogeneous or heterogeneous wetting.

Wetting and spreading processes which involve surfactant solutions are widely used in numerous industrial and practical applications nowadays. The performance of different non-ionic surfactants may vary significantly and so far superspreader solutions show the most promising spreading ability. The addition of trisiloxane surfactants to water was proven to enhance wetting, even on hydrophobic surfaces, on which conventional surfactants seem to have little or no effect. Although these extraordinary surfactants have been extensively studied over recent years, complete understanding of their underlying mechanisms and a suitable mathematical model are still lacking. Here we present a possible explanation for the impressive performance of trisiloxane, which is compared to wetting enhancement of a conventional surfactant. Additionally, we will explain why the hydrophobicity of the surface is a crucial factor for the spreading phenomenon. Light will be also shed on the effect of the pH of the solution to which surfactants are added. Finally, we will investigate long-term effects of the water environment on trisiloxane wetting ability and discuss if ageing may significantly affect their performance.

We describe a few mathematical tools which allow to investigate whether air-water interfaces exist (under prescribed conditions) and are mechanically stable and temporally persistent. In terms of physics, air-water interfaces are governed by the Young-Laplace equation. Mathematically they are surfaces of constant mean curvature which represent solutions of a nonlinear elliptic partial differential equation. Although explicit solutions of this equation can be obtained only in very special cases, it is–under moderately special circumstances – possible to establish the existence of a solution without actually solving the differential equation. We also derive criteria for mechanical stability and temporal persistence of an air layer. Furthermore we calculate the lifetime of a non-persistent air layer. Finally, we apply these tools to two examples which exhibit the symmetries of 2D lattices. These examples can be viewed as abstractions of the biological model represented by the aquatic fern Salvinia.

Sea urchin spines were chosen as a model system for biomimetic ceramics obtained using starch-blended slip casting. Porous alumina ceramics with cap-shaped layers with different alternating porosities were found to have superior fracture behavior under bulk compression compared to ceramics with uniform porosity. They fail in a cascading manner, absorbing high amounts of energy during extended compression paths. The porosity variation in an otherwise single phase material mimicks the architectural microstructure design of sea urchin spines of Heterocentrotus mammillatus, which are promising model materials for impact protection.

Biological tiny structures have been observed on many kinds of surfaces such as lotus leaves and insect wings, which enhance the hydrophobicity of the natural surfaces and play a role of self-cleaning. We presented the fabrication technology of a superhydrophobic surface using high energy ion beam. Artificial insect wings that mimic the morphology and the superhydrophobocity of cicada’s wings were successfully fabricated using argon and oxygen ion beam treatment on a polytetrafluoroethylene (PTFE) film. The wing structures were supported by carbon/epoxy fibers as artificial flexible veins that were bonded through an autoclave process. The morphology of the fabricated surface bears a strong resemblance to the wing surface of a cicada, with contact angles greater than 160?, which could be sustained for more than two months.

The paper presents a detailed analysis of experimental data in order to characterize the elastic properties of arteries. Such analysis would provide a good basis for evaluation of biomimetic vascular grafts. Since the latter needs to exhibit similar properties of native tissue, it is important to accurately characterize the biomimetic sample in a large range of applied stresses. The stress-strain properties vary according to the specific pathology (e.g. arteriosclerosis, aneurism) and the tissue graft must be chosen correctly. Two models are proposed in this paper on the stress-strain characteristics. An extension for frequency-domain analysis is provided for one of the models. The comparison between vascular grafts and native tissue for carotid and thoracic arteries in pigs are in good agreement with results from literature. The proposed experimental method offers suitable parameters for identifying models which characterize both elasticity and stiffness properties of the analyzed tissues (stress-strain). The proposed models show good performance in characterizing the intrinsic material properties.

UHMWPE composites reinforced with Bovine Bone Hydroxyapatite (BHA) in different contents were prepared by heat pressing formation method. A hip joint wear simulator was used to investigate the biotribological behavior of UHMWPE/BHA composite acetabular cups against CoCrMo alloy femoral heads in bovine synovia lubrication at 37 ±1 ?C. It was found that the addition of BHA powder to UHMWPE can improve the hardness and creep modulus of UHMWPE/BHA composites, and decrease their wear rates under bovine synovia lubrication. When the content of BHA filler particles was up to 30 wt%, UHMWPE/BHA composites demonstrated the well design performances of the surface and biotribological properties. Fatigue, ploughing and slight adhesive wear were the main wear mechanisms for UHMWPE and its composites. In addition, the sizes of wear particles became larger with an increase in BHA powder addition. These results suggest that BHA filler is a desirable component to increase the wear resistance of UHMWPE/BHA composites for biomedical applications.

Reliable computational foot models offer an alternative means to enhance knowledge on the biomechanics of human foot. Model validation is one of the most critical aspects of the entire foot modeling and analysis process. This paper presents an in vivo experiment combining motion capture system and plantar pressure measure platform to validate a three-dimensional finite element model of human foot. The Magnetic Resonance Imaging (MRI) slices for the foot modeling and the experimental data for validation were both collected from the same volunteer subject. The validated components included the comparison of static model predictions of plantar force, plantar pressure and foot surface deformation during six loading conditions, to equivalent measured data. During the whole experiment, foot surface deformation, plantar force and plantar pressure were recorded simultaneously during six different loaded standing conditions. The predictions of the current FE model were in good agreement with these experimental results.

In the present work, a parametric numerical study is conducted in order to assess the effect of airfoil cambering on the aerodynamic performance of rigid heaving airfoils. The incompressible Navier-Stokes equations are solved in their velocity-pressure formulation using a second-order accurate in space and time finite-difference scheme. To tackle the problem of moving boundaries, the governing equations are solved on overlapping structured grids. The numerical simulations are performed at a Reynolds number of Re = 1100 and at different values of Strouhal number and reduced frequency. The results obtained show that the airfoil cambering geometric parameter has a strong influence on the average lift coefficient, while it has a smaller impact on the average thrust coefficient and propulsive efficiency of heaving airfoils.

Unsteady aerodynamic characteristics of a seagull wing in level flight are investigated using a boundary element method. A new no-penetration boundary condition is imposed on the surface of the wing by considering its deformation. The geometry and kinematics of the seagull wing are reproduced using the functions and data in the previously published literature. The proposed method is validated by comparing the computed results with the published data in the literature. The unsteady aerodynamics characteristics of the seagull wing are investigated by changing flapping frequency and advance ratio. It is found that the peak values of aerodynamic coefficients increase with the flapping frequency. The thrust and drag generations are complicated functions of frequency and wing stroke motions. The lift is inversely proportional to the advance ratio. The effects of several flapping modes on the lift and induced drag (or thrust) generation are also investigated. Among three single modes (flapping, folding and lead & lag), flapping generates the largest lift and can produce thrust alone. For three combined modes, both flapping/folding and flapping/lead & lag can produce lift and thrust larger than the flapping-alone mode can. Folding is shown to increase thrust when combined with flapping, whereas lead & lag has an effect of increasing the lift when also combined with flapping. When three modes are combined together, the bird can obtain the largest lift among the investigated modes.  Even though the proposed method is limited to the inviscid flow assumption, it is believed that this method can be used to the design of flapping micro aerial vehicle.

Underwater robot is a new research field which is emerging quickly in recent years. Previous researches in this field focus on Remotely Operated Vehicles (ROVs), Autonomous Underwater Vehicles (AUVs), underwater manipulators, etc. Fish robot, which is a new type of underwater biomimetic robot, has attracted great attention because of its silence in moving and energy efficiency compared to conventional propeller-oriented propulsive mechanism.
However, most of researches on fish robots have been carried out via empirical or experimental approaches, not based on dynamic optimality. In this paper, we proposed an analytical optimization approach which can guarantee the maximum propulsive velocity of fish robot in the given parametric conditions. First, a dynamic model of 3-joint (4 links) carangiform fish robot is derived, using which the influences of parameters of input torque functions, such as amplitude, frequency and phase difference, on its velocity are investigated by simulation. Second, the maximum velocity of the fish robot is optimized by combining Genetic Algorithm (GA) and Hill Climbing Algorithm (HCA). GA is used to generate the initial optimal parameters of the input functions of the system. Then, the parameters are optimized again by HCA to ensure that the final set of parameters is the “near” global optimization. Finally, both simulations and primitive experiments are carried out to prove the feasibility of the proposed method.