Label-free sorting of soft microparticles using a bioinspired synthetic cilia array.

Isolating cells of interest from a heterogeneous population has been of critical importance in biological studies and clinical applications. In this study, a novel approach is proposed for utilizing an active ciliary system in microfluidic devices to separate particles based on their physical properties. In this approach, the bottom of the microchannel is covered with an equally spaced cilia array of various patterns which is actuated by an external stimuli. 3D simulations are carried out to study cilia-particle interaction and isolation dynamic in a microfluidic channel. It is observed that these elastic hair-like filaments can influence particle's trajectories differently depending on their biophysical properties. This modeling study utilizes immersed boundary method coupled with the lattice Boltzmann method. Soft particles and cilia are implemented through the spring connected network model and point-particle scheme, respectively. It is shown that cilia array with proper stimulation is able to continuously and non-destructively separate cells into subpopulations based on their size, shape, and stiffness. At the end, a design map for fabrication of a programmable microfluidic device capable of isolating various subpopulations of cells is developed. This biocompatible, label-free design can separate cells/soft microparticles with high throughput which can greatly complement existing separation technologies.

Short fiber reinforced 3d printed ceramic composite with shear induced alignment.

This paper accounts for utilization of shear induced alignment method during ceramic stereolithography. Lateral oscillation mechanism, combined with 3d printed wall pattern, was employed to generate necessary shear to align fiber in desired direction. First, semicircular channel pattern was printed to assess the effect of difference between wall direction and oscillation direction on the fiber alignment. Then, flexural strength of ceramic matrix was tested with nickel coated carbon fiber and ceramic fiber reinforcements. The results demonstrated that the shear induced alignment further improves the flexural strength compare to randomly distributed samples. Flexural strength of aligned samples with 1.0 wt% carbon fiber loading was improved by ~90% compared to randomly orientated samples and by ~333% compared to unreinforced samples. Finally, fracture surface morphology of the flexural strength test specimens was evaluated. The main fracture mechanism was observed as fiber pull-out.

Acoustic Patterning for 3D Embedded Electrically Conductive Wire in Stereolithography.

In this paper, we reported a new approach for particle assembly with acoustic tweezer during three-dimensional (3D) printing for the fabrication of embedded conductive wire with 3D structures. A hexagon shaped acoustic tweezer was incorporated with Digital Light Processing (DLP) based stereolithography (SLA) printer to pattern conductive lines via aligning and condensing conductive nanoparticles. The effect of filler content on electrical resistivity and pattern thickness were studied for copper, magnetite nanoparticles, and carbon nanofiber reinforced nanocomposite samples. The obtained data was later used to produce examples of conductive 3D microstructures and embedded electronic components by using the suggested method.

Shear induced alignment of short nanofibers in 3D printed polymer composites.

3D printing of composite materials offers an opportunity to combine the desired properties of composite materials with the flexibility of additive manufacturing in geometric shape and complexity. In this paper, the shear-induced alignment of aluminum oxide nanowires during stereolithography printing was utilized to fabricate a nanowire reinforced polymer composite. To align the fibers, a lateral oscillation mechanism was implemented and combined with wall pattern printing technique to generate shear flow in both vertical and horizontal directions. A series of specimens were fabricated for testing the composite material's tensile strength. The results showed that mechanical properties of the composite were improved by reinforcement of nanofibers through shear induced alignment. The improvement of tensile strength was approximately ∼28% by aligning the nanowires at 5 wt% (∼1.5% volume fraction) loading of aluminum oxide nanowires.

Characterization of nanoparticle binding dynamics in microcirculation using an adhesion probability function.

Quantitative understanding of nanoparticles transport and adhesion dynamic in microcirculation is very challenging due to complexity of fluid dynamics and imaging setup. In-vitro experiments within microfluidic channels showed the significant influence of shear rate, carrier size, particle-substrate chemistry and vessel geometry on particle deposition rate. However, there are few theoretical models that can accurately predict experimental results. We have developed a numerical model to predict nanoparticle transport and binding dynamics and verified with our previous in-vitro tests results. A binding probability function is used to simplify the carrier attachment and detachment processes. Our results showed that due to the complex dynamics of particle transport and adhesion mechanism, the correlation between binding probability and actual deposition rate is not linear. Using experimental data, it is shown that the binding probability of small particles changes slightly with shear rate whereas the chance of binding for big particles decreases exponentially with shear. Our particulate model also captured some phenomena that cannot be achieved by continuum approach such as accumulation of drug particles in close vicinity of vessel wall. In addition, the effects of channel geometry and antibody density on particle binding are discussed extensively. The results from our particulate approach agrees well with experimental data suggesting that it can be used as a simple, yet efficient predictive tool for studying drug carrier binding in microcirculation.