Enhanced Luminescent Detection of Circulating Tumor Cells by a 3D Printed Immunomagnetic Concentrator

Circulating tumor cells (CTCs) are an indicator of metastatic progression and relapse. Since non-CTC cells such as red blood cells outnumber CTCs in the blood, the separation and enrichment of CTCs is key to improving their detection sensitivity. The ATP luminescence assay can measure intracellular ATP to detect cells quickly but has not yet been used for CTC detection in the blood because extracellular ATP in the blood, derived from non-CTCs, interferes with the measurement. Herein, we report on the improvement of the ATP luminescence assay for the detection of CTCs by separating and concentrating CTCs in the blood using a 3D printed immunomagnetic concentrator (3DPIC). Because of its high-aspect-ratio structure and resistance to high flow rates, 3DPIC allows cancer cells in 10 mL to be concentrated 100 times within minutes. This enables the ATP luminescence assay to detect as low as 10 cells in blood, thereby being about 10 times more sensitive than when commercial kits are used for CTC concentration. This is the first time that the ATP luminescence assay was used for the detection of cancer cells in blood. These results demonstrate the feasibility of 3DPIC as a concentrator to improve the detection limit of the ATP luminescence assay for the detection of CTCs.

Powder Filling and Sintering of 3D In-chip Solenoid Coils with High Aspect Ratio Structure

In this study, a 3D coil embedded in a silicon substrate including densely distributed through-silicon vias (TSVs) was fabricated via a rapid metal powder sintering process. The filling and sintering methods for microdevices were evaluated, and the effects of powder types were compared. The parameters influencing the properties and processing speed were analyzed. The results showed that the pre-alloyed powder exhibited the best uniformity and stability when the experiment used two or more types of powders to avoid the segregation effect. The smaller the particle diameter, the better the inductive performance will be. The entire structure can be sintered near the melting point of the alloy, and increasing the temperature increases strength, while resulting in low resistivity. Finally, an 800-µm-high coil was fabricated. This process does not need surface metallization and seed layer formation. The forming process involves only sintering instead of slowly growing copper with a tiny current. Therefore, this process has advantages, such as a process time of 7 h, corresponding to an 84% reduction compared to current electroplating processes (45 h), and a 543% efficiency improvement. Thus, this process is more efficient, controllable, stable, and suitable for mass production of devices with flexible dimensions.

Major-Axis Planning Method for Fabrication of High Aspect Ratio Structure Based on Two-Photon Photopolymerization Technology

The smallest forming unit in two-photon photopolymerization (TPP) micro-manufacturing technology is the voxel, the appearance of which resembles a spheroid. Traditional TPP micro-manufacturing is planned using the minor-axis dimension of a spheroid, which is smaller than its major-axis, thus, the spatial resolution can achieve submicron level. TPP can be used to manufacture microstructures with complex shapes. However, such fine spatial resolution inevitably lowers the overall manufacturing speed. For a microstructure with a height of hundred micrometers, the prolonged manufacturing time substantially increases the risk of manufacturing failure. Whereas typical methods use the minor-axis dimension for manufacturing planning, this study developed a novel major-axis planning (MAP) method that uses the longest dimension of the voxel. In this study, the MAP was realized in a 4-axis micro-manufacturing system (i.e., a rotation axis was added to the 3-axis motion stage). Specifically, a specially designed L-type glass substrate was first placed on the rotation axis and was rotated 90°, rendering the working plane parallel to laser beams. Subsequently, horizontal laser scanning was performed, during which the laser focus moved from the working plane horizontally, to polymerize a high-aspect-ratio structure. The commercial polymer OrmoComp was used with the MAP; only 10 s was required to fabricate a microstructure that had a height of 100 μm and an aspect ratio of 17. This study verified that TPP micro-manufacturing on a voxel’s major axis can fabricate microstructures. Moreover, the L-type glass substrate can be controlled programmably to rotate an L-type glass substrate for 4-axis TPP micro-manufacturing in the future.

Suppression of Frost Propagation With Micropillar Structure Engineered Surface

Despite that using surface-roughness-induced superhydrophobic surface as a solution for ice/snow accretion issues has achieved extensive progresses, its icephobicity breaks down in case of condensation frosting, while the high aspect ratio structure brings more concerns on its durability and sustainability. In this work we investigated condensate frosting on substrates fabricated with patterned micropillars having a small aspect ratio, and studied the freezing propagation with different pattern sizes. The results show that a coarse patterned substrate can effectively suppress the freeing propagation while a fine patterned one can drastically promote the freezing propagation. Frost coverage can also be reduced with proper pattern design. A theoretical model was developed to explain the mechanism of surface ice propagation, and agrees well in tendency with experiment measurements. The aim of this study is to provide some new insights on the influence of surface morphology on ice growth.

Comparative study of multilayered nanostructures for enhanced solar optical absorption

ABSTRACTImproved solar spectrum optical absorption in multilayered nanostructures consisting of metal, semiconductor and dielectric layers increase their potential for efficient photon to electron conversion. In this work, we analyze the influence of different nanostructure shapes and dimensions on the optical absorption in the vacuum wavelength range of 400 nm to 1500 nm based on Finite Domain Time Difference (FDTD) method. A periodic metallic photonic crystal composed of nanorods of gold, titanium oxide, and alumina is proposed by optimizing thickness of Au and TiO2, aspect ratio, sidewall angle, and geometry of the elemental shape. A high aspect ratio structure consisting of elliptical nose cone elements with optimized dimensions is seen to absorb more than 90% of the solar spectrum in the range considered.