A compact integrated microfluidic oxygenator with high gas exchange efficiency and compatibility for long-lasting endothelialization.

We have developed and tested a novel microfluidic device for blood oxygenation, which exhibits a large surface area of gas exchange and can support long-term sustainable endothelialization of blood microcapillaries, enhancing its hemocompatibility for clinical applications. The architecture of the parallel stacking of the trilayers is based on a central injection for blood and a lateral injection/output for gas which allows significant reduction in shear stress, promoting sustainable endothelialization since cells can be maintained viable for up to 2 weeks after initial seeding in the blood microchannel network. The circular design of curved blood capillaries allows covering a maximal surface area at 4 inch wafer scale, producing high oxygen uptake and carbon dioxide release in each single unit. Since the conventional bonding process based on oxygen plasma cannot be used for surface areas larger than several cm2, a new "wet bonding" process based on soft microprinting has been developed and patented. Using this new protocol, each 4 inch trilayer unit can be sealed without a collapsed membrane even at reduced 15 µm thickness and can support a high blood flow rate. The height of the blood channels has been optimized to reduce pressure drop and enhance gas exchange at a high volumetric blood flow rate up to 15 ml min-1. The simplicity of connecting different units in the stacked architecture is demonstrated for 3- or 5-unit stacked devices that exhibit remarkable performance with low primary volume, high oxygen uptake and carbon dioxide release and high flow rate of up to 80 ml min-1.

The Rotation of Microrobot Simplifies 3D Control Inside Microchannels.

This paper focuses on the control of rotating helical microrobots inside microchannels. We first use a 50 µm long and 5 µm in diameter helical robot to prove that the proximity of the channel walls create a perpendicular force on the robot. This force makes the robot orbit around the channel center line. We also demonstrate experimentally that this phenomenon simplifies the robot control by guiding it on a channel even if the robot propulsion is not perfectly aligned with the channel direction. We then use numerical simulations, validated by real experimental cases, to show different implications on the microrobot control of this orbiting phenomenon. First, the robot can be centered in 3D inside an in-plane microchannel only by controlling its horizontal direction (yaw angle). This means that a rotating microrobot can be precisely controlled along the center of a microfluidic channel only by using a standard 2D microscopy technology. Second, the robot horizontal (yaw) and vertical (pitch) directions can be controlled to follow a 3D evolving channel only with a 2D feedback. We believe this could lead to simplify imaging systems for the potential in vivo integration of such microrobots.

On-chip Microfluidic Multimodal Swimmer toward 3D Navigation.

Mobile microrobots have a promising future in various applications. These include targeted drug delivery, local measurement, biopsy or microassembly. Studying mobile microrobots inside microfluidics is an essential step towards such applications. But in this environment that was not designed for the robot, integration process and propulsion robustness still pose technological challenges. In this paper, we present a helical microrobot with three different motions, designed to achieve these goals. These motions are rolling, spintop motion and swimming. Through these multiple motions, microrobots are able to selectively integrate a chip through a microfluidic channel. This enables them to perform propulsion characterizations, 3D (Three Dimensional) maneuverability, particle cargo transport manipulation and exit from the chip. The microrobot selective integration inside microfluidics could lead to various in-vitro biologic or in-vivo biomedical applications.

A tuning fork based wide range mechanical characterization tool with nanorobotic manipulators inside a scanning electron microscope.

This study proposes a tuning fork probe based nanomanipulation robotic system for mechanical characterization of ultraflexible nanostructures under scanning electron microscope. The force gradient is measured via the frequency modulation of a quartz tuning fork and two nanomanipulators are used for manipulation of the nanostructures. Two techniques are proposed for attaching the nanostructure to the tip of the tuning fork probe. The first technique involves gluing the nanostructure for full range characterization whereas the second technique uses van der Waals and electrostatic forces in order to avoid destroying the nanostructure. Helical nanobelts (HNB) are proposed for the demonstration of the setup. The nonlinear stiffness behavior of HNBs during their full range tensile studies is clearly revealed for the first time. Using the first technique, this was between 0.009 N/m for rest position and 0.297 N/m before breaking of the HNB with a resolution of 0.0031 N/m. For the second experiment, this was between 0.014 N/m for rest position and 0.378 N/m before detaching of the HNB with a resolution of 0.0006 N/m. This shows the wide range sensing of the system for potential applications in mechanical property characterization of ultraflexible nanostructures.

Piezoresistive InGaAs/GaAs nanosprings with metal connectors.

This paper presents the fabrication, assembly, and characterization of piezoresistive nanosprings for creating nanoelectromechanical systems. The fabrication process is based on conventional microfabrication techniques to create a planar pattern in a 27nm thick, n-type InGaAs/GaAs bilayer that self-forms into three-dimensional structures during a wet etch release. As the nanosprings have lower doped thin and flexible layers, small metal pads have been attached to both sides for achieving stable ohmic contact with electrodes. Nanorobotic manipulation is applied to assemble the nanosprings between electrodes using electron-beam-induced deposition inside a scanning electron microscope, and the bridged nanosprings were then characterized for electromechanical properties. With their strong piezoresistive response, low stiffness, large-displacement capability, and excellent fatigue resistance, they are well-suited to function as sensing elements in high-resolution, large-range electromechanical sensors.