3-D real-time ultrasound tracking of acoustically actuated swimming microdrone.

Maneuverable microswimmers/microdrones that navigate in hard-to-reach spaces inside human bodies hold a great potential for various biomedical applications. Acoustically actuated microswimmers have already demonstrated feasibility. However, for eventual translation of this technology, a robust 3-D tracking strategy for the microswimmer is particularly required.

A System to Track Stent Location in the Human Body by Fusing Magnetometer and Accelerometer Measurements.

This paper will introduce a simple locating system to track a stent when it is deployed into a human artery. The stent is proposed to achieve hemostasis for bleeding soldiers on the battlefield, where common surgical imaging equipment such as fluoroscopy systems are not available. In the application of interest, the stent must be guided to the right location to avoid serious complications.

Synovial joint-on-a-chip for modeling arthritis: progress, pitfalls, and potential.

Disorders of the synovial joint, such as osteoarthritis (OA) and rheumatoid arthritis (RA), afflict a substantial proportion of the global population. However, current clinical management has not been focused on fully restoring the native function of joints. Organ-on-chip (OoC), also called a microphysiological system, which typically accommodates multiple human cell-derived tissues/organs under physiological culture conditions, is an emerging platform that potentially overcomes the limitations of current models in developing therapeutics.

In vitro and In vivo assessment of a novel organ perfusion stent for successful flow separation in donation after cardiac death.

Shortage of healthy donors' organs has appeared as one of the main challenges for organ transplantation. This study focuses on the novel endovascular device development to increase the number of available organs from cardiac death donors. The primary objective of this study is the design validation of a newly developed stent graft for the abdominal organ perfusion with cardiac blood flow isolation.

PDMS-Zwitterionic Hybrid for Facile, Antifouling Microfluidic Device Fabrication.

Poly(dimethylsiloxane) (PDMS) has been used in a wide range of biomedical devices and medical research due to its biostability, cytocompatibility, gas permeability, and optical properties. Yet, some properties of PDMS create critical limitations, particularly fouling through protein and cell adhesion. In this study, a diallyl-terminated sulfobetaine (SB-diallyl) molecule was synthesized and then directly mixed with a commercial PDMS base (Sylgard 184) and curing agent to produce a zwitterionic group-bearing PDMS (PDMS-SB) hybrid that does not require a complex or an additional surface modification process for the desired end product.

Dielectrowetting Control of Capillary Force (Cheerios Effect) between Floating Objects and Wall for Dielectric Fluid.

A capillary interaction between floating objects and adjacent walls, which is known as "Cheerios effect", is a common phenomenon that generates capillary attraction or repulsion forces between them depending on their wettabilities, densities, geometries, and so on. This paper deals with controlling the capillary forces, specifically, acting on objects floating on a dielectric (non-conductive) fluid. A key control input parameter is the wettability (contact angle) of the sidewall adjacent to the floating object.

Breath Acetone Sensing Based on Single-Walled Carbon Nanotube-Titanium Dioxide Hybrids Enabled by a Custom-Built Dehumidifier.

Acetone is a metabolic byproduct found in the exhaled breath and can be measured to monitor the metabolic degree of ketosis. In this state, the body uses free fatty acids as its main source of fuel because there is limited access to glucose. Monitoring ketosis is important for type I diabetes patients to prevent ketoacidosis, a potentially fatal condition, and individuals adjusting to a low-carbohydrate diet.

3-D swimming microdrone powered by acoustic bubbles.

Mobile microrobots that maneuver in liquid environments and navigate inside the human body have drawn a great interest due to their possibility for medical uses serving as an in vivo cargo. For this system, the effective self-propelling method, which should be powered wirelessly and controllable in 3-D space, is of paramount importance. This article describes a bubble-powered swimming microdrone that can navigate in 3-D space in a controlled manner.

A biostable, anti-fouling zwitterionic polyurethane-urea based on PDMS for use in blood-contacting medical devices.

Polydimethylsiloxane (PDMS) is commonly used in medical devices because it is non-toxic and stable against oxidative stress. Relatively high blood platelet adhesion and the need for chemical crosslinking through curing, however, limit its utility. In this research, a biostable PDMS-based polyurethane-urea bearing zwitterion sulfobetaine (PDMS-SB-UU) was synthesized for potential use in the fabrication or coating of blood-contacting devices, such as a conduits, artificial lungs, and microfluidic devices.

A three-tier Rescue stent improves outcomes over balloon occlusion in a porcine model of noncompressible hemorrhage.

Background: Noncompressible hemorrhage remains a high-mortality injury, and aortic balloon occlusion poses limitations in terms of distal ischemic injury. Our hypothesis was that a retrievable Rescue stent would confer improved outcome over aortic balloon occlusion.

Methods: A three-tier, retrievable stent graft was laser welded from nitinol and polytetrafluoroethylene to provide rapid thoracic and abdominal coverage with an interval bare metal segment to preserve visceral flow.

Antifouling digital microfluidics using lubricant infused porous film.

Electrowetting-driven digital (droplet-based) microfluidics has a tremendous impact on lab-on-a-chip applications. However, the biofouling problem impedes the real applications of such digital microfluidics. Here we report antifouling digital microfluidics by introducing lubricant infused porous film to electrowetting (more exactly, electrowetting on dielectric or EWOD).

Ultrasound Tracking of the Acoustically Actuated Microswimmer.

Objective: The purpose of this paper is to demonstrate the ultrasound tracking strategy for the acoustically actuated bubble-based microswimmer.

Methods: The ultrasound tracking performance is evaluated by comparing the tracking results with the camera tracking. A benchtop experiment is conducted to capture the motion of two types of microswimmers by synchronized ultrasound and camera systems.

A novel customizable stent graft that contains a stretchable ePTFE with a laser-welded nitinol stent.

Customizable medical devices have recently attracted attentions both in dental and orthopedic device fields, which can tailor to the patients' anatomy to reduce the length of surgery time and to improve the clinical outcomes. However, development of the patient specific endovascular device still remains challenging due to the limitations in current 3D printing technology, specifically for the stent grafts. Therefore, our group has investigated the feasibility of a highly stretchable expanded-polytetrafluoroethylene (ePTFE) tube as a customizable graft material with the laser-welded nitinol backbone.

Damage control of caval injuries in a porcine model using a retrievable Rescue stent.

Objective: Early hemorrhage control before the operating room is essential to reduce the significant mortality associated with traumatic injuries of the vena cava. Conventional approaches present logistical challenges on the battlefield or in the trauma bay. A retrievable stent graft would allow rapid hemorrhage control in the preoperative setting when endovascular expertise is not immediately available and without committing a patient to the limitations of current permanent stents.

Precision Measurement of Phonon-Polaritonic Near-Field Energy Transfer between Macroscale Planar Structures Under Large Thermal Gradients.

Despite its strong potentials in emerging energy applications, near-field thermal radiation between large planar structures has not been fully explored in experiments. Particularly, it is extremely challenging to control a subwavelength gap distance with good parallelism under large thermal gradients. This article reports the precision measurement of near-field radiative energy transfer between two macroscale single-crystalline quartz plates that support surface phonon polaritons.

A Review of PMMA Bone Cement and Intra-Cardiac Embolism.

Percutaneous vertebroplasty procedure is of major importance, given the significantly increasing aging population and the higher number of orthopedic procedures related to vertebral compression fractures. Vertebroplasty is a complex technique involving the injection of polymethylmethacrylate (PMMA) into the compressed vertebral body for mechanical stabilization of the fracture. Our understanding and ability to modify these mechanisms through alterations in cement material is rapidly evolving.

A retrievable rescue stent graft and radiofrequency positioning for rapid control of noncompressible hemorrhage.

Background: Noncompressible hemorrhage of the torso remains a challenging surgical dilemma. Stent graft repair requires endovascular expertise, imaging, and inventory that are not available within the critical window of massive hemorrhage. We developed a retrievable stent graft for rapid hemorrhage.

Dielectrowetting manipulation for digital microfluidics: creating, transporting, splitting, and merging of droplets.

Generating, splitting, transporting, and merging droplets are fundamental and critical unit operations for digital (droplet-based) microfluidics. State-of-the-art digital microfluidics performs such operations commonly using electrowetting-on-dielectric (EWOD) in the typical configuration of two parallel channel plates. This paper presents such operations using dielectrowetting (derived from liquid dielectrophoresis), not EWOD, with an array of interdigitated electrodes.

A novel compartmentalised stent graft to isolate the perfusion of the abdominal organs.

Donation after cardiac death has been adopted to address the critical shortage of donor organs for transplant. Recovery of these organs is hindered by low blood flow that leads to permanent organ injury. We propose a novel approach to isolate the perfusion of the abdominal organs from the systemic malperfusion of the dying donor.

Dual chamber stent prevents organ malperfusion in a model of donation after cardiac death.

Background: The paradigm for donation after cardiac death subjects donor organs to ischemic injury. A dual-chamber organ perfusion stent would maintain organ perfusion without affecting natural cardiac death. A center lumen allows uninterrupted cardiac blood flow, while an external chamber delivers oxygenated blood to the visceral vessels.

2-D steering and propelling of acoustic bubble-powered microswimmers.

This paper describes bi-directional (linear and rotational) propelling and 2-D steering of acoustic bubble-powered microswimmers that are achieved in a centimeter-scale pool (beyond chip level scale). The core structure of a microswimmer is a microtube with one end open in which a gaseous bubble is trapped. The swimmer is propelled by microstreaming flows that are generated when the trapped bubble is oscillated by an external acoustic wave.

Cheerios Effect Controlled by Electrowetting.

The Cheerios effect is a common phenomenon in which small floating objects are either attracted or repelled by the sidewall due to capillary interaction. This attractive or repulsive behavior is highly dependent on the slope angles (angles of the interface on the wall or floating object with respect to a horizontal line) that can be mainly controlled by the wettability of the wall and floating object and the density of the object. In this paper, electrowetting on dielectric (EWOD) is implemented to the wall or floating object in order to actively control the wettability and thus capillary interaction.

Micropropulsion by an acoustic bubble for navigating microfluidic spaces.

This paper describes an underwater micropropulsion principle where a gaseous bubble trapped in a suspended microchannel and oscillated by external acoustic excitation generates a propelling force. The propelling swimmer is designed and microfabricated from parylene on the microscale (the equivalent diameter of the cylindrical bubble is around 60 μm) using microphotolithography. The propulsion mechanism is studied and verified by computational fluid dynamics (CFD) simulations as well as experiments.

Inherent amplitude demodulation of an AC-EWOD (electrowetting on dielectric) droplet.

Recently, it has been shown that amplitude modulation (AM) in a wireless EWOD (electrowetting on dielectric) via magnetic induction facilitates the transmission of a low frequency message signal and then the oscillation of droplets at a low frequency. This process requires demodulation to recover the message signal from the high-frequency AM signal. As a key contribution, this paper theoretically and experimentally shows that the EWOD-actuated droplet has the inherent functionality of demodulation.