Precision positioning using a novel six axes compliant nano-manipulator

In this paper, a novel micro-scale nano-manipulator capable of positioning in six degrees of freedom (DOF) is introduced. Undesired deflections, while operating in a specific DOF, are restricted by the aid of distinctive design of flexure hinges and actuators’ arrangements. The compliant mechanism is actuated by thermo-electro-mechanical actuators, as they could be integrated and exert large forces in a nanometer resolution. The actuators are bidirectional capable of applying force in both transverse and longitudinal directions. Performance of the two degrees of freedom actuator is thoroughly explored via numerical and analytical analyses, showing a good agreement. The workspace and performance of the precision positioner is studied using finite element methods. Finally, identification of forward and inverse kinematic of the nano-manipulator is performed utilizing neural network concept. A well-trained and appropriate neural network can efficiently replace the time-consuming and complex analytical and experimental methods

Dynamic analysis and controller design for a slider–crank mechanism with piezoelectric actuators

AbstractDynamic behaviour of a slider–crank mechanism associated with a smart flexible connecting rod is investigated. Effect of various mechanisms’ parameters including crank length, flexibility of the connecting rod and the slider׳s mass on the dynamic behaviour is studied. Two control schemes are proposed for elastodynamic vibration suppression of the flexible connecting rod and also obtaining a constant angular velocity for the crank. The first scheme is based on feedback linearization approach and the second one is based on a sliding mode controller. The input signals are applied by an electric motor located at the crank ground joint, and two layers of piezoelectric film bonded to the top and bottom surfaces of the connecting rod. Both of the controllers successfully suppress the vibrations of the elastic linkage

Microfluidic encapsulation of cells in alginate particles via an improved internal gelation approach

An improved internal gelation approach is developed to encapsulate single mammalian cells in monodisperse alginate microbeads as small as 26μm in diameter and at rates of up to 1kHz with high cell viability. The cell damage resulting from contact with calcium carbonate nanoparticles as gelation reagents is eliminated by employing a co-flow microfluidic device, and the cell exposure to low pH is minimized by a chemically balanced off-chip gelation step. These modifications significantly improve the viability of cells encapsulated in gelled alginate particles. Two different mammalian cell types are encapsulated with viability of over 84%. The cells are functional and continue to grow inside the microparticles

Asymmetric speed modulation of a rotary blood pump affects ventricular unloading

OBJECTIVES Rotary blood pumps (RBPs) running at a constant speed are routinely used for the mechanical support of the heart in various clinical applications, from short-term use in heart-lung machines to long-term support of a failing heart. Their operating range is delineated by suction and regurgitation events, leaving limited control on the cardiac workload. This study investigates whether different ratios of systolic/diastolic support are advantageous over a constant-speed operation. METHODS In order to effectively control the load on the heart, this study aimed at developing a pulsatile control algorithm for rotary pumps to investigate the impact of pump speed modulation during systole and diastole on the left ventricle unloading. The CentriMagTM RBP with a modified controller was implanted in four sheep via a left thoracotomy and cannulated from the ventricular apex to the descending aorta. To modulate the pump speed synchronized with the heartbeat, custom-made real-time software detected the QRS complex of the electrocardiogram and controlled the pump speed during systole and diastole. Four different speed modulations with the same average speed but different systolic and diastolic speeds were compared with the baseline and the constant speed support. Left ventricular (LV) pressure and volume, coronary flow and pump flow were analysed to examine the influence of the pump speed modulation. RESULTS Pulsatile setting reduces the cardiac workload to 64% of the baseline and 72% of the constant speed value. Maximum unloading is obtained with the highest speed during diastole and high-pulse amplitude. End-diastolic volume in the pulsatile modes varied from 85 to 94% of the baseline and 96 to 107% of the constant speed value. Consequently, the mechanical load on the heart can be adjusted to provide assuagement, which may lead to myocardial recovery. The higher pump speed during systole results in an increase in the pulse pressure up to 140% compared with the constant speed. CONCLUSIONS The present study is an initial step to more accurate speed modulation of RBPs to optimize the cardiac load control. To develop future control algorithms, the concept of high speed during diastole having a maximal unloading effect on the LV and high speed during systole increasing the pulse pressure is worth considerin

Physiologic and hematologic concerns of rotary blood pumps: what needs to be improved?

Over the past few decades, advances in ventricular assist device (VAD) technology have provided a promising therapeutic strategy to treat heart failure patients. Despite the improved performance and encouraging clinical outcomes of the new generation of VADs based on rotary blood pumps (RBPs), their physiologic and hematologic effects are controversial. Currently, clinically available RBPs run at constant speed, which results in limited control over cardiac workload and introduces blood flow with reduced pulsatility into the circulation. In this review, we first provide an update on the new challenges of mechanical circulatory support using rotary pumps including blood trauma, increased non-surgical bleeding rate, limited cardiac unloading, vascular malformations, end-organ function, and aortic valve insufficiency. Since the non-physiologic flow characteristic of these devices is one of the main subjects of scientific debate in the literature, we next emphasize the latest research regarding the development of a pulsatile RBP. Finally, we offer an outlook for future research in the field

Asymmetric speed modulation of a rotary blood pump affects ventricular unloading

Rotary blood pumps (RBPs) running at a constant speed are routinely used for the mechanical support of the heart in various clinical applications, from short-term use in heart-lung machines to long-term support of a failing heart. Their operating range is delineated by suction and regurgitation events, leaving limited control on the cardiac workload. This study investigates whether different ratios of systolic/diastolic support are advantageous over a constant-speed operation

A droplet-based heterogeneous immunoassay for screening single cells secreting antigen-specific antibodies

High throughput heterogeneous immunoassays that screen antigen-specific antibody secreting cells are essential to accelerate monoclonal antibody discovery for therapeutic applications. Here, we introduce a heterogeneous single cell immunoassay based on alginate microparticles as permeable cell culture chambers. Using a microfluidic device, we encapsulated single antibody secreting cells in 35-40 mu m diameter alginate microbeads. We functionalized the alginate to capture the secreted antibodies inside the microparticles, enabling single cell analysis and preventing the crosstalk between the neighboring encapsulated cells. We demonstrated non-covalent functionalization of alginate microparticles by adding three secondary antibodies to the alginate solution to form high molecular weight complexes that become trapped in the porous nanostructure of alginate and capture the secreted antibodies. We screened anti-TNF-alpha antibody-secreting cells from a mixture of antibody-secreting cells

Microfluidic encapsulation of cells in alginate particles via an improved internal gelation approach

An improved internal gelation approach is developed to encapsulate single mammalian cells in monodisperse alginate microbeads as small as 26 mu m in diameter and at rates of up to 1 kHz with high cell viability. The cell damage resulting from contact with calcium carbonate nanoparticles as gelation reagents is eliminated by employing a co-flow microfluidic device, and the cell exposure to low pH is minimized by a chemically balanced off-chip gelation step. These modifications significantly improve the viability of cells encapsulated in gelled alginate particles. Two different mammalian cell types are encapsulated with viability of over 84 %. The cells are functional and continue to grow inside the microparticles

Physiologic and hematologic concerns of rotary blood pumps: what needs to be improved?

Over the past few decades, advances in ventricular assist device (VAD) technology have provided a promising therapeutic strategy to treat heart failure patients. Despite the improved performance and encouraging clinical outcomes of the new generation of VADs based on rotary blood pumps (RBPs), their physiologic and hematologic effects are controversial. Currently, clinically available RBPs run at constant speed, which results in limited control over cardiac workload and introduces blood flow with reduced pulsatility into the circulation. In this review, we first provide an update on the new challenges of mechanical circulatory support using rotary pumps including blood trauma, increased non-surgical bleeding rate, limited cardiac unloading, vascular malformations, end-organ function, and aortic valve insufficiency. Since the non-physiologic flow characteristic of these devices is one of the main subjects of scientific debate in the literature, we next emphasize the latest research regarding the development of a pulsatile RBP. Finally, we offer an outlook for future research in the field