A low power, microvalve regulated architecture for drug delivery systems

Optimization of Newtonian fluid pressure in microcantilever integrated flexible microfluidic channel for healthcare application

The demand for microfluidic pressure sensors is ever-increasing in various industries due to their crucial role in controlling fluid pressure within microchannels. While syringe pump setups have been traditionally used to regulate fluid pressure in microfluidic devices, they often result in larger setups that increase the cost of the device. To address this challenge and miniaturize the syringe pump setup, the researcher introduced integrated T-microcantilever-based microfluidic devices. In these devices, microcantilevers are incorporated, and their deflections correlate with the microchannel's pressure. When the relative pressure of fluid (plasma) changes, the T-microcantilever deflects, and the extent of this deflection provides information on fluid pressure within the microchannel. In this work, finite element method (FEM) based simulation was carried out to investigate the role of material, and geometric parameters of the cantilever, and the fluid viscosity on the pressure sensing capability of the T-microcantilever integrated microfluidic channel. The T-microcantilever achieves a maximum deflection of 127μm at a 5000μm/s velocity for Young's modulus(E) of 360 kPa of PDMS by employing a hinged structure. On the other hand, a minimum deflection of 4.05 × 10-5μm was attained at 5000μm/s for Young's modulus of 1 TPa for silicon. The maximum deflected angle of the T-cantilever is 20.46° for a 360 kPa Young's modulus while the minimum deflection angle of the T-cantilever is measured at 13.77° for 900 KPa at a fluid velocity of 5000μm s-1. The T-cantilever functions as a built-in microchannel that gauges the fluid pressure within the microchannel. The peak pressure, set at 8.86 Pa on the surface of the cantilever leads to a maximum deflection of 0.096μm (approximately 1μm) in the T-cantilever at a 1:1 velocity ratio. An optimized microfluidic device embedded with microchannels can optimize fluid pressure in a microchannel support cell separation.

Continuously Adjustable Micro Valve Based on a Piezoelectric Actuator for High-Precision Flow Rate Control

A MEMS-based micro valve fitted with a piezoelectric actuator is presented in order to achieve a continuously adjustable flow rate control. The micro valve is realized using a cost-effective fabrication scheme with simple polyimide (PI) bonding, which has an average shear strength of up to 39.8 MPa, indicating a relatively high reliability. The simulation results based on the finite element method (FEM) show that the valve membrane is able to seal the inlet and cut off the flow successfully with a piezoelectric force of 3N when the differential pressure is 200 kPa. The measurement of the flow rate through the outlets shows that the micro valve can control the flow rate effectively in a large range under different actuation voltages and differential pressures. When the actuation voltage is 140 V, the measured leak flow of the closed micro valve is smaller than 0.5 sccm with a differential pressure of 200 kPa.

A Peristaltic Micropump Based on the Fast Electrochemical Actuator: Design, Fabrication, and Preliminary Testing

Microfluidic devices providing an accurate delivery of fluids at required rates are of considerable interest, especially for the biomedical field. The progress is limited by the lack of micropumps, which are compact, have high performance, and are compatible with standard microfabrication. This paper describes a micropump based on a new driving principle. The pump contains three membrane actuators operating peristaltically. The actuators are driven by nanobubbles of hydrogen and oxygen, which are generated in the chamber by a series of short voltage pulses of alternating polarity applied to the electrodes. This process guaranties the response time of the actuators to be much shorter than that of any other electrochemical device. The main part of the pump has a size of about 3 mm, which is an order of magnitude smaller in comparison with conventional micropumps. The pump is fabricated in glass and silicon wafers using standard cleanroom processes. The channels are formed in SU-8 photoresist and the membrane is made of SiNx. The channels are sealed by two processes of bonding between SU-8 and SiNx. Functionality of the channels and membranes is demonstrated. A defect of electrodes related to the lift-off fabrication procedure did not allow a demonstration of the pumping process although a flow rate of 1.5 µL/min and dosage accuracy of 0.25 nL are expected. The working characteristics of the pump make it attractive for the use in portable drug delivery systems, but the fabrication technology must be improved.

Normally closed plunger-membrane microvalve self-actuated electrically using a shape memory alloy wire

Various microfluidic architectures designed for in vivo and point-of-care diagnostic applications require larger channels, autonomous actuation, and portability. In this paper, we present a normally closed microvalve design capable of fully autonomous actuation for wide diameter microchannels (tens to hundreds of μm). We fabricated the multilayer plunger-membrane valve architecture using the silicone elastomer, poly-dimethylsiloxane (PDMS) and optimized it to reduce the force required to open the valve. A 50-μm Nitinol (NiTi) shape memory alloy wire is incorporated into the device and can operate the valve when actuated with 100-mA current delivered from a 3-V supply. We characterized the valve for its actuation kinetics using an electrochemical assay and tested its reliability at 1.5-s cycle duration for 1 million cycles during which we observed no operational degradation.

A miniature, single use, skin-adhered, low-voltage, electroosmotic pumping-based subcutaneous infusion system

A programmable, skin-attached, 36 × 30 × 8 mm system for subcutaneous infusion of 1.2 mL of a drug solution is described. The system is intended to be replaced daily. It comprises a 20 × 14 × 8 mm electronic controller and power source, an 8 mm diameter 2 mm thick electroosmotic pump, a two-compartment reservoir for a pumped water and a drug solution, an adhesive tape for attachment to the skin, and a 6 mm long 27 gauge needle. Its removable electronic controller programs the dose rate and dose and is re-used. The electroosmotic pump consists of a porous ceramic membrane sandwiched between a pair of Ag/Ag2O plated carbon paper electrodes. It operates below 1.23 V, the thermodynamic threshold for water electrolysis without gassing. The flow rate can be adjusted between 4 and 30 μL min(-1) by setting either by the voltage (0.2-0.8 V) or the current (30-200 μA). For average flow rates below 4 μL min(-1), the pump is turned on and off intermittently. For example, a flow rate of 160 μL day(-1), i.e., 0.13 μL min(-1) for basal insulin infusion in type 1 diabetes management, is obtained when 10 s pulses of 75 μA is applied every 15 min. High flow rates of 10-30 μL min(-1), required for prandial insulin administration, are obtained when the pump operates at 50-200 μA. To prevent fouling by the drug, only pure water passes the pump; the water pushes a drop of oil, which, in turn, pushes the drug solution.

Micro- and nano-fabricated implantable drug-delivery systems

Implantable drug-delivery systems provide new means for achieving therapeutic drug concentrations over entire treatment durations in order to optimize drug action. This article focuses on new drug administration modalities achieved using implantable drug-delivery systems that are enabled by micro- and nano-fabrication technologies, and microfluidics. Recent advances in drug administration technologies are discussed and remaining challenges are highlighted.

Compact, power-efficient architectures using microvalves and microsensors, for intrathecal, insulin, and other drug delivery systems

This paper describes a valve-regulated architecture, for intrathecal, insulin and other drug delivery systems, that offers high performance and volume efficiency through the use of micromachined components. Multi-drug protocols can be accommodated by using a valve manifold to modulate and mix drug flows from individual reservoirs. A piezoelectrically-actuated silicon microvalve with embedded pressure sensors is used to regulate dosing by throttling flow from a mechanically-pressurized reservoir. A preliminary prototype system is demonstrated with two reservoirs, pressure sensors, and a control circuit board within a 130cm(3) metal casing. Different control modes of the programmable system have been evaluated to mimic clinical applications. Bolus and continuous flow deliveries have been demonstrated. A wide range of delivery rates can be achieved by adjusting the parameters of the manifold valves or reservoir springs. The capability to compensate for changes in delivery pressure has been experimentally verified. The pressure profiles can also be used to detect catheter occlusions and disconnects. The benefits of this architecture compared with alternative options are reviewed.

MEMS-enabled implantable drug infusion pumps for laboratory animal research, preclinical, and clinical applications

Innovation in implantable drug delivery devices is needed for novel pharmaceutical compounds such as certain biologics, gene therapy, and other small molecules that are not suitable for administration by oral, topical, or intravenous routes. This invasive dosing scheme seeks to directly bypass physiological barriers presented by the human body, release the appropriate drug amount at the site of treatment, and maintain the drug bioavailability for the required duration of administration to achieve drug efficacy. Advances in microtechnologies have led to novel MEMS-enabled implantable drug infusion pumps with unique performance and feature sets. In vivo demonstration of micropumps for laboratory animal research and preclinical studies include acute rapid radiolabeling, short-term delivery of nanomedicine for cancer treatment, and chronic ocular drug dosing. Investigation of MEMS actuators, valves, and other microstructures for on-demand dosing control may enable next generation implantable pumps with high performance within a miniaturized form factor for clinical applications.