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

Cheng, Chaojun; Nair, Ankitha Rajagopalan; Thakur, Raviraj; Fridman, Gene Y.

doi:10.1007/s10404-018-2049-1

Cited by 15 publications

(9 citation statements)

References 24 publications

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“…The valves are designed to be controlled on the PDMS chip using a shape memory alloy Nitinol muscle wire. The valves have been shown to operate for over 1 million cycles (Cheng et al, 2017, 2018; Fridman, 2017).…”

Section: Enabling Technologymentioning

confidence: 99%

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Aplin

Fridman

2019

Front. Neurosci.

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Implantable neuroprostheses such as cochlear implants, deep brain stimulators, spinal cord stimulators, and retinal implants use charge-balanced alternating current (AC) pulses to recover delivered charge and thus mitigate toxicity from electrochemical reactions occurring at the metal-tissue interface. At low pulse rates, these short duration pulses have the effect of evoking spikes in neural tissue in a phase-locked fashion. When the therapeutic goal is to suppress neural activity, implants typically work indirectly by delivering excitation to populations of neurons that then inhibit the target neurons, or by delivering very high pulse rates that suffer from a number of undesirable side effects. Direct current (DC) neural modulation is an alternative methodology that can directly modulate extracellular membrane potential. This neuromodulation paradigm can excite or inhibit neurons in a graded fashion while maintaining their stochastic firing patterns. DC can also sensitize or desensitize neurons to input. When applied to a population of neurons, DC can modulate synaptic connectivity. Because DC delivered to metal electrodes inherently violates safe charge injection criteria, its use has not been explored for practical applicability of DC-based neural implants. Recently, several new technologies and strategies have been proposed that address this safety criteria and deliver ionic-based direct current (iDC). This, along with the increased understanding of the mechanisms behind the transcutaneous DC-based modulation of neural targets, has caused a resurgence of interest in the interaction between iDC and neural tissue both in the central and the peripheral nervous system. In this review we assess the feasibility of in-vivo iDC delivery as a form of neural modulation. We present the current understanding of DC/neural interaction. We explore the different design methodologies and technologies that attempt to safely deliver iDC to neural tissue and assess the scope of application for direct current modulation as a form of neuroprosthetic treatment in disease. Finally, we examine the safety implications of long duration iDC delivery. We conclude that DC-based neural implants are a promising new modulation technology that could benefit from further chronic safety assessments and a better understanding of the basic biological and biophysical mechanisms that underpin DC-mediated neural modulation.

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Section: Enabling Technologymentioning

confidence: 99%

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Aplin

Fridman

2019

Front. Neurosci.

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“…Generally, poly(dimethylsiloxane) (PDMS) is the most commonly used membrane material due to its good optical transparency and high elasticity for large deformations [10]. Other materials, such as thermal plastic polymer [11,12], shape memory alloy [13,14], glass [15], and more are also used in certain situations. As for the deflection of the membrane, various mechanical [16,17], electrostatic [18,19], pneumatic [20,21], magnetic [22,23], piezoelectric [24], or thermal [25] mechanisms have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Microfluidic Passive Valve with Ultra-Low Threshold Pressure for High-Throughput Liquid Delivery

Zhang

Oseyemi

2019

Micromachines

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The microvalve for accurate flow control under low fluidic pressure is vital in cost-effective and miniaturized microfluidic devices. This paper proposes a novel microfluidic passive valve comprising of a liquid chamber, an elastic membrane, and an ellipsoidal control chamber, which actualizes a high flow rate control under an ultra-low threshold pressure. A prototype of the microvalve was fabricated by 3D printing and UV laser-cutting technologies and was tested under static and time-dependent pressure conditions. The prototype microvalve showed a nearly constant flow rate of 4.03 mL/min, with a variation of ~4.22% under the inlet liquid pressures varied from 6 kPa to 12 kPa. In addition, the microvalve could stabilize the flow rate of liquid under the time-varying sinusoidal pressures or the square wave pressures. To validate the functionality of the microvalve, the prototype microvalve was applied in a gas-driven flow system which employed an air blower or human mouth blowing as the low-cost gas source. The microvalve was demonstrated to successfully regulate the steady flow delivery in the system under the low driving pressures produced by the above gas sources. We believe that this new microfluidic passive valve will be suitable for controlling fluid flow in portable microfluidic devices or systems of wider applications.

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“…According to the working principle of a microfluidic valve, the reported valves can be classified as active type and passive type [9]. Active valves usually use external actuators such as pressurized gas [10,11,12], magnetic [13,14], electric [15,16], or thermal forces [17] to adjust the flow resistances of microchannels. As many actuators are highly sensitive, liquid can be controlled consciously and precisely, which enables the high compatibility of active valves in microfluidic large-scale integration [18,19,20].…”

Section: Introductionmentioning

confidence: 99%

Microfluidic Passive Flow Regulatory Device with an Integrated Check Valve for Enhanced Flow Control

Zhang

2019

Micromachines

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A passive microvalve has appealing advantages in cost-effective and miniaturized microfluidic applications. In this work, we present a passive flow regulatory device for enhanced flow control in a microfluidic environment. The device was integrated with two functional elements, including a flow regulating valve and a flow check valve. Importantly, the flow regulating valve could maintain a stable flow rate over a threshold liquid pressure, and the flow check valve enabled effective liquid on/off control, thus accurate forward flow without any backward leakage was achieved. The flow performance of the flow regulating valve was analyzed through 3D FSI (Fluid-Structure Interaction) simulation, and several key parameters (i.e., fluidic channel height and width, control channel length, and Young’s modulus) were found to influence valve flow rate directly. To examine the flow characteristics of the device, we fabricated a prototype using 3D printing and UV laser cutting technologies, and the flow rates of the prototype under varied test pressures were measured in forward and reverse modes, respectively. Experimental results showed that nearly a constant flow rate of 0.42 ± 0.02 mL s−1 was achieved in the forward mode at an inlet pressure range of 70 kPa to 130 kPa, and liquid flow was totally stopped in the reverse mode at a maximum pressure of 200 kPa. The proposed microfluidic flow regulatory device could be employed for accurate flow control in low-cost and portable Lab-on-a-Chip (LoC) applications.

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

Cited by 15 publications

References 24 publications

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Implantable Direct Current Neural Modulation: Theory, Feasibility, and Efficacy

Microfluidic Passive Valve with Ultra-Low Threshold Pressure for High-Throughput Liquid Delivery

Microfluidic Passive Flow Regulatory Device with an Integrated Check Valve for Enhanced Flow Control

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