Modeling and fabrication of electrostatically actuated diaphragms for on-chip valving of MEMS-compatible microfluidic systems

Abstract

This paper presents an analytical model to estimate the actuation potential of an electrostatic parylene-C diaphragm, processed on a glass wafer using standard microelectromechanical systems (MEMS) process technology, and integrable to polydimethylsiloxane (PDMS) based lab-on-a-chip systems to construct a normally-closed microvalve for flow manipulation. The accurate estimation of the pull-in voltage of the diaphragm is critical to preserve the feasibility of integration. Thus, we introduced an analytical model, in a good agreement with the finite element method (FEM), to extend the solution of the pull-in instability by including the effect of nonlinear stretching for multilayered circular diaphragms. We characterized the operation of fabricated diaphragms with a 300 µm radius for the parameters, including pull-in voltage (221 V on average), opening and closing response times (in microseconds), repeatability (more than 50 times), and touch area (25.3% ± 2.6% at pull-in potential). The experimental pull-in voltage shows close accuracy with the predicted results. Moreover, the diaphragm, sealed with a PDMS microchannel, was tested under fluid flow to prove the applicability of microfluidic integration. The hybrid fabrication method enables the realization of optically transparent and durable electrostatic microvalves for complex functioning of polymer-based microfluidic systems, as the extended analytical formulation permits accurate modeling of operation.

Experimental analysis of a low controlling voltage tri-electrode MEMS electrostatic actuator for array applications

“…For example, we can see in figure 17(a) that in the unipolar mode, the tested tri-actuator travels around 50 µm with only 0-26.6 V of controlling voltage. By contrast, in [31] an average of 0-221 V is required for closing and opening a microfluidic channel with a depth of not more than 9.1 µm. In [32], a controlling voltage of 0-128 V was used to control the electrostatic actuator with serpentine springs for a range of 9.89 µm.…”

“…One issue of this design is for having better leakage behavior, a thicker diaphragm is needed and as a result, a higher controlling voltage is required. This can be a serious problem as the regular pull-in voltage was as high as the average of 221 V [31]. Admassu et al built a parallel plate electrostatic microactuator with three spring-like x-beam configurations.…”

Electrostatic pull-in application in flexible devices: A review

“…Desai et al [ 75 ] and Patrascu et al [ 76 ] designed a microvalve based on PDMS with a pull-in voltage of 150 V and a pressure capacity of 23 kPa and a life cycle of 400 times. Atik et al [ 77 ] prepared a normally closed valve on glass substrates as shown in Figure 8 . The valve required an average voltage of 221 V, the response time was less than microseconds, and the lifecycles was more than 50 times.…”

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

“…For flow rate control, micro valves with a high response speed that are electrostatic driven, electromagnetic driven, and piezoelectric driven are the most commonly used active micro valves. As electromagnetic-driven micro valves suffer from large chip areas [9,10] and the electrostatic-driven micro valves typically operate in binary mode, which requires a relatively large valve array to control the flow [11][12][13], piezoelectric-driven micro valves are utilized in this work to achieve continuously adjustable and high-precision flow rate control. However, the piezoelectric-driven micro valves usually require a complex fabrication process [14][15][16].…”