Fabrication and mathematical analysis of an electrochemical microactuator (ECM) using electrodes coated with platinum nano-particles

Abstract

This paper reports the design, fabrication, modeling, and analysis of an electrochemical microactuator (ECM). The driving mechanism of the ECM is based on the reversible electrolysis process of water. The expansion and shrinkage of gas bubbles generated in a micro electrochemical chamber during a reversible electrolysis process can be used for actuation in microfluidic systems. The fluidic components of the ECM were fabricated on a glass substrate using UV lithography of SU-8. Two electrodes were used, with one Pt black (coated with platinum nanoparticles) as working and auxiliary electrode and the other Ag/AgCl coated as reference. The nano particles coated on the working electrode help to boost the surfaceto-volume ratio of the electrode and to obtain higher operation frequency. Pulse electropotentials were supplied for active control of expansion and shrinkage of gas bubbles using reproducible electrochemical reactions. The theoretical volume change rate of gas bubbles was simulated as a function of time using the ideal gas law and compared with the measured volume change. The experimental results show the electrode coated with platinum nanoparticles helped to enhance the reversible electrolysis process significantly. The results also show that the dynamic model can be used to simulate the dynamic behaviors of the ECM actuator. The ECM can be used in microfluidic applications such as pumping or valves.

Transient nanobubbles in short-time electrolysis

“…Since then the process has been widely used in different applications including hydrogen production [3,4]. Nowadays electrolysis of water also finds applications in different kinds of microdevices such as actuators [5][6][7][8], pumps [9,10], and others [11,12]. Fast performance of microsystems requires processing on a short-time scale.…”

Analytical Modeling of Flowrate and Its Maxima in Electrochemical Bioelectronics with Drug Delivery Capabilities

“…The physics of wireless bioelectronics relying on electrochemistry as actuation method can be modeled approximately by the ideal gas law: where P is the pressure, V is volume change inside the electrolyte reservoir, V 0 is the initial volume of gas in the electrolyte reservoir, R is the ideal gas constant (8.3144 J mol −1 K −1 ), T is the temperature of the electrolyte, and n is the number of moles, which is linear to the electrical current i in the electrodes and is given by n = ((3 i )/(4 F )) t + n 0 following Nernst equation [ 35 ]. Here, t is time, F is Faraday's constant (96485 C mol −1 ), the ratio 3/4 corresponds to water and must be changed if using a different electrolyte according to the redox reaction [ 36 ], n 0 is the initial amount of gas moles in the electrolyte reservoir and is related to the initial volume of gas V 0 in the electrolyte reservoir [ 25 ] by P 0 V 0 = n 0 RT , and P 0 is the initial value of P , i.e., the initial environmental pressure at the target region (e.g., ~117 kPa when considering blood pressure).…”

High efficiency wireless electrochemical actuators: Design, fabrication and characterization by electrochemical impedance spectroscopy

“…where V experimental is the total volume of the generated hydrogen and oxygen gases and V theoretical is the theoretical volume of the generated gas bubbles [7]. V theoretical is calculated from:…”