Micro magnetic silicone elastomer membrane ... - Semantic Scholar
Sensors and Actuators A 89 (2001) 259±266
Micro magnetic silicone elastomer membrane actuator Melvin Khoo, Chang Liu* Microelectronics Laboratory, Micro Actuators, Sensors, and Systems (MASS) Group, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA Received 22 November 1999; accepted 30 November 2000
Abstract We present results of the design, fabrication, and testing of a microfabricated, membrane-type magnetic actuator. Magnetic pieces made of electroplated Permalloy (Ni80Fe20) are embedded in a thin ¯exible membrane made of silicone elastomer. When an external magnetic ®eld is applied, a torque generated on the magnetic pieces produces membrane displacement. Permalloy pieces that are 100-mm-wide, 870mm-long, and 22-mm-thick are strategically positioned in a 2-mm-square, 40-mm-thick polydimethylsiloxane (PDMS) membrane (Sylgard 184). This design, produced through numerical simulations, is optimized to realize large membrane displacements. Tests performed on this membrane actuator showed displacements >80 mm in the presence of a 2:85 105 A/m external magnetic ®eld. Larger displacements are possible with greater magnetization ®elds. This type of membrane actuator can be applied to the fabrication of tetherless micropumps for use in micro¯uidic systems. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Magnetic actuation; Permalloy; Membrane; Microactuator; Silicone rubber
1. Introduction Micro liquid handling systems [1] have been an area of increasing interest in the ®eld of MEMS during recent years. Micropumps and valves are critical components in such systems. Various actuation principles and structures have been employed in micropumps and valves [2±9], and membrane actuator is a device class that has found wide applications. The actuation principles that have been applied to membrane actuators include piezoelectric [2], electrostatic [3,4], thermopneumatic [5], electrochemical [6], bimetallic [7], shape memory alloy [8], and electromagnetic [9]. Membrane materials that have been reported so far include silicon [2±4,9], low-stress silicon nitride [6,10], silicone elastomer [5], and polyimide [8,11]. The achievable displacements are generally limited, typically on the order of a few mm to 10±20 mm, thus limiting the overall volume ¯ow rate of micro membrane pumps. The biasing of such actuators is relatively complex. For example, in the case of electrostatic and piezoelectric membrane actuators, large voltages on the order of several hundred volts need to be applied to enable actuation. A piezoelectric (PZT) actuator for a micropump discussed by Koch et al. [2] requires a 600V driving voltage. * Corresponding author. Tel.: 1-217-333-4051; fax: 1-217-333-2476. E-mail address: [email protected] (C. Liu).
To achieve larger de¯ections under low-voltage or lowpower bias, structured membranes such as microbellow actuators [10] and corrugated membranes [11] have been investigated. Yang et al. [10] demonstrated de¯ections >50 mm for their three-layer circular microbellows actuator (membrane diameter being 800 mm), compared to a 13-mm de¯ection for a ¯at membrane of the same size under a 20 psi pressure differential. Neagu et al. [6] compared pressure± de¯ection relationships for ¯at and corrugated silicon nitride membranes of the same dimensions. A 1:2 mm 1:2 mm membrane with 13 corrugation rings showed de¯ections >75 mm at 5.8 psi while a ¯at membrane with same area yielded a 15-mm de¯ection under the same pressure. However, structured membranes generally require a more involved fabrication process than that needed for ¯at membranes. Alternatively, organic materials such as silicone elastomer [5] and polyimide [8,11] can also be used to achieve larger de¯ections in ¯at membranes due to their low Young's modulus and high Poisson's ratio. Silicone elastomer is especially promising because of the extremely low stiffness and high tear tolerance. To our knowledge, a silicone elastomer thin-®lm membrane with thickness
Micro magnetic silicone elastomer membrane actuator Melvin Khoo, Chang Liu* Microelectronics Laboratory, Micro Actuators, Sensors, and Systems (MASS) Group, University of Illinois at Urbana-Champaign, 208 North Wright Street, Urbana, IL 61801, USA Received 22 November 1999; accepted 30 November 2000
Abstract We present results of the design, fabrication, and testing of a microfabricated, membrane-type magnetic actuator. Magnetic pieces made of electroplated Permalloy (Ni80Fe20) are embedded in a thin ¯exible membrane made of silicone elastomer. When an external magnetic ®eld is applied, a torque generated on the magnetic pieces produces membrane displacement. Permalloy pieces that are 100-mm-wide, 870mm-long, and 22-mm-thick are strategically positioned in a 2-mm-square, 40-mm-thick polydimethylsiloxane (PDMS) membrane (Sylgard 184). This design, produced through numerical simulations, is optimized to realize large membrane displacements. Tests performed on this membrane actuator showed displacements >80 mm in the presence of a 2:85 105 A/m external magnetic ®eld. Larger displacements are possible with greater magnetization ®elds. This type of membrane actuator can be applied to the fabrication of tetherless micropumps for use in micro¯uidic systems. # 2001 Elsevier Science B.V. All rights reserved. Keywords: Magnetic actuation; Permalloy; Membrane; Microactuator; Silicone rubber
1. Introduction Micro liquid handling systems [1] have been an area of increasing interest in the ®eld of MEMS during recent years. Micropumps and valves are critical components in such systems. Various actuation principles and structures have been employed in micropumps and valves [2±9], and membrane actuator is a device class that has found wide applications. The actuation principles that have been applied to membrane actuators include piezoelectric [2], electrostatic [3,4], thermopneumatic [5], electrochemical [6], bimetallic [7], shape memory alloy [8], and electromagnetic [9]. Membrane materials that have been reported so far include silicon [2±4,9], low-stress silicon nitride [6,10], silicone elastomer [5], and polyimide [8,11]. The achievable displacements are generally limited, typically on the order of a few mm to 10±20 mm, thus limiting the overall volume ¯ow rate of micro membrane pumps. The biasing of such actuators is relatively complex. For example, in the case of electrostatic and piezoelectric membrane actuators, large voltages on the order of several hundred volts need to be applied to enable actuation. A piezoelectric (PZT) actuator for a micropump discussed by Koch et al. [2] requires a 600V driving voltage. * Corresponding author. Tel.: 1-217-333-4051; fax: 1-217-333-2476. E-mail address: [email protected] (C. Liu).
To achieve larger de¯ections under low-voltage or lowpower bias, structured membranes such as microbellow actuators [10] and corrugated membranes [11] have been investigated. Yang et al. [10] demonstrated de¯ections >50 mm for their three-layer circular microbellows actuator (membrane diameter being 800 mm), compared to a 13-mm de¯ection for a ¯at membrane of the same size under a 20 psi pressure differential. Neagu et al. [6] compared pressure± de¯ection relationships for ¯at and corrugated silicon nitride membranes of the same dimensions. A 1:2 mm 1:2 mm membrane with 13 corrugation rings showed de¯ections >75 mm at 5.8 psi while a ¯at membrane with same area yielded a 15-mm de¯ection under the same pressure. However, structured membranes generally require a more involved fabrication process than that needed for ¯at membranes. Alternatively, organic materials such as silicone elastomer [5] and polyimide [8,11] can also be used to achieve larger de¯ections in ¯at membranes due to their low Young's modulus and high Poisson's ratio. Silicone elastomer is especially promising because of the extremely low stiffness and high tear tolerance. To our knowledge, a silicone elastomer thin-®lm membrane with thickness
