![]() ![]() When operated in closed loop mode, an additional concern arises. While the use of a linear position feedback transducer and a closed loop servo control can overcome hysteresis and drift, compared to the inherent simplicity of an open loop voltage commanded piezo stack, this comes at a considerable added cost and complexity. The motion in the piezo actuator continues to slowly creep after a position step. This can be as much as 15% of full travel. Significant amount of hysteresis or variation of travel versus applied voltage between forward and reverse movement.A stack capable of 200 microns of motion (the most common upper limit among commercially available devices) will typically be about 200 mm long. The number of plates grows with increased travel, increasing both stack length and cost as travel increases. Typical piezo stages range in travel from 10 to 200 microns. Housed piezo actuators with internal preload springs are useful, but suffer from several limitations, including: These limitations can be significantly reduced if the stack is mounted within a housing and if powerful springs are used to produce a high internal preload. Piezo linear actuators by themselves, are fragile and unable to produce force in both directions. ![]() The voltage applied to the piezo stack is distributed to each of the plates within the stack in a parallel configuration.ĭepending on the nature of the piezo material (soft versus hard), the applied voltage range is typically either +/- 1000 volts for hard or high voltage stacks, or +/- 120 volts for soft or low voltage stacks. The ratio L/L (change in length to length) for an applied voltage is quite small for a single piezoceramic element, and so most actuators are composed of a large number of thin plates, referred to as a piezo stack. Today, the most common materials used for piezo linear actuators are either barium titanate or PZT (lead zirconate titanate) ceramics. Leslie DC, Easley CJ, Seker E, Karlinsey JM, Utz M et al (2009) Frequency-specific flow control in microfluidic circuits with passive elastomeric features.The inverse piezoelectric effect was first discovered by Pierre and Jacques Curie in 1881. Tovar AR, Patel MV, Lee AP (2011) Lateral air cavities for microfluidic pumping with the use of acoustic energy. Lab Chip 9:41–43Īhmed D, Mao X, Juluri BK, Huang TJ (2009) A fast microfluidic mixer based on acoustically driven sidewall-trapped microbubbles. Tovar AR, Lee AP (2009) Lateral cavity acoustic transducer. Microfluid Nanofluid 14:591–596Ĭhung SK, Cho SK (2008) On-chip manipulation of objects using mobile oscillating bubbles. Hashmi A, Heiman G, Yu G, Lewis M, Kwon H-J et al (2013) Oscillating bubbles in teardrop cavities for microflow control. Marmottant P, Hilgenfeldt S (2004) A bubble-driven microfluidic transport element for bioengineering. Marmottant P, Hilgenfeldt S (2003) Controlled vesicle deformation and lysis by single oscillating bubbles. Hashmi A, Yu G, Reilly-Collette M, Heiman G, Xu J (2012) Oscillating bubbles: a versatile tool for lab on a chip applications. Appl Phys Lett 102:023702Ĭoakley W, Nyborg WL (1978) Applications in ultrasound: its applications in medicine and biology. ![]() Xu Y, Hashmi A, Yu G, Lu X, Kwon H-J et al (2013) Microbubble array for on-chip worm processing. J Micromech Microeng 18:065020Ĭheung YN, Qiu H (2010) Acoustic microstreaming for droplet breakup in a microflow-focusing device. Xu J, Attinger D (2008) Drop on demand in a microfluidic chip. Gunther A, Jhunjhunwala M, Thalmann M, Schmidt MA, Jensen KF (2005) Micromixing of miscible liquids in segmented gas–liquid flow. Song H, Chen DL, Ismagilov RF (2006) Reactions in droplets in microfluidic channels. ![]()
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