**1. Introduction**

Modern microfluidic applications are moving toward miniaturization and lowering current consumption demands. Consequently, digital system voltages are lowered to a level of 3 V and below, which are most commonly used today. On the other hand, piezoelectric micropumps need a high voltage signal in the range of few hundred volts for normal operation. Driving signal parameters are depending on PZT material (Lead zirconate titanate), construction and required performance of a specific micropump. Therefore, a low-power portable piezoelectric micropump driver presents an interesting challenge in electronics design.

In addition to being capable of high voltage waveform synthesis, the piezoelectric micropump driver should allow for the adaptations of signal waveform shape, amplitude and frequency. These parameters need to be optimized for a type of driven micropump in order to maximize the microfluidic system performance.

Commercially available drivers are often either physically large and therefore nonportable [1] or are dedicated to driving a particular type of piezoelectric micropump [2]. Furthermore, available drivers offer only limited signal flexibility. In our previous work, a 3-channel high voltage AB class linear amplifier was developed [3]. This module offered very good micropump driving signals up to 10 kHz, but it was not size optimized. A miniaturized, high-voltage micropump driver was also implemented using a piezo haptic driver DRV2667 [4]. This implementation featured fully-programmable signal shape, frequency and amplitude, but was limited by signal driving amplitude to 200 Vpp and frequency range up to 1 kHz. Current consumption was 134 mA at such high excitation voltages.

The above-listed limitations of referenced drivers encouraged the development of a simpler, cost-effective micropump driver electronic module, which would be limited to a rectangular driving signal, but would offer excitation with higher voltages, whilst maintaining the low-power aspect (i.e. current consumption in the order of tenths of mA). One option was to design the driver with a separate high-voltage power supply, which provides a driving signal using an H-bridge, but due to complexity of such a circuit, this never represented a cost-effective solution. H-bridge topology does not ground one of the micropump actuator terminals.

Low-cost aspect of aforementioned implementations was challenged by a transformerless design, proposed and patented by Fraunhofer IZM [5]. Their brilliantly simple idea features two switched-mode power supply (SMPS) boost converters, which operate in mutual exclusion. Each boost converter forms voltage of either positive/negative polarity, but both SMPS converters incorporate same piezoelectric micropump as its output capacitor. The need for a dedicated output capacitor results in a miniature, digitally controlled version of a piezoelectric micropump driving module. Such interchanging SMPS module design synthesizes rectangular shape of driving signal with resistor-capacitor (RC) charging and discharging transitions through the piezoelectric micropump. Though the resulting edge transitions of a rectangular micropump driving signal are not ideal, the performance of such a circuit can be considered adequate for certain cost- and size-sensitive applications. The primary objective of this chapter is to present the development of three distinctive micropump driving module designs with their impact on piezoelectric micropump electrical and fluidic characteristics.
