The typical base material for piezoelectric actuators is a class of ceramics called PZT, which are brittle in their raw form.

This bending motion is the strength, and in this case also called deflection or displacement, represented as ∆Xout in Figure 1, which corresponds to the amount of force produced by the actuator, Fout. When a voltage signal is applied, the beam bends, creating significant motion at the tip of the beam – hence the term bender. These actuators consist of two pieces of piezoelectric material mounted in a cantilever beam configuration (think: diving board). For more information on stack type actuators, check out TDK. Both types produce motion in a single axis, but benders have much more displacement. For haptics, the most common configurations piezoelectrics are the bender and the stack. In contrast, piezoelectric actuators generate motion through the piezoelectric effect, a property that causes the material to squeeze or stretch when an electric signal is applied. ERM actuators produce motion across two axes, whereas LRA actuators create motion in a single axis. These are the same type of actuators used in electric motors and speaker voice-coils that are common in modern appliances. To get a good feel for their performance, it helps to understand the qualitative differences between these actuators, so let’s look at how these actuators generate motion.ĮRM and LRA use magnetic properties to either spin a mass or push it up and down. Second is speed of the motion, measured as response time (in seconds) or frequency (in Hertz) for periodic signals. First is amplitude, which is the essentially the strength of motion and can be measured as acceleration (in g’s), force (in Newtons), or deflection (e.g. Performance is all about the motion that a tactor can produce, and for that there are two main criteria. There are a lot of quantitative criteria you can use to evaluate haptic actuators, but the most important is performance. We will look at the key performance parameters, the mechanisms behind the devices, and finally look at some examples of commercially available products. Here we will focus on tactile and vibrotactile feedback, which is felt in the skin, which is what these actuators are made for, but it is worth noting that the term haptics has come to encompass many other areas, like kinesthetic feedback felt by larger movements of limbs. These devices, also called tactors, short for “tactile actuators,' create motion that allow electronic devices to impart information to the user through their sense of touch. In this post, we discuss: the differences between piezo actuators, and the more traditional haptic actuators: eccentric rotating mass (ERM) motors, and linear resonant actuators (LRA). Here at, we have done a lot of research and development with piezoelectric (piezo for short) actuators to improve the hardware and open new avenues for haptic feedback. Haptic feedback has come a long way over the last few decades, from pagers to the iPhone’s taptic engine, but the hardware is still a limiting factor for the possibilities.

Piezo motor