Also, the oscillating motion creates a loud screeching noise which is unpleasant for lab workers. The performance of resonant piezo actuators degrades as the contact points weaken and wear down the ceramic strip. Drawbacks of this type of solution are their considerable transfer function non-linearity, which makes closing a stable servo loop difficult. Piezo fingers oscillate against a ceramic strip to create motion. Other piezo stage alternatives employ unlimited travel piezo actuators, sometimes known as resonant piezo actuators. Adding levers reduces axial stiffness, resulting in reduced servo bandwidth and a reduction in step and settle performance. By adding a mechanical lever component to the piezo actuator, travel can be increased to 400 – 500 nanometers.

Some piezo stage alternatives use lever amplification, a spring, and a flexure to scale up the travel distance. The focusing process takes longer and these solutions are more expensive because you are essentially purchasing two separate focusing systems. The first is a macro-level focusing typically using a screw driven stepper motor stage, followed by switching to the piezoelectric stage for the micro-level focusing. One solution to the piezo stage’s movement limitation problem is to approach focusing in two phases. There have been some attempts over the years to engineer new solutions which would solve some of the drawbacks of piezo stages and unseat the piezo stage’s dominance. Piezo controls are also costly and are frequently complex to operate.īecause the name piezoelectric stages has become synonymous with imaging stages, alternative solutions have had a difficult time gaining a foothold in the market. The stiffness of a system is referred to as bandwidth, and piezo stages with flexures are typically lower bandwidth compared to a stage using a linear motor or screw combined with a crossed roller bearing.Īnother drawback to piezo stages is that the advanced crystalline materials (PZT) used in piezoelectric motors are expensive to produce and frequently include lead and other potentially hazardous materials. Because of their movement limitations, piezo stages may have difficulty accommodating thicker samples such as tissue samples.Īlso, the XY stage motions or other vibration sources such as pumps and fans in the microscope or diagnostic instrument can impart off-axis forces on the flexure which results in instability of the piezo stage. The larger moves are necessary for avoiding objective collisions with the sample or for finding the optimal focusing plane due to sample variations. It moves very tiny amounts, very precisely however, the initial steps of focusing often requires larger movements. Typically, a piezo stage can only move 100 – 300 nanometers. The use of piezo and flexure-based stages for XYZ focusing in this situation has many drawbacks. To control the movement of the stage, modern piezo stages are fitted with a controller and position feedback device and manipulated via a computer interface.Ī typical mult-axis imaging application involves a piezo stage moving an objective vertically for focusing with a separate sample motion using an XY stage. The piezoelectric actuator is composed of a piezo motor (motion created by applying voltage inverse piezoelectric effect) plus mechanical elements which allow the movement of the stage. Thus, a piezo stage, or piezoelectric stage, is a surface which is controlled by a piezo motor. They could harness the resulting electricity to develop motors that could make very miniscule and precise incremental movements. When they released the pressure, the crystalline material would give off the charge. The word piezo comes from the Greek word “to squeeze or press.” In 1880, the Curies discovered that when they squeezed certain types of materials, especially crystals, the material gained an electric charge. Piezo is an abbreviation of piezoelectric.

To bring the material into focus, the stage is moved in very tiny increments with great precision.Įnter the “piezo” of the piezo stage. The material can be anything from human cell samples screened for abnormalities to industrial materials tested for quality. Actuator or stage refers to a surface that holds material for inspection by a microscope or other imaging technology.

Piezo actuator close up