Piezoelectric devices are widely used in various applications, including pharmaceutical printing, for controlling droplet ejection. The principle behind piezoelectric droplet ejection is based on the piezoelectric effect, which is the ability of certain materials to generate an electric charge in response to applied mechanical stress or pressure. This effect is reversible, meaning that these materials can also change shape when an electric field is applied to them.
In pharmaceutical printing, piezoelectric devices are utilized to precisely control the ejection of tiny droplets of liquid, such as inks or pharmaceutical solutions, onto a substrate (such as a pill, tablet, or other pharmaceutical products) in a controlled and precise manner. Here's how it generally works:
Piezoelectric Actuator: A piezoelectric device typically consists of a piezoelectric material (such as lead zirconate titanate or PZT) that is integrated into an actuator mechanism. When a voltage is applied to the piezoelectric material, it undergoes a small change in shape, often on the order of micrometers. This change in shape can be harnessed to generate mechanical force.
Fluid Reservoir: The pharmaceutical solution or ink is held in a reservoir that is connected to a small nozzle or jet. The piezoelectric actuator is positioned near the nozzle.
Droplet Ejection: When a voltage pulse is applied to the piezoelectric actuator, it undergoes a rapid deformation or vibration. This deformation generates a mechanical pressure wave that travels through the fluid in the reservoir and reaches the nozzle. As a result, a tiny droplet of the fluid is forced out of the nozzle due to the sudden pressure change. The size of the droplet can be controlled by varying the amplitude and duration of the voltage pulse applied to the piezoelectric actuator.
Drop-on-Demand Printing: The ability to precisely control the ejection of droplets is crucial for drop-on-demand printing, where droplets are selectively ejected onto specific locations of a substrate to create patterns, text, or images. In pharmaceutical printing, this technology can be used to apply precise amounts of active pharmaceutical ingredients onto tablets or other pharmaceutical products.
Advantages of using piezoelectric droplet ejection in pharmaceutical printing include high precision, repeatability, and the ability to handle a wide range of fluids with varying viscosities. Additionally, since droplets are ejected only when needed, there is minimal waste of the pharmaceutical solution or ink.
It's important to note that there are other droplet ejection technologies as well, such as thermal inkjet printing, which uses heat to create vapor bubbles that expel droplets, and continuous inkjet printing, which generates a continuous stream of droplets, some of which are deflected and collected while others are not. Each technology has its own advantages and is chosen based on specific requirements of the application.