Displaying custom field for variant products

Hi
I have created a Product Custom Field.
I want to display the text inside the custom field when the customer selects a specific variant of a product.
For the main product this is done by placing this code in the layout:

<?php if(!empty($this->element->intro_txt)){
echo '<div id="intro_txt" class="border rounded bg-light p-3 my-3">'.$this->element->intro_txt.'</div>';
 }