<form action=“{{ site.url }}{{ site.baseurl }}search” method=“get”>

<div class="mdl-textfield mdl-js-textfield mdl-textfield--expandable">
  <label class="mdl-button mdl-js-button mdl-button--icon" for="search_box">
    <i class="material-icons">search</i>
  </label>
  <div class="mdl-textfield__expandable-holder">
    <input class="mdl-textfield__input" type="text" id="search_box" name="query">
    <label class="mdl-textfield__label" for="sample-expandable">Expandable Input</label>
  </div>
</div>

</form>