ngSticky.js

angular.module('ui')
    .directive('ngSticky', function($window) {
      return function($scope, element) {
        var  start,
             $win = element($window);

        $win.on('scroll', function() {

          var scroll = $win.scrollTop();

          start = start || element.offset().top;

          if (scroll > start) {
            element.addClass('stuck');
          } else {
            element.removeClass('stuck');  
          }
        });
        
        $win.on('resize', function recheckPositions() {
          element.width( element.parent().width() );
        });
        
      };
    });