enqueue styles for only mobile wp

I tried to enqueue some styles on mobile only using wp_is_mobile() function, but it always give me true, Here is the code (From functions.php file) :

    add_action('wp_enqueue_scripts','load_All_Styles'); // Set up styles

    function load_All_Styles() {
    wp_register_style('font-awesome',get_template_directory_uri().'/css/font-awesome.min.css',array(),false);
    wp_register_style('preloader',get_template_directory_uri().'/css/preloader.css',array(),false);
    wp_register_style('bootstrap',get_template_directory_uri().'/css/bootstrap.min.css',array(),false);

    if(wp_is_mobile()){
        wp_enqueue_style( 'font-awesome' );

    }
    if(is_front_page()) {
        wp_enqueue_style( 'preloader' );
    }
}

what method to use instead? Any Solutions?