multiple selection input checkbox materialize does not work

<div class="row">
	<form action="#">
		<span>
			<?
			$sql = "SELECT * from $ufEstab where cidade = '{$cidadeEstab}' group by bairro";
			$query = mysqli_query($conexao,$sql);
			while ( $ln = mysqli_fetch_array($query)) {?>
				<div class="col s4">
					<input value="<?= utf8_encode($ln['bairro']);?>" type="checkbox" name="bairro" id="test5" />
					<label for="test5"><?= utf8_encode($ln['bairro']);?></label>
				</div>
			<? }//fim do while bairros ?>
		</span>
		<button class="btn">Cadastrar bairros</button>
	</form>
</div><!--row-->