Laravel从数据库中获取时间戳

I can't seem to get the create_at timstamp from a eloquent model but this seems not to be the case for other columns e.g. id. Can someone help me with this problem?

Data tabel

The code

//getting the collection
$collection = Scan::findOneById($scan->id);

//getting the first object(There is only one)
$storedScan = $collection->first();

//Util to get the type and prints it to console
Utils::printType($storedScan->id);
Utils::printType($storedScan->create_at);

Output

Type: integer

Type: NULL

the database column is called created_at