Use the Split operator with an empty delimiter, then cut the first & last elements out:
PS C:\Users\Matth> $chars = ("Moët Wetwang 叉烧包" -split "") | Select -SkipLast 1 -Skip 1
PS C:\Users\Matth> $chars.Length
16
PS C:\Users\Matth> $chars[2]
ë
PS C:\Users\Matth> $chars[15]
包