Just an example of a function that splits the input string into a set of substrings of a given length.

Split-Array.ps1

function Split-Array {
    [CmdletBinding()]
    param   (
        [Parameter()]
        [char[]]
        $InputObject,
        [Parameter()]
        [int]
        $PartSize
    )
    begin   {}
    process {
        for ($index = 0; $index -lt $InputObject.Count; $index += $PartSize) {
            [int]$arrayTail =   $InputObject.Count - $index
            [int]$buffSize  =   [System.Math]::Min($arrayTail,$PartSize)
            [char[]]$buffer =   [char[]]::new($buffSize)
            [array]::Copy($InputObject,$index,$buffer,0,$buffSize)
            [string]::new($buffer)
        }
    }
    end     {}
}

Split-Array -InputObject ([guid]::NewGuid().ToString('N').ToCharArray()) -PartSize 6