The nanofibers are randomly attached to the glass substrate because they have different charges with glass substrate (attracting)
The nanofibers are oriented in an aligned structure because they have a similar charge to the glass substrate (repelling)
Apart from this, the nature of the nanofibers is also important. This means they might have just a physical attachment to the glass substrate, or you could employ a chemical process to attach them chemically, such as using a binding agent.