Mike Hearn's initial wiki article for Micropayment channels is unidirectional, i.e. the payment can flow only from one party to another and not in the reverse direction.

Example 7, https://en.bitcoin.it/wiki/Contracts

Is there a protocol that allows micropayments to flow in both directions? The solution of creating 2 channels with Bitcoins locked up by both parties is obviously valid, and I am looking for something different.

Is there a way by which, only one party locks up bitcoins, opens up a channel with another party, and the micropayments can flow in both directions?