The Singapore company Tangem released bitcoin-bills, which the developers themselves call "smart banknotes."  However, they are not made of paper - in fact it is hardware cold wallets with an integrated S3D350A chip from Samsung.  At the same time, the novelty has common features with traditional banknotes.  So, each bitcoin-bill represents a certain fixed denomination in BTC and can be transferred physically for payment.  In the company itself Tangem development is called "uncoolable cold wallet."