a device for passing a biopolymer molecule includes a nanochannel formed between a surface relief structure , a patterned layer forming sidewalls of the nanochannel and a sealing layer formed over the patterned layer to encapsulate the nanochannel . the surface relief structure includes a three - dimensionally rounded surface that reduces a channel dimension of the nanochannel at a portion of nanochannel and gradually increases the dimension along the nanochannel toward an opening position , which is configured to receive a biopolymer .