Most refreshable Braille displays are constructed with pin-grid arrays like these:
Researchers at NIST have devised a solution that may be cheaper to make.
Could we make something even cheaper? Karen Erickson suggested a single disk with Braille characters embossed on the edge. This could be done using a manual label maker. Now all we have to do is quickly rotate the disk so that the correct character is on top where the user can feel it. It seems to me that a really cheap single character Braille display could be built this way. Little kids learning Braille could really benefit from such a thing.