Deferred tax assets (liabilities) (Detail) (USD $)	Dec. 31, 2013	Dec. 31, 2012
Deferred tax asset:
Net operating loss carryforwards	$ 25,504,000	$ 27,926,000
Accrued expenses	49,000	21,000
Amortization of definite lived intangible assets	15,000	16,000
Non-qualified stock option compensation	69,000	248,000
Depreciation	123,000	121,000
Other	297,000	227,000
Patents	(114,000)	(158,000)
State net operating loss carryforwards, net of federal tax benefit	19,000	428,000
Research tax credit carryforwards	2,223,000	2,080,000
Total deferred tax assets	28,185,000	30,909,000
Valuation allowance	(28,185,000)	(30,909,000)
Net deferred tax assets	$ 0	$ 0