A Resettable Keypad Lock with Visible Readout Based on Closed Bipolar Electrochemistry and Electrochromic Poly(3‐methylthiophene) Films

Abstract

A closed bipolar electrode (BPE) system was developed with electrochromic poly(3-methylthiophene) (PMT) films electropolymerized on the ITO/rGO electrode as one pole of BPE in the reporting reservoir and the bare ITO electrode as another pole of BPE in the analyte reservoir, in which rGO represents reduced graphene oxide. Under a suitable driving voltage (Vtot), the electrochemical reduction/oxidation of electroactive probes, such as H2O2/glutathione (Glu), in the analyte reservoir could induce the reversible color change of PMT films in the reporting reservoir between blue and red. Based on this, a keypad lock with H2O2 , Glu, and Vtot =-3.0 V as the three inputs and the color change of PMT films as the visible output was established. This system was easily operated and did not need to synthesize the complex compounds or DNA molecules. The security system was easy to reset and could be used repeatedly.

User Authorization at the Molecular Scale

“…The latter are macroscopic analytical devices that, similar to the way the olfactory system operates, can interact non‐specifically with a wide range of analytes and discriminate among them by creating a wide range of unique identification patterns . Hence, the main difference between 8 and the molecular keypad locks discussed before is that instead of generating a single digital output (0 or 1) for each code entry, it associates each password with a unique emission “signature” that enables it to authorize multiple users.…”

“…In recent years, an alternative, molecular approach, to securing information has emerged. Rather than authorizing electronic or biometric signals with electronic circuits on solid support, the molecular approach relies on molecular‐based devices that can respond to specific input sequences (i.e., chemical or optical passwords) in solution . The idea of creating such systems has emerged from the field of molecular logic gates .…”

Dual-electrochromic bipolar electrode-based universal platform for the construction of various visual advanced logic devices

“…By contrast, colorimetric logic platforms present visual outputs that are rapidly responsive, easy-to-read, and could be observed by the naked eye. To the best of our knowledge, although many basic colorimetric logic gates (for example, AND, 22 INHIBIT, 23,24 OR 23 ) have been developed, only few single-output colorimetric advanced logic devices have been reported (keypad locks 25,26 or some simple concatenated logic circuits 23,27 ). This result is mainly because it is difficult to integrate two separate visible signals, which is necessary for fabricating dual-output advanced logic devices, into one reaction system.…”

“…[28][29][30] Logic computation based on bipolar electrochemistry has attracted tremendous interest recently owing to its ease of construction, integration and control. 25,[31][32][33] Crooks pioneered the integration of logic circuits with a split BPE using electrochemiluminescence as an output signal in an open BPE system. 33 However, the utilization of the open BPE mode limited further applications due to the low current efficiency.…”

“…By comparison, closed BPEs with ultrahigh current efficiency and non-interfering reactions at the two poles separated by different reservoirs have become increasingly popular. [34][35][36] Liu et al 25 fabricated a visual keypad lock based on a closed mode single-electrochromic BPE, but the single-output platform could not efficiently meet the requirements of visual advanced or concatenated logic devices. To overcome these limitations, more than one colorimetric signal should be integrated into one closed BPE system.…”