The control of acidity drives the assembly of biopolymers that are essential for a wide range of applications. Its miniaturization can increase the speed and the possibilities of combinatorial throughput for their manipulation, similar to the way that the miniaturization of transistors allows logical operations in microelectronics with a high throughput. Here, we present a device containing multiplexed microreactors, each one enabling independent electrochemical control of acidity in ∼2.5 nL volumes, with a large acidity range from pH 3 to 7 and an accuracy of at least 0.4 pH units. The attained pH within each microreactor (with footprints of ∼0.3 mm 2 for each spot) was kept constant for long retention times (∼10 min) and over repeated cycles of >100. The acidity is driven by redox proton exchange reactions, which can be driven at different rates influencing the efficiency of the device in order to achieve more charge exchange (larger acidity range) or better reversibility. The achieved performance in acidity control, miniaturization, and the possibility to multiplex paves the way for the control of combinatorial chemistry through pH-and aciditycontrolled reactions.

Controlling locally produced acidity in miniaturized spaces is of high importance yielding to manage simultaneous chemical reactions. Here we present a platform that hosts miniaturized micro reactors, each one enabling...

Controlling locally produced acidity in miniaturized spaces is of high importance yielding to manage simultaneous chemical reactions. Here we present a platform that hosts miniaturized micro reactors, each one enabling electrochemical control of the acidity in ~nL volumes. We demonstrated the local control of chemical reactions with the deprotection of strong acid labile groups in a region of 150 μm of diameter of an upstanding glass using high proton concentrations (~10-1M) and the acidity contrasts between the cell region and the outside. We demonstrated an accurate control of the proton concentration in aqueous and organic solvents and the control of chemical reactions in organic electrolytes achieved with a sulfonated tetrafluoroethylene-based membrane, that isolates the acid generating electrodes from the reagents in the solution. The quantitative control of the acidity by the Faradaic currents was demonstrated by the calibration of carboxyfluorescein adjusted with external titrations, and with a tautomer transition occurring at pH 4.2. To the best of our knowledge, this platform shows the best control of acidity in the smallest volume reported so far.

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In this work, we show the control of acidity and chemical reactions in nanofluidic electrochemical reactors with water and organic solvents. We demonstrate the accurate control of the proton concentration using Faradaic cur-rents calibrated against carboxyfluorescein adjusted with external titrations, but also with a tautomer transition occurring at pH 4.2. We deployed our platform for the control of acidity with organic solvents using a modification of the electrodes with a sulfonated tetrafluoroethylene-based membrane, that isolates the acid generating electrodes from the reagents in the solution. This configuration al-lowed us to follow the acidity in the cell using the same carboxyfluorescein, observing no deterioration of the acid/base cycles, proving the effective isolation of the electrodes. Finally, due to the high proton concentration and the acidity contrast between the cell and the outside that can be achieved with our system, we performed the deprotection of acid labile groups in an upstanding glass in a region with 150 μm of diameter. To the best of our knowledge, this plat-form shows the best control of acidity in the smallest volume reported so far.