Systems and methods for self-limiting protein pore insertion in a membrane
Systems and methods for inserting a single pore into a membrane are described herein. A stepped or ramped voltage waveform can be applied across the membranes of the cells of an array, where the voltage waveform starts at first voltage and increases in magnitude over a period of time to a second voltage. The first voltage is selected to be low enough to reduce the risk of damaging the membrane, while the rate of voltage increase is selected to provide sufficient time for the pores to insert into the membranes. Once a pore is inserted into the membrane, the voltage across the membrane rapidly drops, thereby reducing the risk of damaging the membrane even if the applied voltage between the electrodes is further increased.
1. A method of forming an array of nanopore sensor cells, the method comprising:
introducing a nanopore proximate to a cell, the cell having a working electrode and a membrane sealing the cell, wherein the working electrode is powered by an electrically coupled power source;
applying a voltage waveform across the membrane of the cell, wherein the voltage waveform starts at first voltage and increases in magnitude over a period of time to a second voltage, wherein the voltage waveform comprises an AC modulation component, wherein the AC modulation component has an amplitude of less than 100 mV;
measuring an electrical measurement through the working electrode in response to the application of the AC modulation component while the voltage waveform is applied across the membrane of the cell; and
inserting the nanopore into the membrane during the step of applying the voltage waveform.
2. The method of claim 1 , wherein the first voltage is between 0 and 100 mV±10%, and the second voltage is between 100 to 2000 mV±10%.
3. The method of claim 1 , wherein the working electrode is a capacitive electrode.
4. The method of claim 1 , wherein the voltage waveform comprises a plurality of incremental steps between the first voltage and the second voltage.
5. The method of claim 4 , wherein the plurality of incremental steps are incremented by about 1 to 100 mV±10%.
6. The method of claim 4 , wherein the plurality of incremental steps are incremented by about 1 to 25 mV±10%.
7. The method of claim 4 , wherein each incremental step has a duration between 0.1 to 60 seconds±10%.
8. The method of claim 7 , wherein the duration of each of the incremental steps is varied.
9. The method of claim 7 , wherein the duration of the incremental steps at lower voltages is greater than the duration of the of incremental steps at the higher voltages.
10. The method of claim 7 , wherein the duration of each of the incremental steps is equal.
11. The method of claim 1 , wherein the voltage waveform comprises a ramp between the first voltage and the second voltage.
12. The method of claim 11 , wherein the ramp is between about 0.1 to 2.0 V per minute ±10%.
13. The method of claim 12 , wherein the ramp has a constant slope.
14. The method of claim 12 , wherein the ramp has a variable slope.
15. The method of claim 12 , wherein the ramp has a slope at lower voltages that is less than the slope at higher voltages.
16. The method of claim 1 , wherein the step of applying the voltage waveform is applied to an unthinned membrane.
17. The method of claim 16 , further comprising thinning the unthinned membrane with the applied voltage waveform.
18. The method of claim 1 , wherein the AC modulation component has a frequency between 10 Hz and 1000 Hz.