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1. (WO2019063063) METHOD FOR INLINE BILAYER CAPACITANCE MONITORING
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CLAIMS

1. A method of detecting a state of a lipid membrane in a cell of a nanopore based sequencing chip, comprising:

coupling a lipid membrane with an integrating capacitor, wherein the lipid membrane is between a working electrode and a counter electrode;

applying an alternating current (AC) voltage to the counter electrode;

periodically sampling a voltage across the integrating capacitor by an analog-to-digital converter (ADC);

inserting an intermediate change in the AC voltage between two magnitudes of the AC voltage;

determining a change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage; and

detecting a state of the lipid membrane based on the determined change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage.

2. The method of claim 1, further comprising determining the change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage when the AC voltage is switching from a first phase to a second phase or when the AC voltage is switching from the second phase to the first phase, wherein a first phase magnitude of the AC voltage is greater than a second phase magnitude of the AC voltage.

3. The method of claim 2, further comprising determining the change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage when the AC voltage is switching from a first phase to a second phase or when the AC voltage is switching from the second phase to the first phase, and wherein the first phase comprises a positive square wave and the second phase comprises a negative square wave.

4. The method of claim 2, further comprising determining the change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage when the AC voltage is at an intermediate monitoring

magnitude, wherein the intermediate monitoring magnitude is smaller than the first phase magnitude but greater than the second phase magnitude.

5. The method of claim 4, further comprising selecting the intermediate monitoring magnitude based at least in part on a ADC reference window of the ADC.

6. The method of claim 4, further comprising:

comparing the change in the sampled voltage across the integrating capacitor against one or more predetermined thresholds, and

detecting the state of the lipid membrane based on the comparisons against the one or more predetermined thresholds, wherein the state of the lipid membrane is selected from the group consisting of: a lipid membrane with more than two lipid molecule layers, a lipid bilayer, and a ruptured lipid bilayer.

7. The method of claim 4, wherein the cell is one of a plurality of cells in a nanopore-based sequencing chip, and wherein the method further comprises:

pre-charging the integrating capacitor by connecting the integrating capacitor to a constant pre-charging voltage source using a global pre- charge signal, wherein the global pre-charge signal is used to control a timing of the pre-charging of integrating capacitors in the plurality of cells;

after the integrating capacitor is charged to the constant pre- charging voltage source value, disconnecting the pre-charging voltage source from the integrating capacitor using the global pre-charge signal, wherein the global pre-charge signal is used to control a timing of the disconnecting of the pre-charging voltage source from integrating capacitors in the plurality of cells;

waiting a predetermined period of time for the integrating capacitor to charge or discharge through a capacitance associated with the lipid bilayer; and

sampling the voltage across the integrating capacitor after the predetermined waiting period.

8. The method of claim 1, further comprising:

in response to the detection that the lipid bilayer has ruptured, disabling further electrical stimuli from being applied across the lipid bilayer by opening a switch in the cell.

9. A system or instrument for detecting a state of a lipid membrane in a cell of a nanopore based sequencing chip, comprising:

an integrating capacitor;

a working electrode coupled to the integrating capacitor;

a counter electrode, wherein a lipid membrane deposited between the working electrode and the counter electrode is coupled with the integrating capacitor;

an alternating current (AC) voltage source that applies an AC voltage to the counter electrode;

an analog-to-digital converter (ADC) periodically sampling a voltage across the integrating capacitor; and

a processor or a circuitry configured to:

insert an intermediate change in the AC voltage between two magnitudes of the AC voltage;

determine a change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage; and

detect a state of the lipid membrane based on the determined change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage.

10. The system or instrument of claim 9, wherein the processor or circuitry is further configured to:

determine the change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage when the AC voltage is switching from a first phase to a second phase or when the AC voltage is switching from the second phase to the first phase, wherein a first phase magnitude of the AC voltage is greater than a second phase magnitude of the AC voltage.

11. The system or instrument of claim 10, wherein the processor or circuitry is further configured to:

determine the change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage when the AC voltage is switching from a first phase to a second phase or when the AC voltage is switching from the second phase to the first phase, and wherein the first phase comprises a positive square wave and the second phase comprises a negative square wave.

12. The system or instrument of claim 10, wherein the processor or circuitry is further configured to:

determine the change in the sampled voltage across the integrating capacitor in response to the intermediate change in the AC voltage when the AC voltage is at an intermediate monitoring magnitude, wherein the intermediate monitoring magnitude is smaller than the first phase magnitude but greater than the second phase magnitude.

13. The system of claim 12, wherein the processor or circuitry is further configured to:

select the intermediate monitoring magnitude based at least in part on a

ADC reference window of the ADC.

14. The system or instrument of claim 12, wherein the processor or circuitry is further configured to:

compare the change in the sampled voltage across the integrating capacitor against one or more predetermined thresholds;

detect the state of the lipid membrane based on the comparisons against the one or more predetermined thresholds, wherein the state of the lipid membrane is selected from the group consisting of: a lipid membrane with more than two lipid molecule layers, a lipid bilayer, and a ruptured lipid bilayer.

15. The system or instrument of claim 12, wherein the cell is one of a plurality of cells in a nanopore-based sequencing chip, further comprising:

a constant pre-charging voltage source;

wherein the processor or circuitry is further configured to:

pre-charge the integrating capacitor by connecting the integrating capacitor to the constant pre-charging voltage source using a global pre- charge signal, wherein the global pre-charge signal is used to control a timing of the pre-charging of integrating capacitors in the plurality of cells;

after the integrating capacitor is charged to the constant pre- charging voltage source value, disconnect the pre-charging voltage source from the integrating capacitor using the global pre-charge signal, wherein the global pre-charge signal is used to control a timing of the disconnecting of the pre-charging voltage source from integrating capacitors in the plurality of cells;

wait a predetermined period of time for the integrating capacitor to charge or discharge through a capacitance associated with the lipid bilayer; and

cause the ADC to sample the voltage across the integrating capacitor after the predetermined waiting period.

The system or instrument of claim 12, further comprising:

a switch in the cell controlled by the processor or the circuitry;

wherein the processor or circuitry is further configured to:

in response to the detection that the lipid bilayer has ruptured, disable further electrical stimulus from being applied across the lipid bilayer by opening the switch in the cell.