Simultaneous oscillation and frequency tracking of multiple resonances via digitally implemented phase-locked loop array

1. A measurement system comprising:

one or more suspended microchannel resonators, each resonator comprising a fluid channel for flowing a carried substance therethrough;

an excitation element for driving the one or more resonators;

a sensor for monitoring motion of the one or more resonators;

at least one phase locked loop (PLL) in feedback between the excitation element and the sensor, wherein the PLL is configured to operate at or near a resonant mode of the one or more resonators; and

a processor for determining information from PLL internal signals indicative of a resonator frequency shift

wherein the system is configured to determine one or more properties of the carried substance on the one or more resonators by measuring the resonator frequency shift due to the presence of the carried substance as the carried substance flows through the fluidic channel on the one or more resonators, and

wherein the transfer function of the PLL is configurable for shape and bandwidth.

2. The system of claim 1 , further comprising fluidic control elements for flowing liquid and a cell through the fluid channel, wherein the carried substance is the cell.

3. The system of claim 2 , wherein the information determined from the resonant frequency shift includes a growth rate of the cell.

4. The system of claim 1 , wherein the processor determines a 1-dimensional mass distribution from a resonant frequency shift due the presence of the carried substance carried through the fluid channel on the resonator.

5. The system of claim 1 , wherein an array of resonators are operated together.

6. The system of claim 5 , wherein the array size is 10 or more resonators.

7. The system of claim 5 , wherein the resonant frequencies of the resonators are separated by at least 2 kHz.

8. The system of claim 5 , wherein the resonator frequency is between 30 kHz and 10 MHz.

9. The system of claim 5 , wherein the resonator dimensions range from 10 microns to 1000 microns in length and from 1 to 100 microns in cross section.

10. A method, the method comprising:

driving one or more resonators with an excitation element, each resonator comprising a fluid channel therethrough;

sensing motion of the one or more resonators with a sensor;

operating a phase locked loop (PLL), in feedback between the excitation element and the sensor, at or near a resonant mode of the resonator;

reading, by a processor, PLL internal signals indicative of a resonator frequency shift;

configuring a transfer function of the PLL for shape and bandwidth; and

determining a property of a carried substance from the resonator frequency shift due to the carried substance flowing in a liquid through the fluid channel of the resonator.

11. The method of claim 10 , wherein the determined property of the carried substance includes mass or a growth rate of the carried substance.

12. The method of claim 11 , wherein the carried substance is a mammalian cell.

13. The method of claim 10 , including determining a 1-dimensional mass distribution from a resonant shift due the presence of at least the carried substance on the resonator.

14. The method of claim 10 , wherein an array of resonators are operated together.

15. The method of claim 14 , wherein the array size is 10 or more resonators.

16. The method of claim 14 , wherein the resonant frequencies of the resonators are separated by at least 2 kHz.

17. The method of claim 14 , wherein the resonator frequency is between 30 kHz and 10 MHz.

18. The method of claim 14 , wherein the resonator dimensions range from 10 microns to 1000 microns in length and from 1 to 100 microns in cross section.

19. The system of claim 1 , wherein the PLL's are implemented in digital logic.

20. The system of claim 1 , wherein the PLL's are implemented on a Field Programmable Gate Array (FPGA).