Micromachined comb drive for quantitative nanoindentation

1. A method of mapping a material sample, the method comprising:

providing a micro electromechanical transducer comprising:

a body;

a probe moveable relative to the body; and

a micromachined comb drive including a differential capacitive displacement sensor to provide a sensor output signal representative of a position of the probe the differential capacitive displacement sensor to include a plurality of sensing capacitors, each sensing capacitor comprising a plurality of comb capacitors and each configured to provide capacitance levels which, together, are representative of a position of the probe, wherein each of the comb capacitors includes a fixed electrode comb coupled to the body and a moveable electrode comb coupled to the probe, and wherein the capacitance levels are based on a gap between the fixed electrode comb and the moveable electrode comb;

scanning at least an area of the sample using the transducer to map at least a portion of the material sample; and

defining a tip coupled to the probe, and exciting the tip at a desired frequency and measuring the amplitude and phase response.

2. The method of claim 1 , wherein the probe includes an indenter tip.

3. The method of claim 1 , further comprising exciting the probe at a frequency 0.1 Hz or greater up to 10 kHz.

4. The method of claim 1 , further comprising:

recording data while scanning the area of the sample.

5. The method of claim 4 , further comprising using a DC probe-sample contact force as a control feedback.

6. The method of claim 4 , further comprising:

determining mechanical properties of the material using the recorded data.

7. The method of claim 6 , further comprising determining a storage modulus representative of elastic property of a sample.

8. The method of claim 6 , wherein recording data includes recording a topography, amplitude and phase data.

9. A method of mapping a material sample, the method comprising:

providing a micro electromechanical transducer comprising:

a body;

a probe moveable relative to the body; and

a micromachined comb drive including a differential capacitive displacement sensor to provide a sensor output signal representative of a position of the probe;

scanning at least an area of the sample using the transducer to map at least a portion of the material sample,

the micromachined comb drive further including an electrostatic actuator capacitor to move the probe and apply force on a sample; and

defining a tip coupled to the probe, and exciting the tip at a desired frequency and measuring the amplitude and phase response.

10. The method of claim 9 , including defining the electrostatic actuator capacitor to include a plurality of comb capacitors configured to drive the probe, along a displacement axis, upon application of a bias voltage to the actuator capacitor.

11. The method of claim 9 , including defining the differential capacitive displacement sensor to include a plurality of sensing capacitors, each sensing capacitor comprising a plurality of comb capacitors and each configured to provide capacitance levels which, together, are representative of a position of the probe, wherein each of the comb capacitors of the actuator capacitor and the sensing capacitors includes a fixed electrode comb coupled to the body and a moveable electrode comb coupled to the probe.

12. A method of mapping a material sample, the method comprising:

providing a microelectromechanical transducer comprising:

a body;

a probe moveable relative to the body;

a micromachined comb drive including a differential capacitive displacement sensor to provide a sensor output signal representative of a position of the probe the differential capacitive displacement sensor to include a plurality of sensing capacitors, each sensing capacitor comprising a plurality of comb capacitors and each configured to provide capacitance levels which, together, are representative of a position of the probe, wherein each of the comb capacitors includes a fixed electrode comb coupled to the body and a moveable electrode comb coupled to the probe, and wherein the capacitance levels are based on a gap between the fixed electrode comb and the moveable electrode comb; scanning at least an area of the sample using the transducer to map at least a portion of the material sample;

recording data while scanning the area of the sample;

determining mechanical properties of the material using the recorded data; and

wherein determining mechanical properties of the material includes using the recorded data and a shape of a tip coupled to the probe.

13. A method of mapping a material sample, the method comprising:

providing a microelectromechanical transducer comprising:

a body;

a probe moveable relative to the body;

a micromachined comb drive including a differential capacitive displacement sensor to provide a sensor output signal representative of a position of the probe the differential capacitive displacement sensor to include a plurality of sensing capacitors, each sensing capacitor comprising a plurality of comb capacitors and each configured to provide capacitance levels which, together, are representative of a position of the probe, wherein each of the comb capacitors includes a fixed electrode comb coupled to the body and a moveable electrode comb coupled to the probe, and wherein the capacitance levels are based on a gap between the fixed electrode comb and the moveable electrode comb; scanning at least an area of the sample using the transducer to map at least a portion of the material sample;

recording data while scanning the area of the sample; and

wherein recording data includes recording a topography, amplitude and phase data.

14. A method of mapping a material sample, the method comprising:

providing a micro electromechanical transducer comprising:

a body;

a probe moveable relative to the body; and

a micromachined comb drive including a differential capacitive displacement sensor to provide a sensor output signal representative of a position of the probe;

scanning at least an area of the sample using the transducer to map at least a portion of the material sample,

further comprising recording data while scanning the area of the sample, and

measuring amplitude and phase data using a lock-in amplifier.

15. A method of mechanical property mapping of a material sample, the method comprising:

providing a micro electromechanical transducer comprising:

a body;

a probe moveable relative to the body; and

a micromachined comb drive including:

an electrostatic actuator capacitor to move the probe and apply force on a sample; and

a differential capacitive displacement sensor to provide a sensor output signal representative of a position of the probe;

exciting the probe at a desired frequency and measuring the amplitude and phase response; and

topography image scanning at least an area of the sample using the transducer.

16. The method of claim 15 , further comprising:

recording data while topography image scanning the area of the sample; and determining mechanical properties of the material using the recorded data.

17. The method of claim 16 , wherein determining properties of the material includes using the recorded data and a shape of the tip.

18. The method of claim 16 , further comprising determining a storage modulus representative of elastic property of a sample.

19. The method of claim 16 , further comprising determining a loss modulus representative of dissipative mechanical property of a sample.

20. A method of performing a modulus mapping of a material sample, the method comprising:

using a microelectromechanical (MEMS) nanoindenter transducer comprising:

a body;

a probe moveable relative to the body;

an indenter tip coupled to an end of the moveable probe, the indenter tip moveable together with the probe; and

a micromachined comb drive including:

an electrostatic actuator capacitor comprising a plurality of comb capacitors configured to drive the probe, together with the indenter tip, along a displacement axis, including in an indentation direction, upon application of a bias voltage to the actuation capacitor; and

a plurality of sensing capacitors forming a differential capacitive displacement sensor, each sensing capacitor comprising a plurality of comb capacitors and each configured to provide capacitance levels which, together, are representative of a position of the probe, wherein each of the comb capacitors of the actuator capacitor and the sensing capacitors includes a fixed electrode comb coupled to the body and a moveable electrode comb coupled to the probe;

exciting the indenter tip at a desired frequency;

recording a topography, amplitude and phase data while scanning a specified area of the material sample using a DC probe-sample contact force as control feedback and a lock-in amplifier for amplitude phase response measurement.

21. The method of claim 20 , including determining mechanical properties of the material sample based on the recorded amplitude and phase data.