Fruit Fly Flight Behavior Characterization Using MEMS Force Sensors

Introduction

The fruit fly (Drosophila melanogaster), shown in Figure 1, is a model organism studied by biologists for almost a century, and possesses a highly developed flight control system that provides the insect with the capability to perform robust stable flight, as well as exceedingly rapid and precise turning maneuvers. The neurophysiology and biomechanics are inextricably linked and must be considered at the systems level. Multimodal sensory input converges on only 18 control muscles [1] that are responsible for the fine-tuning of wing motion for maneuvering, the aerodynamic basis of which has recently been revealed [2]. Beyond its impressive flight behavior, the fact that Drosophila melanogaster is completely autonomous, extremely small, highly robust, and self replicating makes this organism particularly interesting from a microrobotics standpoint [3].

 Fruit Fly Flight Behavior Characterization Using MEMS Force Sensors
Figure1: <i>Drosophila melanogaster</i> in typical hovering posture.

To better understand the biomechanics underlying fly flight, precise measurements of the flight forces of these tiny (3mm long) insects must be obtained. MEMS technology provides the opportunity to develop much smaller and inexpensive microforce sensors with a high sensitivity and large bandwidth. Importantly, sensor mechanical properties are well-defined, allowing novel sensor designs to be implemented. Due to their small size, MEMS-based microforce sensors can be readily integrated into existing experimental setups and, therefore, provide a significantly enhanced data acquisition technology for biomechanical research.



Flight Force Measurement Using a Single Axis MEMS Force Sensor

Figure 2 shows a schematic and an SEM picture of a single axis MEMS force sensor [4]. A differential tri-plate comb drive is constructed by separating the two stationary comb sets (1) and (3) on either side of the movable comb set (2), which is suitable for production using bulk micromachining. Microfabrication is based on deep reactive ion etching (DRIE) on silicon on insulator (SOI) wafers. The sensor has a high sensitivity (1.35mV/µN), good linearity (<4%), and a large bandwidth (7.8kHz), and is therefore well suited for characterizing flight behavior of fruit flies.

Figure 2: MEMS force sensor schematic with differential tri-plate comb drives, the block diagram of sensor and readout circuitry, and an SEM picture of a microfabricated device.
Figure 2: MEMS force sensor schematic with differential tri-plate comb drives, the block diagram of sensor and readout circuitry, and an SEM picture of a microfabricated device.

Figure 3 shows a fruit fly tethered to the force sensor probe and the force sensor wire bonded to a PCB. The measured signal is periodic, with a fundamental frequency just above 200Hz, corresponding to the typical wing beat frequency of fruit flies. The measured instantaneous lift forces are as high as 35µN, as shown in Figure 4.

Figure 3: Flight force sensing of <i>Drosophila melanogaster</i> tethered to sensor probe.
Figure 3: Flight force sensing of Drosophila melanogaster tethered to sensor probe.

Figure 4: Flight forces from four flies over the duration of the time-normalized stroke cycle. The gray areas show 95% confidence intervals.
Figure 4: Flight forces from four flies over the duration of the time-normalized stroke cycle. The gray areas show 95% confidence intervals.

The fruit fly flight force measurement results demonstrate the effectiveness of this technique for reliable and precise real-time measurements of flight forces in tethered flying fruit flies, promising important technological advance for biomechanical studies.

Current Research Activities

Current research efforts focus on developing multi-axis MEMS force/torque sensors that are capable of measuring additional flight parameters, such as combined yaw, pitch, and roll moments and instantaneous thrust. Extending the single axis novel sensor design to multiple axes and integrating these MEMS sensors into a flight simulator control system will allow measurements to be made in unprecedented detail and provide further insight into flight biomechanics, which potentially offers guidance for microrobotic flying device design.

Group Members

References

  1. M.H. Dickinson and M.S. Tu, "The function of dipteran flight muscle," Comparative Biochemistry & Physiology, Vol. 116, No. 3, pp. 223-238, 1997.
  2. S.N. Fry, R. Sayaman, and M.H. Dickinson, "The aerodynamics of free-flight maneuvers in Drosophila," Science, Vol. 300, pp. 495-498, 2003.
  3. J. Yan, R. Wood, S. Avandhanula, M. Sitti, and R.S. Fearing, "Towards flapping wing control for a micromechanical flying insect," Proc. IEEE International Conference on Robotics and Automation (ICRA2001), Seoul, Korea, May 21-26, 2001, pp. 3901-3908.
  4. Yu Sun, D.P. Potassek, S.N. Fry, and B.J. Nelson, "Characterizing fruit fly flight behavior using a micro force sensor with a new comb drive configuration," Proc. IEEE International Conference on Micro Electro Mechanical Systems (MEMS2004), Maastricht, The Netherlands, Jan. 25-29, 2004, pp. 837-840.
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