N. Izadi

Fabrication of superficial neuromast inspired capacitive flow sensors

A fabrication process is presented which allows realizing the dense arrays of fully supported flexible SU-8 membranes with integrated electrodes underneath that support cylindrical hair-like structures on the top. Electrodes have been insulated from liquid to prevent short circuit or electrolysis. The process allows a controllable distance between counter electrodes. The excess squeeze film damping is eliminated with a closed membrane configuration with backside openings. A low-power differential capacitive measurement mechanism is employed as a sensor readout. These flow sensors provide a distributed sensing mechanism inspired by the superficial neuromast as found in the lateral line system of fish. This paper focuses on the fabrication of the sensors with preliminary mechanical results demonstrating the functionality of the fabricated devices.

Biomimetic Flow-Sensor Arrays Based on the Filiform Hairs on the Cerci of Crickets

In this paper we report on the latest developments in biomimetic flow-sensors based on the flow sensitive mechano-sensors of crickets. Crickets have one form of acoustic sensing evolved in the form of mechano receptive sensory hairs. These filiform hairs are highly perceptive to low-frequency sound with energy sensitivities close to thermal threshold. Arrays of artificial hair sensors have been fabricated using a surface micromachining technology to form suspended silicon nitride membranes and double-layer SU-8 processing to form 1 mm long hairs. Previously, we have shown that these hairs are sensitive to low-frequency sound, using a laser vibrometer setup to detect the movements of the nitride membranes. We have now realized readout electronics to detect the movements capacitively, using electrodes integrated on the membranes.

Adaptation for Frequency Focusing and Increased Sensitivity in Biomimetic Flow Sensors using Electrostatic Spring Softening

This paper presents the results of active adaptation of sensor sensitivity. By applying a DC-bias voltage to the sensing electrodes of a cricket inspired artificial hair sensor the effective spring stiffness can be adapted resulting in a reduced resonance frequency and increased sensitivity. An array of flow sensors was actuated using electrical and acoustical signals at different values of the DC-bias voltage. Characterization was done using a scanning laser vibrometer. Both resonance frequency versus applied DC-bias voltage and deflection-amplitude versus DC-bias voltage behave well in accordance to theory and show that adaptation by DC-biasing can be used for frequency focusing and increasing sensitivity.

Design and fabrication process for artificial lateral line sensors

In fish the lateral line is a sensory organ used to perceive water movement in the surrounding environment to localize prey or predators, to avoid obstacles, for schooling and more. The lateral line consists of many mechanoreceptors called neuromast which consist of groups of hair cells covered by a jelly-like cupula. There are two types of neuromasts: superficial neuromasts which are situated on the skin, and canal neuromasts which are located canals that are connected to the water outside of the fish through a series of pores. We review design aspects for MEMS fabrication of capacitive hair based flow sensor arrays opera¬ting in aquatic environments, biomimicking neuromasts. Exploiting information gained from nature building a system that allows the study of hydrodynamic mechanical interactions in complex noisy environments may help to uncover more about nature and how to make reliable artificial systems.