Liquid metal-based bio-inspired capacitive flow sensor

We present a liquid flow sensor inspired by cupula structures found on a variety of fish. Our 5mm x 5mm x 1.75mm artificial cupula uniquely comprises a pair of differential liquid metal capacitors encased in silicone. Deflection of the structure – manually or by fluid flow – increases capacitance on one side and decreases on the other. To fabricate the complex internal structure, a commercial 3D printer is used to create a mold out of a sacrificial wax-like material. After casting uncured rubber, internal mold structures are melted and dissolved away, leaving channels and voids for liquid metal vacuum injection. The measured sensitivity of ~0.05pF/mm is compared to theoretical capacitance versus deflection values based on kinematics. To test behavior under water flow, a custom flow channel consisting of a 7.5mm x 7.5mm cross-section is employed with rates up to 1L/min. The parabolic capacitive response as a function of flowrate is compared to analytic theory based on kinematics and drag as well as to fluid-structure interaction (FSI) simulations using COMSOL. This device has future applications in the control of bio-inspired soft robotics. [Work sponsored by the Office of Naval Research.]

[1]  Michael Sfakiotakis,et al.  Review of fish swimming modes for aquatic locomotion , 1999 .

[2]  Jeffrey S. Moore,et al.  Robust sacrificial polymer templates for 3D interconnected microvasculature in fiber-reinforced composites , 2017 .

[3]  K. Kindt,et al.  Kinocilia mediate mechanosensitivity in developing zebrafish hair cells. , 2012, Developmental cell.

[4]  Gijsbertus J.M. Krijnen,et al.  Institute of Physics Publishing Journal of Micromechanics and Microengineering Artificial Sensory Hairs Based on the Flow Sensitive Receptor Hairs of Crickets , 2022 .

[5]  M. J. Wolfgang,et al.  Drag reduction in fish-like locomotion , 1999, Journal of Fluid Mechanics.

[6]  B.H. Calhoun,et al.  A capacitance-based whisker-like artificial sensor for fluid motion sensing , 2010, 2010 IEEE Sensors.

[7]  M. Dickey.  Stretchable and Soft Electronics using Liquid Metals , 2017, Advanced materials.

[8]  B. Gozen,et al.  Freeze‐Printing of Liquid Metal Alloys for Manufacturing of 3D, Conductive, and Flexible Networks , 2016 .

[9]  K. D. Karavitaki,et al.  From Biological Cilia to Artificial Flow Sensors: Biomimetic Soft Polymer Nanosensors with High Sensing Performance , 2016, Scientific Reports.

[10]  Peter Görner,et al.  Untersuchungen zur Morphologie und Elektrophysiologie des Seitenlinienorgans vom Krallenfrosch (Xenopus laevis Daudin) , 1963, Zeitschrift für vergleichende Physiologie.

[11]  A. Scherer,et al.  Replication of three-dimensional valves from printed wax molds , 2007 .

[12]  Carmel Majidi,et al.  3D structures of liquid-phase GaIn alloy embedded in PDMS with freeze casting. , 2013, Lab on a chip.

[13]  Charles A Rohde,et al.  Capacitive Bio-Inspired Flow Sensing Cupula , 2019, Sensors.

[14]  C. Campenhausen,et al.  Detection of stationary objects by the blind Cave FishAnoptichthys jordani (Characidae) , 1981, Journal of comparative physiology.

[15]  J. Videler,et al.  Energetic advantages of burst-and-coast swimming of fish at high speeds. , 1982, The Journal of experimental biology.

[16]  Jung Woo Lee,et al.  Designing Thin, Ultrastretchable Electronics with Stacked Circuits and Elastomeric Encapsulation Materials , 2017, Advanced functional materials.

[17]  Lijiang Zeng,et al.  Kinematics, hydrodynamics and energetic advantages of burst-and-coast swimming of koi carps (Cyprinus carpio koi) , 2007, Journal of Experimental Biology.

[18]  Rebecca K. Kramer,et al.  Hyperelastic pressure sensing with a liquid-embedded elastomer , 2010 .

[19]  S. Coombs,et al.  Biologically inspired design of hydrogel-capped hair sensors for enhanced underwater flow detection , 2009 .

[20]  A. Kroese,et al.  Frequency response of the lateral-line organ of xenopus laevis , 1978, Pflügers Archiv.

[21]  J. Muth,et al.  3D Printing of Free Standing Liquid Metal Microstructures , 2013, Advanced materials.

[22]  H. Bleckmann,et al.  Determination of object position, vortex shedding frequency and flow velocity using artificial lateral line canals , 2011, Beilstein journal of nanotechnology.

[23]  J. Engel,et al.  Design and Characterization of Artificial Haircell Sensor for Flow Sensing With Ultrahigh Velocity and Angular Sensitivity , 2007, Journal of Microelectromechanical Systems.

[24]  J. Montgomery,et al.  The lateral line can mediate rheotaxis in fish , 1997, Nature.

[25]  A. Hudspeth,et al.  Putting ion channels to work: mechanoelectrical transduction, adaptation, and amplification by hair cells. , 2000, Proceedings of the National Academy of Sciences of the United States of America.

[26]  J. Kosel,et al.  A magnetic nanocomposite for biomimetic flow sensing. , 2014, Lab on a chip.

[27]  Jan Genzer,et al.  Vacuum filling of complex microchannels with liquid metal. , 2017, Lab on a chip.