Introduction to Biomimetics

Biomimetics

• Biomimicry involves emulating natural models, systems, and elements to tackle human/engineering problems.
• Natural selection promotes good adaptations.
• Biomimetics applies on both macro and nano scales.
• Nature has solutions for self-healing, hydrophobicity, self-assembly, utilization of solar energy, and tolerance/resistance to environmental factors.

Biomimetics - History

• Leonardo da Vinci's plans for human flight exemplify early biomimicry.
• Observation of bird anatomy and flight was crucial.

Biomimetics - Inspiration

• Flying, implants, artificial intelligence, synthetic life, gene technologies, and genetic algorithms are all inspired by nature.
• Structures like beehives and biologically inspired mechanisms (controlled adhesion) are mimicked.
• Materials like spider webs (strong fibers) and biosensors.

Biomimetics - Basic Concept, Design Concept Questions

• Questions used in biomimetic design include:
  • What does the system do?
  • How is the system unique?
  • How does the system carry out its functions?
  • Under what conditions does the system operate?
  • What kinds of relationships exist between functional requirements?
  • What compromises are required?

Biomimetic Methodology Framework - Example - Exoskeleton Design

• The stages for biomimetic exoskeleton design include, review of related literature, user needs analysis, identifying the biological analogue, formulating technical specifications, computer-aided design (CAD), parts and assembly generation, forward kinematic analysis, prototype development, integration of mechanical, electrical, and software components, testing and validation (including kinematic compatibility analysis, alpha testing and validation by medical experts).

Challenges and Prospects

• Challenges in biomimicry include understanding natural mechanisms, discovering new bionic materials and structures, system establishment and optimization, ultra-sensitivity, self-adaptability, multi-sensor coupling, miniaturization, and low energy use.
• Prospects for biomimicry involve developing new sensing mechanisms, advanced manufacturing technology, construction and development of closed-loop systems.
• Additional prospects include creating multi-functionality, high integration, artificial intelligence, self-optimization, and self-powering.

Snake - Infrared Thermography

• Infrared (IR) detectors allow snakes (pit vipers and boids) to perceive heat distribution.
• They can form a thermal image of prey or predators for hunting or survival.
• IR detectors work even in pitch darkness.

Infrared Thermography - Anatomical Structure

• Pit organs exist on each side of the snakes' heads near their eyes(pit vipers) or located between the eye and nostril(rattlesnakes)
• Thin membranes act as antennae for IR detection
• Snakes detect temperature differences in the millikelvin (mK) range.

Infrared Thermography - Anatomical Structure of the Pit Organ

• The air-filled pit organ chamber provides surrounding air contact.
• Pit organs contain mitochondria-rich, highly vascular tissue.
• The tissue has heat-sensitive receptors formed from terminal nerve masses.
• Signals travel from pit organs to optic tectum in the brain, from high-water concentration to mid-infrared-region of electromagnetic spectrum, using highly absorbent tissue.

Infrared Thermography - Physiology

• Two main IR transmission regions: 1700-2900 cm⁻¹ (3.4-6.0 µm), and 700-1200 cm⁻¹ (8.3-14 µm).
• Photochemical transduction uses transient receptor potential proteins.
• "Wasabi receptor" (TRPA1) detects heat.
• Rattlesnakes are active above 28.0±2.5 °C (thermally inactive at room temperature).

Infrared Thermography - Hemispherical Biomimetic Pit Organ

• Germanium has high light transmittance in the 7-14 µm wavelength range and blocks visible light.
• Image sensor has 625 pixels with 550 µm pitch.
• Manufacturing accuracy limits pixel density.

Infrared Thermography – Applications

• Applications include landing space shuttles, PCB hotspot detection, transmission line monitoring, motor monitoring, building and chimney analysis, human and cat thermal imaging, medical uses, and COVID-19 screening at airports and medical facilities.

Medical Thermography

• Medical thermography is used for diagnostics, by measuring heat emitted from the skin.
• Moisture, airflow and surrounding temperature are critical factors in thermography experiments.
• The temperature change during the experiment should be within a few degrees.
• Room temperature and acclimation time are important.
• This is used for example to detect breast cancer and diabetes

Bat's Echolocation

• Bats use ultrasonic sound and their auditory systems to navigate and hunt.
• The sounds compare outgoing sounds to returning echoes to depict the surrounding environment.
• The echolocation pulses vary depending on the species and hunting strategy.
• Bats use echo timing, frequency content, duration, and intensity for efficient prey capture.

Bat's Echolocation - Types

• Frequency modulated (FM) signals and constant frequency (CF) signals help with orientation and foraging.
• CF components have frequencies near 27 kHz and durations ranging from 20 to 200 milliseconds.
• FM components sweep in frequency (down from 24 to 12 kHz) with harmonic sounds in the 40-22 kHz range.
• Narrowband CF signals help determine target location and velocity.
• FM signals create multi-dimensional acoustic pictures for target identification

Bat's Echolocation - Neurobiology

• The bat's ear has specialized cochlea which is suitable for high-frequencies.
• Muscles control signal amplitude to/from cochlea

Bat's Echolocation - Physics

• The range equation S ≈ PGAσ/(16π²R⁴e⁻²BR) quantifies the power of signal received by bat.
• P equals the acoustic power sent, S is the power received.
• G equals transmitter gain, A is antenna area, R is range from target and σ is acoustic cross-section (echo area).
• β is the atmospheric attenuation factor; it depends on frequency.
• σ depends on target insect shape and size (e.g., higher for larger insects).

Bat's Echolocation - Physics

• Physiological adaptations to the ear and the brain enable the detection of small reflected signal power.
• Filtering with specific frequencies (similar to those emitted) is important.
• Head-related transfer functions help locate sound sources.
• Interaural intensity differences, and spectral cues are part of that process.
• Bats can detect very small sources in both azimuth and elevation.

Echolocation - Engineering Implementation

• Radar uses electromagnetic waves to measure range, altitude, and speed of objects.
• Microwaves and radio waves are used for these calculations.
• This is done using a transmitter which sends waves that are reflected by targets and picked up by a receiver.
• Radar senses changes in dielectric or diamagnetic constant (e..g solid objects in air).

Echolocation - Engineering Implementation

• In virtual environments, an emitted pulse centered on the user's head acts as a marker and intensity indicator.
• The virtual environment renders the return pulse at the target location using the sender-to-target-to-sender round trip time delay.
• This system is applied in mobile robotics and orientation.
• Doppler shift mechanisms are also utilized for orientation.

Insects - Acoustical Defense

• Insects have evolved defence mechanisms to evade bat hunting.
• Insects exhibit hearing in the 10-80 kHz range.
• Defence mechanisms include aposematism (warning signals linking sound to noxious qualities like bad taste) and jamming (using similar noise to confuse and break the bat's focus on a target).
• Other mechanisms involve startle responses (quick sounds to cause temporary confusion).

Insects - Auditory Mechanism

• Moth ears have three mechanosensory neurons including 2 auditory and one sensitive cell.
• Sound clicks are generated using mechanisms like stridulatory organs, that involve a part of the forewing and tibia in hind legs, to create specific sounds.

Insects - Jamming - Engineering Adaptation

• Lockheed F-117 Nighthawk aircraft uses a similar technique in jamming radar, which involves adapting the aircraft's shape to deflect radar signals.
• Using different composite materials, scattering and refracting incoming waves makes it harder for radar systems to detect the craft.

Dolphin, Whale - Sonar

• Dolphins and whales live in underwater environments with limited visibility (from meters to tens)
• Acoustic energy travels better underwater compared to light
• These animals have evolved advanced acoustic systems.
• Blue Whales' frequency range is from 15 Hz, whereas Odontocetes use higher frequencies (over 100 kHz). This is due to the anatomical limits of these animals.

Sonar - Physiology

• Odontocetes produce high-frequency sounds (whistles, burst pulses, clicks)
• Mysticetes produce low-frequency sounds.
• These sounds are generated by the cetacean's body.

Sonar – Utilization by Cetaceans

• Echolocation is used for prey detection & navigation.
• Cetaceans have 10 – 200 ms inter-pulse intervals.
• Dolphins have unique whistle signatures with frequency-modulation patterns.
• Whales have songs (involving patterns of sounds) used for social life and emotional expression, possibly even forms of communication.

Sonar - Engineering Adaptation

• Bioinspired sonar systems utilize small unmanned underwater vehicles (UUVs).
• Technologies employ dense array configurations for detecting targets.
• Examples include underwater-navigating robots, ultrasound sonar for distinguishing trees from metal poles, and outdoor mobile robot navigation.

Medical Ultrasound

• Medical ultrasound uses the principles of echolocation.
• Ultrasound is relatively cheap, portable, fast, and is relatively safe, with few known side effects.
• Disadvantages include qualitative and poor image quality; depth-resolution trade-off is a factor.

Medical Ultrasound

• Ultrasound uses frequencies from 2–15 MHz in humans.
• Sound speed is around 1540 m/s.
• The penetration ranges from 0.77 to 0.10 mm.
• Attenuation is related to frequency, with a higher frequency increasing signal loss.

Medical Ultrasound - B-Mode Imaging

• A-mode shows amplitude, while B-mode creates a display of the envelope of the A-lines.
• Images are constructed using multiple reflections from boundaries.

Medical Ultrasound - Transducer

• Transducers come in linear array, curved array, phased array, and sector scan varieties.

Medical Ultrasound - Beamforming

• Linear array transducers use high frequencies (5-10 MHz) for higher resolutions (0.2 mm) but shorter penetration depths (10 cm).
• These are good for organs like abdominal organs.
• Phased array transducers use lower frequencies (1-4 MHz) for large penetration depths (30 cm), but for lower resolution (0.6 mm).
• These are good for hard-to-access organs like the heart.

Medical Ultrasound - Transducer

• 1D and 2D array apertures are used in linear and phased array beam-forming respectively.
• Linear beam forming uses a single aperture across the sensor's length
• Phased array beam forming uses multiple, individual apertures across the sensor's length

Medical Ultrasound - Doppler

• Doppler techniques measure the velocity of blood or other tissue movement.
• These techniques use the changes in frequency reflected from moving targets.
• Used to display blood/tissue flow and movement.

Medical Ultrasound - Applications

• Medical ultrasound applications include angiology, cardiology, gastroenterology, dermology, pulmonology and gynecology

Hair Cells - MEMS Technology

• The monitoring of air and water flow on a micro-scale.
• Clusters of hair-cells in insects and fish are used for nerve-cell stimulation from cilia bending (caused by flow).

Hair Cells - Airflow

• Two types of artificial hair cell sensors exist.
• Type 1 has a cantilever parallel to the substrate, detecting force components acting on front and back sides.
• Type 2 uses a thin wire on a cross-shaped beam with strain gauges for acceleration/velocity detection.

Hair Cells - Airflow

• Other type of cantilever sensor is perpendicular to the substrate.
• Early types are brittle silicon while their improvements are made with a robust polymer base.

Hair Cells - Waterflow

• Fish have superficial neuromasts that consist of support cells, mantle cells, and hair cells with cilia.
• The structures are adapted for sensing water flow.

Whiskers - Collision Detection

• Whiskers are sensitive for collision detection and finding food.
• This is used to simulate a similar system for robotic or biological inspired systems.
• The leverage effect helps to amplify weak touch signals.

Whiskers - Collision Detection

• The illustration shows the brain, sensing nerve, mechanoreceptors, and biomimetic structures of whiskers.
• These structures help in sensing objects/surroundings

Whiskers - Surface Recognition

• Electronic whisker sensors enable surface recognitions.
• The sensor measures the changes in charge based on the surface properties.
• These sensors are used in a mobile robot or similar platform..

Whiskers - Shape Recognition

• Techniques for recognizing shapes using whisker-inspired robots.
• A method using a permanent magnet, bending and protraction angles is illustrated.
• The method also involves an aluminium base, motor axis, distance, and rotational angle.

Summary - Questions

• Key questions on biomimicry, snake thermovision, IR camera applications, bat echolocation, insect defence, sonar, ultrasound imaging, hair cell mechanisms, biomimetic whisker functioning are asked.

References

• A list of scholarly articles and conference papers relevant to each topic can be found here.