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Technology and Industrial Applications


In order to apply mechanisms of insect sensory systems, neural information processing in the brain and behavior, two main lines of research are prevalent at present. The first is to learn from the simplicity and efficiency of information processing mechanisms of insect sensory and control systems that often function with amazing speed, sensitivity, and precision and to apply them to improve conventional technology sensors and control systems. The second is to utilize the insects directly though targeted manipulations of sensory and central nervous systems that lead to behavioral control, provinding a simple readout of such a system. These two approaches are also being merged, using both genetic manipulations and interfacing of insects to robots. Such hybrid systems are being used to gain deeper insight into the functions of insect nervous systems with the goal of reconstructing a fully featured insect brain. This information can in turn be applied, especially in autonomous robots.

Some examples of applications that have emerged from studies of insect nervous systems and behavior are listed below.

[Materials]

Spider silk
Compared to conventional silk from moths, that serves purely protective functions, spider silk comes in a wide variety of types that are used for particular applications. In general, spider silk as very interesting mechanical properties, being highly flexible but also very tough. No synthetic fibers can match this peculiar combination of favorable properties. The possibility of producing materials with spider silk properties is being very actively researched.

Material design based on the insect cutile
The exoskeleton of arthropods consists of cuticle, a layered composite material whose properties are variable both during the life cycles of arthropods and between species and higher taxonomic groups. Chitin nanomaterials, proteins, and waxes are combined to a lightweight rigid structure with high resistance to wear. Looking at a dragonfly wing for instance makes it obvious that a similar synthetic material would lead to a revolution and replace current light-frame construction methods.

Application of insect pwing to flexible robot joints
Insect appendages, in particular those for locomotion, swimming, and flight make use of resilin, a highly elastic protein, for supporting translation of muscle contractions into movements. Insects use resilinfs elasticity to fly and jump: consider the extreme case of fleas, that can jump over distances more than 100 times their own body length. Many applications are in need of a material with the astonishing properties of resilin. High elasticity means small energy loss but also enhanced flexibility, which could improve joints in many systems, including robots, whose operation could become more supple, with increase safety margins.

[Sensory systems]

Odor sensors
Insects posess olfactory systems that set landmarks in terms of sensitivity and selectivity. Intensive research of the past decades has recently lead to the elucidation of the primary processes of olfaction in insects. The key advantage of odorant sensors in insects is direct coupling between chemical detection and electrical transduction in a single protein complex. As genetic tools are readily available for making these sensors available, the development of fast, highly sensitive and highly selective odorant sensors is currently under way.

Odor source localization robot
Already the French naturalist Henri Fabre observed that moths are capable to localize an odor source, a conspecific female, from a distance up to several kilometers. This obviously requires not only very sensitive and specific odorant sensors but also a suitable strategy to cope with environmental conditions in the natural surroundings. Copying the behavioral strategy used by moths and other insects in localizing odor sources is a promising approach currently being employed to develop robust odor-source localisation robots.

A flow sensor using an artifical sensory hair
Many arthropods are highly sensitive to minute air currents. Particularly well-studied examples are crickets, which bear a number of filiform hairs on their cerci as well as spiders (Cupiennius salei and Agelena sp.), and whip scorpions, that have trichobothria. All these hair sensilla specialised for the detection of small air currents are very fine and relatively long hair sensilla with specially adapted socket structures. Taking advantage of the ultrastructural information available for such sensilla, efforts are being made to implement corresponding sensors in MEMS.

Visual naviation in the deset ant
The interaction of sunlight with the athmosphere results in a polarization pattern in the sky, that varies with the position of the sun. Polarization is strongest opposite to the sun. If the sun is not directly visible, the polarization pattern can be used to infer the position of the sun. The dorsal part of the compound eye of many insects contains specialised photoreceptors that are polarization-sensitive. Polarization sensitivity (dichroism) results from the arrangement of membrane evaginations called microvilli that are oriented in one direction with respect to the long axis of the photoreceptor, that coincides with the axis along which light travels as projected by the lens of the ommatidium. Polarization-sensitive receptors are short and each has all its microvilli oriented in one direction (Bernard and Wehner). All other polarization-insensitive receptors in the rest of the eye are longer and twisted such that microvilli are oriented in all possible directions, abolishing dichroism. The detection of the orientation of polarized light by receptors with differently oriented microvilli (and scanning the sky if there are only receptors with two orientations) and the overall polarization pattern in the sky thus enables these insects to infer sun position without direct visibility of the sun. In bees, it has been shown that they also have a clock to compensate for the course of the sun over the time of the day enabling them to infer the direction to the hive from the position of the sun at all times (Renner). As a result, homing is always possible using these external and internal references. Recently, it has also been shown that polarized light orientation is possible in moonlight in a dung beetle (Warrant et al, Nature).

Sound orientation in the cricket
The cricket has tympanal organs on the tibiae of the front legs. The left and right tympanal organs are connected through an acoustic trachea. Sound from both sides can interact to result in amplification or attenuation though this structure. The female cricket use the tympanal organs in particular for localising a calling male (that is, if she want him...). Sound localization under natural environmental conditions is not a trivial task. Sound can be reflected, other sounds can interfere, etc. Thus, sound localization in crickets is a very useful system to investigate how to solve this task under natural conditions, conditions under which it is difficult for man-made systems to operate reliably.

[Robot control]

A visually guided robot inspired by the fly
A prominent feature of insect eyes is their enormously high flicker fusion frequency. In some insects, time resolution goes up to over 200Hz, but spatial resolution of compound eyes is limited. For insects, rapid detection motion is of utmost importance for course control. In seminal experiments using a curculionid beetle walking on a Spangenglobus, Hassenstein and Reichart have described behavioral rections to visual motion and Reichart proposed an elegant model for motion detection (based on autocorrelation of visual inputs) that has been one of the biggest successes of theoretical neuroscience. Later, Hausen recorded neurons from the fly's lobula plate that show responses that are exactly predicted by Reichart's autocorrelation detector model. The success of this model is also shown by a number of robotic implementations that use Reichart detectors for motion detection and course control.

A flight-stabilizing device based on ocelli
Ocelli are visual sensory organs of insects separate from the compound eyes. Most insects have ocelli, in general three of them. The resolution of the ocelli is too low for detailed images and the visual fields covered are large but contrast detection is possible. Depending on body tilt, the distribution of light intensity received by the different ocelli changes and this information is being used as a gyroscope.

Robots using insect design principles
Insects may have tiny brains, but they are capable of a wide variety of behaviors. Most striking and obvious are their capabilities in walking and flying. Even these tasks are difficult to reproduce by machines built according to traditional design principles. Therefore, numerous investigators are working on attempts to emulate the insects' highly elaborate motor systems. On the one hand, insects are used to steer robots through their behavior to be able to investigate movement patterns in detail under defined conditions and even in the presence of perturbations which can be chosen by the experimenter. This approach is very promising for characterising insect locomotion or flight in great detail. On the other hand, a chosen physiological parameter, the activity of well-defined neurons for example is used to steer a robot. This makes it possible to go beyond phenomenological analysis and allows direct testing of candidate neural codes for generating behavior.

An insect-based flying robot
The miniaturization realised in insects has stunned many early philosophers and later scientists. And these minatures show complex behaviors, too. However, a first step that is a considerable technological challenge is the reconstruction of the mechanical aspects of such systems at this small scale. This has motivated many studies in particular on insect flight biomechanics with the aim to understand how a flying robot can be realised a such scale. Detailed knowledge has been accumulated so that the aim of an autonomous flying system in insect size seems realistic.

Insect walking and a walking-controlled robot
Insects (also known as Hexapods) have six legs in many insects, these six legs are also used for locomotion. Characterisitc of such walking insects is the trip gait in which three legs (two one one side) swing and the remaining legs have ground contact to support the body. The most important properties of the neural networks generating walking patterns have been elucidated and as a result, insect-like hexapod robots have been successfully implemented. An advantage of hexapod robots (and their insect models) is the high stability and robustness to disturbances of locomotion.

[Controlling insect behaviors]

Remote control of insect behaviors
DARPA funds a line of research that aims to control insect behaviors though a tiny remote-controlled stimulation apparatus carried by the insects.

[Others]

An architecural insecticide method based on insect traits
Of course, insect-free environments are not really desirable... But since some insect pests have high economic importance and insecticides have too many hazards, civil and structural engineering gradually shift towards methods to make buildings insect-proof using information on their behavioral ecology. Such methods are particularly important to prevent contamination and damage to stored goods, in particular food.


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