La vibration des insectes, une inspiration pour la science
Among the flying species observed in nature, insects certainly have the most impressive aerial capacities in terms of hovering or acceleration, and remain unequalled on these scales in terms of weight, size and energy efficiency. While understanding the mechanisms of flight has long been elusive, we now know that the key to such performance lies mainly in the specific movements obtained thanks to their flexible wings and the unsteady aerodynamic forces generated. A bio-inspired approach therefore seems to be a promising way of designing flying nano-robots.
The aim of the project entitled "nano-robot based on the control of vibrating wings" (NANOFLY) falls into this category, since it involves creating an insect-sized object, powered by electrical wires, capable of taking off and hovering.
Video 1: Operating the wings
Video 2: Lifting the nanobot attached to a rigid beam
Initial developments have already led to major advances: the NANOFLY team was the first to use microsystems technologies [1] to manufacture the skeleton of the nanobot, which has a wingspan of 25 mm. Its design is directly inspired by the order of diptera and consists of a support, a mobile part - a tergum and two wings - and a fixed part - the thorax (Fig. 1). The use of optical photolithography and etching processes offers the advantage of being rapid and reproducible, and has led to the production of a skeleton in SU-8 polymer resin with thicknesses varying between 0.4 mm and 0.3 mm, as well as membranes for the wings in Parylene material with thicknesses equal to 400nm. Just as insects use their muscles to vibrate their thorax and drive their wings at several hundred beats per second, we decided to work with an entirely resonant system, without joints, excited by an electromagnetic actuator and with flexible wings to amplify the movement. In addition, our originality lies in using a principle of combining two vibratory modes of bending and torsion of the wings in phase quadrature [2], to reproduce the appropriate kinematics. Initial tests have demonstrated that a lift force equivalent to the weight of the prototype (22mg) can be obtained, with respective values of 30° and 15° for the flapping and tilting angles of the wings (Fig.2).
The current challenges concern the take-off of the nano-robot [3]: firstly, the aim is to better understand the effects of aeroelastic coupling in order to obtain a lift force 3 times greater than the weight of the prototypes. It is essential to increase this lift force if the nano-robot is to be able to take off carrying a payload. The second challenge is to stabilise the nano-robot during hovering flight for a minimum of 10 s, which means strengthening the flight control system and implementing the electronic functions needed for remote control. The third challenge involves scientific and technological monitoring with a view to ensuring the nano-robot's long-term autonomy and its use for reconnaissance missions. This involves analysing current and future solutions for miniaturising and lightening the existing electronic board and identifying the appropriate payload and energy sources by choosing low-mass components and sensors requiring very few energy resources. Among the avenues envisaged, we will be looking in particular at hybrid electronic circuits, CMOS micro-cameras and super-capacitors.
Fig. 1. a) Exploded view of the various prototype components
Fig. 1 (b) prototype nanobot with a wingspan of 25 mm and a total weight of 22 mg.
Fig. 2. a) Experimental deformations at resonance: bending and torsion modes, b) Frequency Response Function of the prototype taken at the left wing tip of the leading edge, zoomed in on the frequency range of interest. c) Average lift force for several excitation frequencies with adjustment using a polynomial curve.
Références :
[1] Bao, X. Q., et al. "Design and fabrication of insect-inspired composite wings for MAV application using MEMS technology. Design and fabrication of insect-inspired composite wings for MAV application using MEMS technology." Journal of Micromechanics and Microengineering 21.12 (2011): 125020.
[2] Faux, D., Thomas, O., Cattan, E., & Grondel, S. (2018). Two modes resonant combined motion for insect wings kinematics reproduction and lift generation. Europhysics Letters, 121(6), 66001.
[3] Grondel, Sébastien, et al. "Towards the use of flapping wing nano aerial vehicles." Modern Technologies Enabling Safe and Secure UAV Operation in Urban Airspace 59 (2021): 52.
Dissemination to the general public :
1. E. Cattan
The world's smallest drone presented in Valenciennes, Journal Télévisé France 3, 19/20 Nord Pas-de-Calais, 10 October 2023
https://france3-regions.francetvinfo.fr/archives/2023/10-octobre-2023
2. E. Cattan, S. Grondel, When nature inspires innovation, Exhibition at IMTD, 10 October 2023
https://imtd.fr/evenements/expo-nature-inspire-innovation/
3. S. Grondel, E. Cattan, Ces chercheurs qui se sont mis en tête de faire voler un drone de la taille d'une mouche, La Voix du Nord, 4 October 2023.
https://www.lavoixdunord.fr/1381005/article/2023-10-04/ces-chercheurs-qui-se-sont-mis-en-tete-de-faire-voler-un-drone-de-la-taille-d
4. S. Grondel, H. Poirier, Du microrobot au nanorobot, France Culture, Continent sciences, 30 May 2016
https://www.radiofrance.fr/franceculture/podcasts/continent-sciences/du-microrobot-au-nanorobot-2637360
5. S. Grondel, Le robot-beeille, Science & Vie, n°1185, 58-59, June 2016,
https://www.science-et-vie.com/article-magazine/robot-abeille-ses-ailes-vibrantes-reinventent-le-vol
