Research

Shape-morphing structures

Shape-morphing structures are designed to change shape in predictable ways in response to external or internal stimuli. They are literally everywhere around us (think of a foldable camping chair). Typically, these structures are made up of multiple jointed parts. One of the goals of our research is to develop new morphing paradigms to reduce the high part count typical of deployable systems. We do so by resorting to monolithic structures with complex architectures where the joints are replaced by compliant hinges, trying not to sacrifice the structural performance. While we are not opposed to the use of polymeric specimens during the development of new shape-morphing concepts, our final objective is always the realization of deployable structures made of structural materials like metals, wood and composites. Beyond idea development, we are also interested in developing computational frameworks for the inverse design of such structures, starting from prescribed target shapes.


 

Wave mechanics and metamaterials

One of our core interests is the design of structural systems that can manipulate mechanical (elastic and acoustic) waves in unprecedented ways. These systems typically showcase some combination of unusual effective properties such as negative mass, negative stiffness or negative bulk modulus, and for this reason they are known as metamaterials/metastructures. Among other effects, they allow to filter and confine waves, and to cloak and manipulate objects. Currently, we are particularly interested in metamaterials for the manipulation of surface waves, that manifest themselves at the edge of semi-infinite media and are relevant in many contexts, from seismic events to telecommunication devices and microfluidics. Another goal of ours is to develop strategies for active wave control (see the Adaptive/Smart systems section).


 

Adaptive/Smart systems

We are interested in creating concepts for structures that can adapt to the environment around them. In the context of shape-morphing systems, we are mainly interested in passive actuation, i.e., in leveraging heat, humidity and atmospheric inputs for adaptation. Examples of applications of such systems are adaptive building envelopes or structures designed to morph during the day/night lunar cycle. Based on this idea, we developed bi-metallic structures capable of extreme thermal expansion in response to temperature variations;. In the context of wave control, we developed concepts for reconfigurable/tunable systems, whose properties can be altered by leveraging non-mechanical (e.g., electrical or magnetic) stimuli. Our goal, however, is true adaptivity: designing structures featuring networks of sensors and actuators, that can adapt and respond to the characteristics of a certain wave/disturbance.


 

Experimental mechanics and structural dynamics

We pride ourselves in being able to create low-cost, yet precise experimental setups for tabletop-scale mechanics testing. Our craft is particularly developed for vibrations/modal analysis and wave mechanics testing (especially in the realm of lattice structures and metamaterials), and it stems from a thorough understanding of the mechanics involved and of the influence of boundary attachment, actuator types and imperfections.

 

Publications (Google Scholar)

  1. S. Injeti, P. Celli, K. Bhattacharya, C. Daraio, Tuning acoustic impedance in load-bearing structures, arXiv 2106.10573 (2021). Link

  2. P. Celli, A. Palermo, Time-modulated inerters as building blocks for nonreciprocal mechanical devices, Journal of Sound and Vibration 572 (2024), 118178. Link, arXiv

  3. S. Hajarolasvadi, P. Celli, B. Kim, A. Elbanna, C. Daraio, Experimental Evidence of Amplitude-Dependent Surface Wave Dispersion via Nonlinear Contact Resonances, Applied Physics Letters 123 (2023), 081704. Link, arXiv

  4. P. Celli, I. Nunzi, A. Calabrese, S. Lenci, C. Daraio, Sparse metapiles for shear wave attenuation in half-spaces, Journal of Vibration and Acoustics 145 (2023), 051003. Link, arXiv

  5. Y. Zheng, I. Niloy, I. Tobasco, P. Celli, P. Plucinsky, Modelling planar kirigami metamaterials as generalized elastic continua, Proceedings of the Royal Society A 479 (2023), 20220665. Link, arXiv

  6. Y. Zheng, I. Niloy, P. Celli, I. Tobasco, P. Plucinsky, Continuum field theory for the deformations of planar kirigami, Physical Review Letters 128 (2022), 208003. Link, arXiv

  7. C. McMahan, A. Akerson, P. Celli, B. Audoly, C. Daraio, Effective continuum models for the buckling of non-periodic architected sheets that display quasi-mechanism behaviors, Journal of the Mechanics and Physics of Solids 166 (2022), 104934. Link, arXiv

  8. S. Taniker, V. Costanza, P. Celli, C. Daraio, Capacitive temperature sensing via displacement amplification, IEEE Sensors 22 (2022), 10388-10395. Link, arXiv

  9. P. Celli, M. Porfiri, The detection matrix as a model-agnostic tool to estimate the number of degrees of freedom in mechanical systems and engineering structures, Chaos 32 (2022), 033106. Link, arXiv

  10. G. Kim, C. Portela, P. Celli, A. Palermo, C. Daraio, Poroelastic microlattices for underwater wave focusing, Extreme Mechanics Letters 49 (2021), 101499. Link

  11. K. Pajunen, P. Celli, C. Daraio, Prestrain-induced bandgap tuning in 3D-printed tensegrity-inspired lattices, Extreme Mechanics Letters 44 (2021), 101236. Link, arXiv

  12. F. Agnelli, P. Margerit, P. Celli, C. Daraio, A. Constantinescu, Systematic two-scale image analysis of extreme deformations in soft architectured sheets, International Journal of Mechanical Sciences 194 (2020), 106205. Link, arXiv

  13. A. Palermo*, P. Celli*, B. Yousefzadeh, C. Daraio, A. Marzani, Surface wave non-reciprocity via time-modulated metamaterials, Journal of the Mechanics and Physics of Solids 145 (2020), 104181. Link, arXiv
    * Equal contribution

  14. P. Celli*, A. Lamaro*, C. McMahan*, P. Bordeenithikasem, D. Hofmann, C. Daraio, Compliant morphing structures from twisted bulk metallic glass ribbons, Journal of the Mechanics and Physics of Solids 145 (2020), 104129. Link, arXiv
    * Equal contribution

  15. O. Bilal, V. Costanza, A. Israr, A. Palermo, P. Celli, F. Lau, C. Daraio, A Flexible Metasurface as a Versatile Haptic Interface, Advanced Materials Technologies 5 (2020), 2000181. Link

  16. S. Taniker, P. Celli, D. Pasini, D. Hofmann, C. Daraio, Temperature-induced shape morphing of bi-metallic structures, International Journal of Solids and Structures 190 (2020), 22-32. Link, arXiv

  17. A. Palermo, Y. Wang, P. Celli, C. Daraio, Tuning of Surface-Acoustic-Wave Dispersion via Magnetically Modulated Contact Resonances, Physical Review Applied 11 (2019), 044057. Link

  18. P. Celli, B. Yousefzadeh, C. Daraio, S. Gonella, Bandgap widening by disorder in rainbow metamaterials, Applied Physics Letters 114 (2018), 091903. Link, arXiv

  19. P. Celli, C. McMahan, B. Ramirez, A. Bauhofer, C. Naify, D. Hofmann, B. Audoly, C. Daraio, Shape-morphing architected sheets with non-periodic cut patterns, Soft Matter 14 (2018), 9744-9749. Link, arXiv

  20. P. Celli, W. Zhang, S. Gonella, Pathway towards programmable wave anisotropy in cellular metamaterials, Physical Review Applied 9 (2018), 014014. Link, arXiv

  21. P. Celli, S. Gonella, V. Tajeddini, A. Muliana, S. Ahmed and Z. Ounaies, Wave control through soft microstructural curling: bandgap shifting, reconfigurable anisotropy and switchable chirality, Smart Materials and Structures 26 (2017), 035001. Link, arXiv

  22. D. Cardella*, P. Celli* and S. Gonella, Manipulating waves by distilling frequencies: a tunable shunt-enabled rainbow trap, Smart Materials and Structures 25 (2016), 085017. Link, arXiv
    * Both authors contributed majorly to the realization of this work

  23. P. Celli and S. Gonella, Manipulating waves with LEGO bricks: A versatile experimental platform for metamaterial architectures, Applied Physics Letters 107 (2015), 081901. Link, arXiv
    >> CEGE News (Link), Physics World (Link), APS News (Link), ScienceNews (Link) <<

  24. P. Celli and S. Gonella, Tunable directivity in metamaterials with reconfigurable cell symmetry, Applied Physics Letters 106 (2015), 091905. Link

  25. P. Celli and S. Gonella, Low-frequency spatial wave manipulation via phononic crystals with relaxed cell symmetry, Journal of Applied Physics 115 (2014), 103502. Link

  26. P. Celli and S. Gonella, Laser-enabled experimental wavefield reconstruction in two-dimensional phononic crystals, Journal of Sound and Vibration 333 (2014), 114-123. Link
    >> featured on the 2015 edition of Polytec InFocus Magazine (pp. 32-35, Link) <<