Forming and Manipulation of Structures of Metallic Microparticles in Suspension in External Alternating Electric Field |
| M. Zientaraa, D. Jakubczykb
apSci Marcin Zientara, Wąwozowa 33 lok. 4, PL-02796 Warsaw, Poland bInstitute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw, Poland |
| Received: October 31, 2018; revised version September 25, 2019; in final form September 26, 2019 |
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| Metallic microparticles, suspended in a dielectric liquid in external alternating electric field, tend to organise into regular structures. Since the structures depend on the external field parameters, they enable testing the general properties of complex systems, as well as engineering new (meta)materials. In our experiments on Cu microparticles suspended in a mixture of rapeseed oil and n-hexadecane in AC field, four system states (structure types) were distinguished and described: (i) driven gas state, (ii) vertical chains, (iii) fully randomly oriented chains, and (iv) percolation state. The states can be rapidly switched by manipulating the amplitude and the frequency of the AC field. The states exhibiting higher and lower order occur alternatingly versus a one-field-parameter scan. Two interstate transitions, involving microstructure reorganisation, were discussed in detail: (1) driven gas-vertical chains state transition and (2) randomly oriented chains-percolation state transition. A simple model of interactions, utilising the concept of a local electric field and considering charges and dipoles interactions,linebreak was proposed to explain the driven gas-vertical chains state transition. The transition was found independent of the external field amplitude, and the transition frequency was found to be only on dependent material properties. A simple formula predicting the transition frequency was obtained. The randomly oriented chains/percolation network transition was discussed in detail. The transition position for external field frequency and amplitude was found unequivocal, though a significant formation/disintegration hysteresis was observed versus both these parameters. The transition was found to be weakly dependent on the microparticle charge and the network formation is expected to be controlled by ohmic current. Thus, a description in the language of electric circuits was proposed for future development. |
DOI:10.12693/APhysPolA.136.866 topics: field-driven assembly, metallic microparticles suspension, microparticles structures, percolation transition |