Security in the shell: An optical physical unclonable function made of shells of cholesteric liquid crystals

Lenzini, Gabriele; Ouchani, Samir; Rønne, Peter B.; Ryan, Peter Y. A.; Geng, Yong; Lagerwall, Jan P. F.; Noh, Jae Hyung

doi:10.1109/wifs.2017.8267644

Cited by 17 publications

(25 citation statements)

References 11 publications

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“…While the initial work, experimental and theoretical, was restricted to nematic shells (orientational order only; molecules aligning along the director n) [4][5][6][7][8][9][10][11], later efforts have focused also on smectic shells of SmA- [12][13][14][15][16][17][18][19] and SmC-type [17] as well as cholesteric [20][21][22][23][24][25][26] shells. Thanks to advances in providing long-term stability through polymerization/polymer stabilization of LC shells [26][27][28][29], they are also emerging as a realistic basis for innovative applications, for instance in photonics and photonics-derived use cases [20,26,27,[30][31][32][33][34][35], sensing [28,36,37] or unconventional soft actuators [38][39][40].…”

Section: Introductionmentioning

confidence: 99%

Dynamic tuning of the director field in liquid crystal shells using block copolymers

Noh

Wang

Liang

et al. 2020

Phys. Rev. Research

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When an orientationally ordered system, like a nematic liquid crystal (LC), is confined on a self-closing spherical shell, topological constraints arise with intriguing consequences that depend critically on how the LC is aligned in the shell. We demonstrate reversible dynamic tuning of the alignment, and thereby the topology, of nematic LC shells stabilized by the nonionic amphiphilic block copolymer Pluronic F127. Deep in the nematic phase, the director (the average molecule orientation) is tangential to the interface, but upon approaching the temperature T NI of the nematic-isotropic transition, the director realigns to normal. We link this to a delicate interplay between an interfacial tension that is nearly independent of director orientation, and the configuration-dependent elastic deformation energy of an LC confined in a shell. The process is primarily triggered by the heating-induced reduction of the nematic order parameter, hence realignment temperatures differ by several tens of degrees between LCs with high and low T NI , respectively. The temperature of realignment is always lower on the positive-curved shell outside than at the negative-curved inside, yielding a complex topological reconfiguration on heating. Complementing experimental investigations with mathematical modeling and computer simulations, we identify and investigate three different trajectories, distinguished by their configurations of topological defects in the initial tangential-aligned shell. Our results uncover a new aspect of the complex response of LCs to curved confinement, demonstrating that the order of the LC itself can influence the alignment and thereby the topology of the system. They also reveal the potential of amphiphilic block copolymer stabilizers for enabling continuous tunability of LC shell configuration, opening doors for in-depth studies of topological dynamics as well as novel applications in, e.g., sensing and programed soft actuators.

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Section: Introductionmentioning

confidence: 99%

Dynamic tuning of the director field in liquid crystal shells using block copolymers

Noh

Wang

Liang

et al. 2020

Phys. Rev. Research

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“…Incorporating anti-counterfeiting tags with physical unclonable functions (PUFs) into objects is a promising solution for their authentication. Ongoing research hints at future LC-based technologies that may benefit from the peculiar behavior of CLCs subject to curvature, as reported for the case of cholesteric shells and droplets with the objective of generating unclonable patterns [72][73][74] .…”

Section: Resultsmentioning

confidence: 99%

Biomimetic design of iridescent insect cuticles with tailored, self-organized cholesteric patterns

2020

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Replicating biological patterns is promising for designing materials with multifaceted properties. Twisted cholesteric liquid crystal patterns are found in the iridescent tessellated cuticles of many insects and a few fruits. Their accurate replication is extremely difficult since discontinuous patterns and colors must coexist in a single layer without discontinuity of the structures. Here, a solution is demonstrated by addressing striped insect cuticles with a complex twisted organization. Geometric constraints are met by controlling the thermal diffusion in a cholesteric oligomer bilayer subjected to local changes in the molecular anchoring conditions. A multicriterion comparison reveals a very high level of biomimicry. Proof-of-concept prototypes of anti-counterfeiting tags are presented. The present design involves an economy of resources and a high versatility of chiral patterns unreached by the current manufacturing techniques such as metallic layer vacuum deposition, template embossing and various forms of lithography which are limited and often prohibitively expensive.

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“…As argued in [29,37], CSR arrays qualify, thanks to their intricate near-field reflection behavior, as optical physical unclonable functions (PUFs) [38,39], of great use in object authentication. Saying that arrays of CSRs are PUFs means that their near-field optical response is physically unreproducible, due to the unpredictability of the exact arrangement of the hundreds of individual CSRs in the array.…”

Section: The Working Principle Of Csrs and Their Implementation In Fiducial Markersmentioning

confidence: 99%

“…In fact, it is in combination with BIM that the full value of CSR fiducials would come to fruition, embracing-first-the utility in far-field read-out for categorization based on the mass-producable fiducial marker pattern generated by all the CSR retroreflection dots connected together (figures 5(c)/(g)). Second, near-field read-out of the detailed optical response at the resolution of individual CSRs (figures 5(h)-(i)), unique to every individual CSR fiducial, would be utilized for reliable authentication [18,29,37]. Because one and the same coating, intimately bound to the carrier, combines both functions, CSR fiducials thus provide a highly valuable tool for secure verification of authenticity and easy categorization, making them the ideal physical-to-digital link for BIM.…”

Section: The Product Stage and The Need For Digital Tracing And Coordinationmentioning

confidence: 99%

Linking physical objects to their digital twins via fiducial markers designed for invisibility to humans

et al. 2021

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Security in the shell: An optical physical unclonable function made of shells of cholesteric liquid crystals

Cited by 17 publications

References 11 publications

Dynamic tuning of the director field in liquid crystal shells using block copolymers

Dynamic tuning of the director field in liquid crystal shells using block copolymers

Biomimetic design of iridescent insect cuticles with tailored, self-organized cholesteric patterns

Linking physical objects to their digital twins via fiducial markers designed for invisibility to humans

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