Browsing by Author "Baytekin, Bilge"

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Open Access
A dormant reagent reaction-diffusion method for the generation of Co-Fe Prussian Blue analogue periodic precipitate particle libraries
(Wiley-VCH GmbH, 2023-08-25) Tootoonchian, Pedram; Kwiczak-Yiğitbaşı, Joanna; Turab Ali Khan, Muhammad; Chalil Oglou, Ramadan; Holló, G.; Karadaş, Ferdi; Lagzi, I.; Baytekin, Bilge
Liesegang patterns that develop as a result of reaction-diffusion can simultaneously form products with slightly different sizes spatially separated in a single medium. We show here a reaction-diffusion method using a dormant reagent (citrate) for developing Liesegang patterns of cobalt hexacyanoferrate Prussian Blue analog (PBA) particle libraries. This method slows the precipitation reaction and produces different-sized particles in a gel medium at different locations. The gel-embedded particles are still catalytically active. Finally, the applicability of the new method to other PBAs and 2D systems is presented. The method proves promising for obtaining similar inorganic framework libraries with catalytic abilities. © 2023 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH.
Open Access
A perspective on plant robotics: from bioinspiration to hybrid systems
(IOP Publishing Ltd., 2022-11-25) Meder, F.; Baytekin, Bilge; Dottore, E. D.; Meroz, Y.; Tauber, F.; Walker, I.; Mazzolai, B.
As miscellaneous as the Plant Kingdom is, correspondingly diverse are the opportunities for taking inspiration from plants for innovations in science and engineering. Especially in robotics, properties like growth, adaptation to environments, ingenious materials, sustainability, and energy-effectiveness of plants provide an extremely rich source of inspiration to develop new technologies—and many of them are still in the beginning of being discovered. In the last decade, researchers have begun to reproduce complex plant functions leading to functionality that goes far beyond conventional robotics and this includes sustainability, resource saving, and eco-friendliness. This perspective drawn by specialists in different related disciplines provides a snapshot from the last decade of research in the field and draws conclusions on the current challenges, unanswered questions on plant functions, plant-inspired robots, bioinspired materials, and plant-hybrid systems looking ahead to the future of these research fields.
Open Access
Anisotropic actuation in salty agarose gel actuators
(Springer, 2023-08-01) Tootoonchian, Pedram; Bahçeci, Levent; Baytekin, Bilge
When hydrogels that can reversibly dehydrate/rehydrate are physically combined with a constant water supply, the cycles can be controlled by on/off states and the positions of an external light source. The shrinking upon dehydration upon illumination causes bending towards the light source, and rehydration in the light-off state restores the initial shape. This simple material feedback mechanism mimics the self-regulating heliotropism (sun tracking) and nyctinasty (leaf opening) movements of plants. In this work, we show the effect of some common salts on the bending behavior of actuators entirely made of hydrogel. The ‘salty’ actuators exhibit different motion kinetics regarding the unique chemical characteristics of each ion. We display that this chemistry of ions also enables us to program the kinetics in a single actuator using the differences in evaporation/diffusion rate of water in the salty gels. This programmability of the motion in a hydrogel actuator with the inclusion of salts can be used to achieve complex behavior observed in living organisms straightforwardly.
Open Access
Bioaromatic-associated multifunctionality in lignin-containing reversible elastomers
(American Chemical Society, 2023-07-12) Thys, Marlies; Kaya, Görkem Eylül; Soetemans, Lise; Van Assche, Guy; Bourbigot, Serge; Baytekin, Bilge; Vendamme, Richard; Van den Brande, Niko
The unique molecular structure of lignin, intrinsically rich in bioaromatic groups (phenolic hydroxyls), gives it, e.g., antioxidant, antistatic, antimicrobial, UV-blocking, hydrophobic, or even flame-retardant properties, which are highly interesting. An attractive strategy to use lignin as a macro-monomer for the design of functional materials that retain certain of these lignin-specific properties is to partially preserve some phenolic groups during the synthesis. In this work, we explore the properties of reversible elastomers containing a lignin fraction whose phenolic groups have only been partially modified. To do so, Kraft lignin was first fractionated and partially (89%) modified with furan groups, allowing its homogeneous incorporation in Diels-Alder formulations. The effect of the residual phenolic groups embedded in the polymer matrix was then systematically studied, focusing on the specific material properties associated with lignin. The obtained lignin-containing networks notably showed increased radical scavenging activity (which directly resulted in improved antistatic and antioxidant properties), displayed improved UV absorbance due to the presence of multiple lignin chromophores, and were even able to inhibit the growth of bacteria. This article demonstrates that tailored and partially modified lignin fractions could be used as multi-functional building blocks for the design of complex (and reversible) polymer architectures, mimicking some of the unique lignin functionalities found in nature, and this without the need to add specific additives.
Open Access
The charging events in contact-separation electrification
(Nature Publishing Group, 2018) Musa, Umar G.; Cezan, S. Doruk; Baytekin, Bilge; Baytekin, H. Tarık
Contact electrification (CE) - charging of surfaces that are contacted and separated, is a common phenomenon, however it is not completely understood yet. Recent studies using surface imaging techniques and chemical analysis revealed a 'spatial' bipolar distribution of charges at the nano dimension, which made a paradigm shift in the field. However, such analyses can only provide information about the charges that remained on the surface after the separation, providing limited information about the actual course of the CE event. Tapping common polymers and metal surfaces to each other and detecting the electrical potential produced on these surfaces 'in-situ' in individual events of contact and separation, we show that, charges are generated and transferred between the surfaces in both events; the measured potential is bipolar in contact and unipolar in separation. We show, the 'contact-charges' on the surfaces are indeed the net charges that results after the separation process, and a large contribution to tribocharge harvesting comes, in fact, from the electrostatic induction resulting from the generated CE charges. Our results refine the mechanism of CE providing information for rethinking the conventional ranking of materials' charging abilities, charge harvesting, and charge prevention.
Open Access
Chemical tracking of temperature by concurrent periodic precipitation pattern formation in polyacrylamide gels
(American Chemical Society, 2022-01-20) Khan, Muhammad Turab Ali; Kwiczak-Yiğitbaşı, Joanna; Tootoonchian, Pedram; Morsali, Mohammad; Lagzi, Istvan; Baytekin, Bilge
In nature, nonequilibrium systems reflect environmental changes, and these changes are often “recorded” in their solid body as they develop. Periodic precipitation patterns, aka Liesegang patterns (LPs), are visual sums of complex events in nonequilibrium reaction–diffusion processes. Here we aim to achieve an artificial system that “records” the temperature changes in the environment with the concurrent LP formation. We first illustrate the differences in 1-D LPs developing at different temperatures in terms of band spacings, which can demonstrate the time, ramp steepness, and extent of a temperature change. These results are discussed and augmented by a mathematical model. Using scanning electron microscopy, we show that the average size of the CuCrO4 precipitate also reflects the temperature changes. Finally, we show that these changes can also be “recorded” in the 2-D and 3-D LPs, which can have applications in long-term temperature tracking and complex soft material design.
Open Access
Complex patterning of matter with liesegang patterns propagating through different concentration media─gel lenses for liesegang waves
(American Chemical Society, 2023-11-18) Akbulut, Elif Sıla; Holló, Gábor; Lagzi, Istvan; Baytekin, Bilge
The patterns formed in natural biochemical and geochemical media are never spatially or geometrically homogeneous. On the other hand, the artificial systems trying to mimic nature are usually homogeneous and far from depicting the complexity of the natural ones. Liesegang patterns (LPs) are artificial reaction-diffusion precipitate patterns that can be formed in hydrogels. Although these patterns can be made to “sense” the environment, they are mostly formed in homogeneous media. Here, we present that a simple setting of different gel concentration boundaries can cause refractions of the pattern waves and changes in the band spacings. The extent of refraction is dependent on the macroscopic shape of the boundary. As imaged by scanning electron microscopy, the LP bands “crossing the boundaries” are formed by the product of a new morphology. This study can be a step forward in straightforwardly achieving complexity in artificial systems and developing new crystal forms of solids.
Open Access
Control of triboelectric charges on common polymers by photoexcitation of organic dyes
(Nature Publishing Group, 2019-01) Cezan, S. Doruk; Nalbant, Atakan A.; Büyüktemiz, M.; Dede, Y.; Baytekin, H. Tarık; Baytekin, Bilge
Triboelectric charging of insulators, also known as contact charging in which electrical charges develop on surfaces upon contact, is a significant problem that is especially critical for various industries such as polymers, pharmaceuticals, electronics, and space. Several methods of tribocharge mitigation exist in practice; however, none can reach the practicality of using light in the process. Here we show a light-controlled manipulation of triboelectric charges on common polymers, in which the tribocharges are mitigated upon illumination with appropriate wavelengths of light in presence of a mediator organic dye. Our method provides spatial and temporal control of mitigation of static charges on common polymer surfaces by a mechanism that involves photoexcitation of organic dyes, which also allows additional control using wavelength. This control over charge mitigation provides a way to manipulate macroscopic objects by tribocharging followed by light-controlled discharging.
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Core-shell quantum dot-embedded polymers for antistatic applications
(American Chemical Society, 2023-12-07) Ekim, Sunay Dilara; Aydın, Firdevs; Kaya, Görkem Eylül; Baytekin, H. Tarık; Asil, Demet; Baytekin, Bilge
Electrical charges develop on the surfaces of two insulator materials when they are in contact and separated. The retention of charges on insulator polymers causes material losses and hazards in industries using these polymers. Here, we show that a set of core-shell quantum dots embedded into a common polymer can destabilize the charges on the polymer. The locations of the charge carriers in the nanostructure, or the “type” of the dots, affect their discharging ability, which can also be manipulated or reverted remotely by light. The mechanism of antistatic action is presumed to contain interaction with polymer mechanospecies. The quantum dot embedding renders the polymers antistatic without changing their conductivity. Such antistatic additives, by which the polymers remain insulating, can be used to prevent static charges, e.g., in electronic coatings and in other antistatic applications.
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Design, fabrication, and locomotion analysis of an untethered miniature soft quadruped, SQuad
(IEEE, 2020) Kalın, Mert Ali İhsan; Aygül, Cem; Türkmen, Altay; Kwiczak-Yiğitbaşı, Joanna; Baytekin, Bilge; Özcan, Onur
The conventional robotics, which involves utilization of robots made out of hard materials like metals and hard plastics, has helped humankind automate many different sorts of labor and such robots have been assisting the humans in various tasks. Nevertheless, some applications require very delicate interactions and adaptability of the robots to unstructured elements and obstacles; which can only be provided by softness. The miniature and untethered robot in this work is fully made out of soft structural materials and uses a flexible circuit board. Only the electronic components, actuators and several little connection parts are hard. Its soft legs, body, and circuit enables it to overcome obstacles that conventional hard miniature robots tend to be stopped by. For the soft robot presented, walking and obstacle climbing experiments were done and pitch angle, roll angle, robot's centroid position and stiffness analyses were conducted. Additionally, three other robots are fabricated in hard body - hard leg, hard body - soft leg, and soft body - hard leg configurations and the effects of body and leg compliance on the locomotion performance are investigated. The results show that a soft body - soft leg robot configuration can scale an obstacle 1.44 times its body height whereas the hard bodied and hard legged robot can only go over 0.88 times its body height. The results also indicate that the softness of the body effects the scalable obstacle height more than the softness of the legs at this length scale.
Open Access
Effect of the polarity of solvents on periodic precipitation: Formation of hierarchical revert liesegang patterns
(American Chemical Society, 2022-10-11) Holló, Gábor; Zámbó, Dániel; Deák, András; Rossi, Federico; Rossi, Federico; Cucciniello, Raffaele; Nostro, Pierandrea Lo; Nabika, Hideki; Baytekin, Bilge; Lagz, István; Itatani, Masaki
Liesegang pattern (LP) is one example of self-organized periodic precipitation patterns in nonequilibrium systems. Several studies have demonstrated that the LP morphology can track physicochemical environmental conditions (e.g., temperature); however, the polarity effect has not been explored to date. In this study, a copper chromate system is used to reveal the impact of solvent polarity on the evolving LP structure using water/organic solvent mixtures. In the typical case of using water/dimethyl sulfoxide (DMSO) mixtures, two drastic changes in LP morphology with increasing DMSO contents were found: (i) increasing frequency of the original structure and (ii) formation of a hierarchical pattern with the appearance of another, lower-frequency structure. Furthermore, the simulation model operating with a bimodal size distribution, allowing both homogeneous and heterogeneous precipitations showed good agreement with the experimental results. Therefore, this study demonstrated that LP can be tailored by solvent polarity and can be used for designing hierarchical precipitation patterns in a straightforward manner.
Open Access
Joint design and fabrication for multi-material soft/hybrid robots
(IEEE, 2019-04) Aygül, Cern; Kwiczak-Yiğitbaşı, Joanna; Baytekin, Bilge; Özcan, Onur
The premises of safer interactions with surroundings and the higher adaptability to its environment make soft robotics a very interesting research field. Some robots try to achieve these feats using soft materials in their designs whereas some achieve behavioral softness through compliant use of hard materials. In this work, we present soft/hybrid robot leg designs that utilize elastomers as leg materials but hard DC motors as actuators. Two different leg designs that would convert the rotational motion of the DC motors to a foot trajectory are proposed. The different leg designs are kinematically identical; however, the hourglass design utilizes geometrical modifications to differentiate joint locations, whereas the composite design uses materials with different Young's Moduli without geometrical effects to create joints. In order to fabricate the composite design, a new method is developed involving 3D printed molds with removable joint pieces and a two-step molding process. Both of the legs are fabricated and simulations and experiments are run to compare their performances. Both mechanisms achieve a good foot trajectory, however the hourglass joint experiences higher mechanical stress during operation, which might lead to earlier failure especially under high loads. Such multi-material structures made out of elastomers can be utilized in miniature robots or mechanisms of similar size in which absolute joint locations are needed and continuum robotic limbs are not preferred.
Open Access
Mechanical control of periodic precipitation in stretchable gels to retrieve information on slastic deformation and for the complex patterning of matter
(Wiley-VCH Verlag, 2020-03) Morsali, Mohammad; Khan, Muhammad Turab Ali; Ashirov, Rahym; Holló, G.; Baytekin, H. Tarık; Lagzi, I.; Baytekin, Bilge
Material design using nonequilibrium systems provides straightforward access to complexity levels that are possible through dynamic processes. Pattern formation through nonequilibrium processes and reaction–diffusion can be used to achieve this goal. Liesegang patterns (LPs) are a kind of periodic precipitation patterns formed through reaction–diffusion. So far, it has been shown that the periodic band structure of LPs and the geometry of the pattern can be controlled by experimental conditions and external fields (e.g., electrical or magnetic). However, there are no examples of these systems being used to retrieve information about the changes in the environment as they form, and there are no studies making use of these patterns for complex material preparation. This work shows the formation of LPs by a diffusion–precipitation reaction in a stretchable hydrogel and the control of the obtained patterns by the unprecedented and uncommon method of mechanical input. Additionally, how to use this protocol and how deviations from “LP behavior” of the patterns can be used to “write and store” information about the time, duration, extent, and direction of gel deformation are presented. Finally, an example of using complex patterning to deposit polypyrrole by using precipitation patterns is shown as a template.
Open Access
Mechanochemical generation of singlet oxygen
(Royal Society of Chemistry, 2020) Türksoy, Abdurrahman; Yıldız, Deniz; Aydonat, Simay; Bedük, Tutku; Canyurt, Merve; Baytekin, Bilge; Akkaya, E. U.
Controlled generation of singlet oxygen is very important due to its involvement in scheduled cellular maintenance processes and therapeutic potential. As a consequence, precise manipulation of singlet oxygen release rates under mild conditions, is crucial. In this work, a cross-linked polyacrylate, and a polydimethylsiloxane elastomer incorporating anthracene-endoperoxide modules with chain extensions at the 9,10-positions were synthesized. We now report that on mechanical agitation in cryogenic ball mill, fluorescence emission due to anthracene units in the PMA (polymethacrylate) polymer is enhanced, with a concomitant generation of singlet oxygen as proved by detection with a selective probe. The PDMS (polydimethylsiloxane) elastomer with the anthracene endoperoxide mechanophore, is also similarly sensitive to mechanical force.
Open Access
Minimizing friction, wear, and energy losses by eliminating contact charging
(American Association for the Advancement of Science, 2018) Sayfidinov, K.; Cezan, S. D.; Baytekin, Bilge; Baytekin, H. T.
One-fourth of the global energy losses result from friction and wear. Although friction and tribocharging were presented to be mutually related, reduction of friction and wear by eliminating tribocharges on common polymers, and decrease of power losses in devices with polymer parts were not shown to date. Here, we demonstrate that for common polymers, friction—which is strongly related to surface charge density—can be notably reduced by various methods of tribocharge mitigation, namely, corona discharging, solvent treatment, or placing a grounded conductor on the backside of one of the shearing materials. In our simple demonstrations, we found that by preventing tribocharge accumulation, a remarkable two-thirds of power loss during operation of simple mechanical devices with common polymers and plastic parts can be saved and wear can be reduced by a factor of 10. These demonstrations indicate important practical ramifications in mechanical systems with insulating parts. Copyright
Open Access
Molecular design of lignin-derived side-chain phenolic polymers toward functional radical scavenging materials with antioxidant and antistatic properties
(ACS Publications, 2023-05-11) Rubens, M.; Falireas, P.; Vanbroekhoven, K.; Van Hecke, W.; Kaya, Görkem Eylül; Baytekin, Bilge; Vendamme, R.
This article reports a new family of functional side-chain phenolic polymers derived from lignin monomers, displaying a combination of properties that are usually mutually exclusive within a single material. This includes a well-defined molecular structure, transparency, antioxidant activity, and antistatic properties. Our design strategy is based on the lignin-derived bioaromatic monomer dihydroconiferyl alcohol (DCA), a promising and yet largely unexplored asymmetrical diol bearing one aliphatic and one phenolic hydroxyl group. A lipase-catalyzed (meth)acrylation protocol was developed to selectively functionalize the aliphatic hydroxy group of DCA while preserving its phenolic group responsible for its radical scavenging properties. The resulting mono-(meth)acrylated monomers were then directly copolymerized using reversible addition-fragmentation chain-transfer (RAFT) polymerization without any protection of the phenolic side chains. Kinetics studies revealed that, under select conditions, these unprotected phenolic groups surprisingly did not inhibit the radical polymerization and lead to polymers with defined molar masses, low dispersities, and block copolymers. Finally, applications of these new radical scavenging polymers were demonstrated using an antioxidant assay and antistatic experiments. This research opens the door to the direct incorporation of natural antioxidants within the synthetic polymer backbones, increasing the biobased content and limiting the leaching of potentially harmful additives.
Open Access
The morphological changes upon cryomilling of cellulose and concurrent generation of mechanoradicals
(Elsevier, 2019) Laçin, Özge; Kwiczak-Yiğitbaşı, Joanna; Erkan, Meltem; Cevher, Ş. C.; Baytekin, Bilge
With mechanical input, chemical bonds in polymers can be broken. Recently, it was shown that reactive ends formed by homolytic cleavage, so-called mechanoradicals, can be used in driving further chemical reactions or in making new composite materials. Cellulose, the most abundant polymer on earth, can also be subjected to mechanical input via ball-milling to produce mechanoradicals. Despite many reports on morphological changes in cellulose upon milling, there is only a limited understanding on how these changes affect the mechanoradical production, i.e., in which domains of cellulose the bonds are broken to produce the mechanoradicals. Here we show, the effect of the initial morphology of cellulose (cotton or microcrystalline cellulose) and the mode of grinding (dry or solvent-assisted) on the amount of generated cellulose mechanoradicals. The morphological and the chemical changes taking place upon milling of cellulose are monitored by SEM, XRD, and ATR, and the number of mechanoradicals is determined by a first-time quantitative analysis of cellulose mechanoradicals using radical scavenger DPPH. Our findings can help in efficient mechanofunctionalization of cellulose and to make useful mechanochemical reactions of cellulose using mechanoradicals, which stand as a promising economic and environment-friendly alternative to the conventional solvent-assisted chemistry of cellulose.
Open Access
Online lubricant degradation monitoring using contact charging of polymers
(Elsevier, 2022-05-15) Baytekin, Bilge; Baytekin, H. T.; Karluk, Azimet Akber; Ekim, Sunay Dilara
Lubrication of machine parts is necessary to prevent friction and wear in machine operation. However, oxidation of lubricants upon operation changes their chemical and physical properties and causes lubrication performance to deteriorate. Besides, one liter of wasted/used lubricant oil can contaminate a million liters of water. Current methods for the timely detection of oil deterioration lack practicality. Here we show simple, a triboelectrification-based method for oil degradation monitoring, in which the oxidation can be monitored by the changes in the contact charging (and separation) signals of oil-dipped cellulose and a common polymer tapped to each other. The commercial and base oil samples are oxidized at 100–200 °C for up to 80 h, simultaneously monitored by ATR-FTIR and the triboelectric method. The results show that a 40–90% decrease in the triboelectric open-circuit potentials in the presence of oxidized oil can directly indicate the start of oil oxidation without other accompanying analyses.
Open Access
Organic charge transfer cocrystals as additives for dissipation of contact charges on polymers
(American Chemical Society, 2022-12-06) Ekim, Sunay Dilara; Kaya, Görkem Eylül; Daştemir, M.; Yildirim, E.; Baytekin, H. T.; Baytekin, Bilge
Common polymers can accumulate surface charges through contact, a phenomenon known since ancient times. This charge accumulation can have detrimental consequences in industry. It causes accidents and yields enormous economic losses. Many empirical methods have been developed to prevent the problems caused by charge accumulation. However, a general chemical approach is still missing in the literature since the charge accumulation and discharging mechanisms have not been completely clarified. The current practice to achieve charge mitigation is to increase materials conductivity by high doping of conductive additives. A recent study showed that using photoexcitation of some organic dyes, charge decay can be started remotely, and the minute amount of additive does not change the material's conductivity. Here, we show the contact charging and charge decay behavior of polydimethylsiloxane doped with a series of organic charge transfer cocrystals (CTC) of TCNQ acceptor and substituted pyrene donors (CTC-PDMS). The results show that the CTC-PDMS are antistatic, and the discharging propensity of the composites follows the calculated charge transfer degree of the complexes. On the other hand, the CTC-PDMS are still insulators, as shown by their high surface resistivities. Kelvin probe force microscopy images of the contact-charged and discharged samples show a quick potential decay in CTC domains upon illumination. Combined with the fast overall decay observed, the antistatic behavior in these insulators can be attributed to an electron transfer between the mechanoions in the polymer and the CTC frontier orbitals. We believe our results will help with the general understanding of the molecular mechanism of contact charging and discharging and help develop insulator antistatics.
Open Access
Self-regulating plant robots: bioinspired heliotropism and nyctinasty
(Mary Ann Liebert, 2020) Cezan, Süleyman Doruk; Baytekin, Hasan Tarık; Baytekin, Bilge
Self-regulation (or so-called homeostasis) is a property of all living organisms to maintain an internal stable state through specialized biofeedback mechanisms under varying external and internal conditions. Although these feedback mechanisms in living organisms are complex networks and hard to implement one-to-one in artificial systems, the new approaches in soft robotics may benefit from the concept of self-regulation—especially in the new endeavors of making untethered, autonomous soft robots. In this study, we show a simple system, in which plant robots display heliotropism (sun tracking) and nyctinasty (leaf opening) through artificial self-regulation attained through a bioinspired transpiration mechanism. The feedback involves dehydration/hydration and transpiration events that keep the stem continuously in a metastable position, which maximizes light on plant leaves and the efficiency of light harvesting when solar panels are attached on leaves. We also demonstrate that this artificial feedback can be regulated by doping with light-absorbing chemicals or by changing the geometry of the system, and it can further be expanded to other lightweight systems. Implementing self-regulation into (soft) robots through bioinspired material feedback is beneficial not only for energy efficiency and harvesting but also for achieving embodied intelligence in autonomous soft robots.