PUBLICATIONS
Stanford Affiliated Publications
16. Guide for Nanomechanical Characterization of Soft Matter via AFM: from Mode Selection to Data Reporting
E. Kim, A.L. Ramos Figueroa, M. Schrock, E. Zhang, C. Newcomb, Z. Bao, L. Michalek* - submitted
This primer provides a practical framework for conducting reproducible nanomechanical measurements on soft materials using AFM, covering four key aspects: measurement mode selection, probe choice, calibration procedures, and data analysis methods. The guide aims to standardize AFM measurement protocols across different laboratories by addressing common challenges in reproducibility and offering detailed best practices for researchers, from novices to experts, working with soft matter characterization at the nanoscale.
15. Electrochemical Formation of Bis(fluorosulfonyl)imide-derived Solid-Electrolyte Interphase at Li-metal Potential
W. Yu, K‐Y. Lin, D.T. Boyle, M.T. Tang, Y. Cui, Y. Chen, Z. Yu, R. Xu, Y. Lin, G. Feng, Z. Huang, L. Michalek, W. Li, S.J. Harris, J-C. Jiang, F. Abild-Pedersen, J. Qin, Y. Cui, Z. Bao* - Nature Chemistry
We explore the formation mechanism of the solid-electrolyte interphase (SEI) layer in lithium metal batteries using lithium bis(fluorosulfonyl)imide-based electrolytes, combining electrochemical analysis and X-ray photoelectron spectroscopy. We found that high-performance electrolytes can form an effective passivation layer with minimal electrolyte decomposition by incorporating more anion-derived products, providing insights for designing better battery electrolytes.
14. A Transparent, Patternable, and Stretchable Conducting Polymer Solid Electrode for Dielectric Elastomer Actuators
E. Kim, J‐C. Lai, L. Michalek, W. Wang, C. Xu, H. Lyu, W. Yu, H. Park, Y. Tomo, S.E. Root, B. Lee, J. Park, B. Park, S. Wei, C. Zhao, Z. Bao* - Advanced Functional Materials
We introduced a novel transparent and stretchable conducting polymer electrode made of PEDOT:PSS and P123DA for use in dielectric elastomer actuators, achieving over 95% optical transmittance and actuation performance comparable to carbon grease. By optimizing the ratio of P123DA to PEDOT:PSS, we were able to tune the electrical and mechanical properties to create a solid electrode that enables both static and dynamic actuation while maintaining patternability and transparency, making it suitable for applications in haptics, soft robotics, and smart lenses.
13. Printable, Stretchable Metal-vapor-desorption Layers for High-fidelity Patterning in Soft, Freeform Electronics
S. Jeong, H. Yoon, L. Michalek, G. Kim, J. Kim, J. Seo, D. Kim, H. Park, B. Lee, Y. Hong* -
Nature Communications
A breakthrough in flexible electronics enables high-fidelity patterning of thin metal films through printable, stretchable metal-vapor-desorption layers (s-MVDLs) that effectively repel metal vapors during deposition. This new approach allows selective metal patterning from microscale to millimeter scale with applications in wearable electronics, sensors, and displays on curved and flexible surfaces.
12. Shape-memory-assisted Self-healing of Macroscopic Punctures via High Energy Density Periodic Dynamic Polymers with Tunable Actuation Temperature
Y. Shi, C. B. Cooper, T. Nogusa, J-C. Lai, H. Lyu, M. Khatib, C. Xu, L. Michalek, Z. Bao* - Matter
We introduce a new type of shape memory polymer that combines strong and weak hydrogen bonding units to enable both high energy density shape memory behavior and self-healing capabilities at accessible temperatures. These polymers can heal large punctures through a two-step process where the high energy density first enables autonomous closure of damaged areas followed by diffusive self-healing to repair the interface, representing a significant advance over previous self-healing shape memory polymers that could only heal submillimeter damage.
11. Tuning Polymer-backbone Coplanarity and Conformational Order to Achieve High-performance Printed All-polymer Solar Cells
Y. Wu, Y. Yuan, D. Sorbelli, C. Cheng, L. Michalek, H-W. Cheng, V. Jindal, S. Zhang, G. LeCroy, E. D. Gomez, S. T. Milner, A. Salleo, G. Galli, J. B. Asbury, M. F. Toney, Z. Bao* - Nature Communications
A new polymer acceptor design with bithiazole linker (PY-BTz) has achieved 16.4% efficiency in all-polymer solar cells by enabling better backbone coplanarity and conformational order compared to conventional thiophene-based linkers. The improved performance comes from enhanced conjugation along the polymer backbone and closer interchain π-stacking, leading to higher charge mobilities and reduced recombination losses, with the design also demonstrating 14.7% efficiency when solution-sheared under ambient conditions.
10. Tuning the Mobility of Indacenodithiophene-Based Conjugated Polymers via Coplanar Backbone Engineering
X. Ji, H.-W. Cheng, N.J. Schuster, G.S. LeCroy, S. Zhang, Y. Wu, L. Michalek, B.-N.T. Nguyen, J.A. Chong, M. Schrock, Y. Tomo. J. Rech, A. Salleo, S. Gam, G.H. Lee, J. B-H. Tok, Z. Bao* - Chemistry of Materials
We introduce structural modifications to indacenodithiophene-benzothiadiazole (IDT-BT) polymers aimed at improving charge carrier mobility while maintaining low crystallinity through backbone engineering and noncovalent interactions. The fluorinated derivative IDT-FBT achieved the highest mobility of 5.19 cm²/(V·s), attributed to enhanced backbone planarity through S···F and H···F noncovalent interactions and improved interchain interactions via strong aggregation.
9. Sequence-dependent Self-assembly of Supramolecular Nanofibers in Periodic Dynamic Block Copolymers
J.K. Phong, C.B. Cooper, L. Michalek, Y. Lin, Y. Nishio, Y. Shi, H. Gong, J.A. Vigil, J. Ilavsky, I. Kuzmenko, Z. Bao* - Journal of Materials Chemistry A
Dynamic block copolymers with periodic sequences self-assemble into high aspect ratio supramolecular nanofibers with well-ordered PEG and PDMS domains, while random sequences form disordered morphologies. The periodic nanofibers exhibit superior properties including delayed terminal flow by up to 60°C and ionic conductivity values over two orders of magnitude higher than random counterparts due to the formation of well-ordered, interconnected ion-transporting domains.
8. Degradable Semiconducting Polymers without Long-Range Order for On-demand Degradation of Transient Electronics
J.A. Chiong, L. Michalek, A. Peña-Alcántara, X. Ji, N.J. Shuster, Z. Bao* - Journal of Materials Chemistry C
We present a new class of degradable semiconducting polymers based on indacenodithiophene units that lack long-range order, demonstrating enhanced stretchability while maintaining electronic performance similar to their semicrystalline counterparts. We show that these polymers can degrade orders of magnitude faster than conventional semiconducting polymers and under milder acidic conditions that better resemble biological environments.
7. Tunable 1D and 2D Polyacrylonitrile Nanosheet Superstructures
H. Gong, D.U. Patino, J. Ilavsky, I. Kuzmenko, A. Peña-Alcántara, C. Zhu, A.H. Coffey, L. Michalek, A. Elabd, X. Gao, S. Chen, C. Xu, H. Yan, Y. Jiang, W. Wang, Y. Peng, Y. Zeng, H. Lyu, H. Moon, Z. Bao* - ACS Nano
We developed a method to synthesize hierarchical polyacrylonitrile (PAN) nanostructures by controlling PAN's nucleation and growth behavior. These nanostructured PAN materials can be converted into carbon superstructures for applications like superhydrophobic surfaces.
6. Genetically targeted chemical assembly of polymers specifically localized extracellularly to surface membranes of living neurons
A. Zhang, K.Y. Loh, C.S Kadur, L. Michalek, J. Dou, C. Ramakrishnan, Z. Bao*, K. Deisseroth* - Science Advances
A new genetic engineering method enables localized enzyme expression on neuronal membranes, allowing in situ polymerization of diverse materials precisely on target cells to create biocompatible interfaces between engineered structures and living neural networks. This platform may enable minimally invasive cell-specific biointerfaces for neural tissues.
5. Environmentally stable and stretchable polymer electronics enabled by surface-tethered nanostructured molecular-level protection
Y. Zheng, L. Michalek, Q. Liu, Y. Wu, H. Kim, P. Sayavong, W. Yu, D. Zhong, C. Zhao, Z. Yu, J.A. Chiong, H. Gong, X. Ji, D. Liu, S. Zhang, N. Prine, Z. Zhang, W. Wang, J.B.-H. Tok, X. Gu, Y. Cui, J. Kang, Z. Bao* - Nature Nanotechnology
The surface-tethered nanostructured fluorinated molecular protection layer enables highly stable stretchable polymer semiconductors operable in direct contact with physiological environments for extended periods. This molecular approach outperforms thicker polymer encapsulants for environmental protection of soft stretchable electronics.
4. Autonomous alignment and healing in multilayer soft electronics using immiscible dynamic polymers
C.B Cooper, S.E. Root, L. Michalek, S. Wu, J.-C. Lai, M. Khatib, S.T. Oyakhire, R. Zhao, J. Qin, Z Bao* - Science
By using two dynamic polymers with identical bonds but immiscible backbones, we created soft electronics and robots that can autonomously realign and restore functionality when damaged, mimicking the self-healing properties of human skin. This materials innovation enables devices like pressure sensors, soft robots, and circuits to heal themselves after damage.
3. Effect of Molecular Weight on the Morphology of a Polymer Semiconductor–Thermoplastic Elastomer Blend
A. Peña‐Alcántara, S. Nikzad, L. Michalek, N. Prine, Y. Wang, H. Gong, E. Ponte, S. Schneider, Y. Wu, S.E. Root, M. He, J.B‐H Tok, X. Gu*, Z. Bao* - Advanced Electronic Materials
Blending the polymer semiconductor P2TDPP2TFT4 with the elastomer SEBS greatly increased fracture strain, and tuning the molecular weights of both components optimized the blend's morphology, electrical properties, and mechanics for high-performance stretchable electronics.
2. Shear-aligned large-area organic semiconductor crystals through extended π–π interaction
S. Zhang, F. Talnack, T. Jousselin-Oba, V. Bhat, Y. Wu, Y. Lei, Y. Tomo, H. Gong, L. Michalek, D. Zhong, C. Wu, A. Yassar, S. Mannsfeld*, C. Risko*, M. Frigoli*, Z. Bao* -
Journal of Materials Chemistry C
We grew large, oriented TIPS-PPP crystals using solution shear coating, achieving high hole mobilities up to 6.5 cm2/V-s along the preferred packing direction - among the highest reported for pentacene derivatives and enabled by TIPS-PPP's enhanced molecular ordering and thermal stability compared to related organic semiconductors. This work reveals the structure-property relationships in TIPS-PPP through control over crystallite size and orientation.
1. Realizing intrinsically stretchable semiconducting polymer films by nontoxic additives
H.-W. Cheng, S. Zhang, L. Michalek, X. Ji, S. Luo, C.B. Cooper, H. Gong, S. Nikzad, J.A Chiong, Y. Wu, Y. Zheng, Q. Liu, D. Zhong, Y. Lei, Y. Tomo, K.-H. Wei, D. Zhou, J.B.-H. Tok,
Z. Bao* - ACS Materials Letters
The nontoxic small molecule triacetin (TA) added as a plasticizing additive preserves charge mobility in stretchable semiconducting polymer films by reducing polymer chain aggregation and crystallinity, enabling soft electronics that maintain performance even after repeated high strains. TA incorporation allows high-mobility semiconducting polymers to achieve both stretchability and strain-independent charge transport.
Queensland University of Technology (QUT) Affiliated Publications
20. Photolyzable Polymer Brushes: Subtractive 3D Structuring of Surfaces using Water and Light
H. Kalmer, P.T. Do, F. Sbordone, K. Mundsinger, R.T. Jones, D. Harkin, T. Dargaville, J. Mendhi, L. Michalek, A. Nelson*, H. Frisch* - submitted
This research introduces a new method for modifying polymer brushes on surfaces using just water and light, where specific parts of the coating can be selectively broken down to create precise 3D patterns. The technique allows to first create a uniform coating and then sculpt it later as needed, while maintaining the coating's original properties like water resistance and cell interaction, which could be valuable for various applications in medicine and materials science.
19. A Bioinspired Approach to Reversibly Metal Binding Interfaces
A.C. Morrissey, V. Jayalatharachchi, L. Michalek, P. Egodawatta, N. Zaquen, L. Delafresnaye*, C. Barner-Kowollik* - RCS Applied Polymers
We introduced a bioinspired coating material based on modified L-DOPA that can effectively bind and release metal ions like zinc, copper, and lead from surfaces. We demonstrated that by incorporating a terpyridine ligand into the L-DOPA structure, the coating can both strongly adhere to various surfaces (including silicon wafers and stone wool fibers) and reversibly capture metal ions using EDTA as an extracting agent, making it promising for applications in water treatment and pollution control.
18. A Versatile Light‐Triggered Radical‐Releasing Surface Coating Technology
N.R.B Boase, L. Michalek, J.P. Hooker, K. E. Fairfull‐Smith* -
Advanced Materials Technologies
A new light-responsive organic redox coating that releases radicals when irradiated with UV light was developed, demonstrating versatile potential applications including microparticle pollution sensors, switchable electrodes, and anti-biofouling medical coatings. This innovation overcomes prior challenges with substrate versatility and responsiveness for organic redox materials.
17. Light‐Gated Control of Conformational Changes in Polymer Brushes
S. Bialas, T. Krappitz, S.L. Walden, K. Kalayci, D. Kodura, H. Frisch, J.M. MacLeod, A. Nelson*, L. Michalek*, C Barner‐Kowollik* - Advanced Materials Technologies
We designed a photoreactive polymer brushes on surfaces that can undergo controlled conformational changes upon exposure to light, enabling precise spatiotemporal manipulation of the brush structure and properties through photo-triggered crosslinking. Wavelength-selective crosslinking of multifunctional brush structures allows specific sections to be crosslinked based on irradiation wavelength.
16. Photostationary State in Dynamic Covalent Networks
L.C. Chambers, C. Barner-Kowollik, L. Barner, L. Michalek*, H. Frisch* - ACS Macro Letters
A visible light-cured polymer network based on styrylpyrene photochemistry can be selectively decoupled with UV irradiation, but the proximity of the reactive groups limits the extent of decoupling to retain mechanical integrity. Applying an additional stimulus may help overcome this proximity effect to induce further network disintegration with UV light.
15. A versatile and straightforward process to turn plastics into antibacterial materials
S. Hadiouch, M. Maresca, D. Gigmes, G. Machado, A. Maurel-Pantel, S. Frik, J. Saunier, A. Deniset-Besseau, N. Yagoubi, L. Michalek, C. Barner-Kowollik, Y. Guillaneuf, C. Lefay* - Polymer Chemistry
Common plastics can be made antibacterial by incorporating specifically designed amphiphilic cationic methacrylate copolymers, providing a simple, low-cost approach to create antibacterial materials for applications like packaging and medical devices without changing production methods or sacrificing mechanical properties. The copolymers confer antibacterial activity by targeting the bacterial membrane, avoiding toxicity to human cells.
14. Chain-Length-Dependent Photolysis of ortho-Nitrobenzyl-Centered Polymers
J. Bachmann, C. Petit, L. Michalek, Y. Catel, E. Blasco, J.P. Blinco*, A.-N. Unterreiner*, C. Barner-Kowollik* - ACS Macro Letters
We demonstrated that the rate of photochemical cleavage of linear polymers containing a midchain photocleavable unit has a strong nonlinear dependence on polymer chain length, which has important implications for designing photocleavable polymer networks. The increase in cleavage rate with molecular weight is attributed to entropic effects.
13. UV-induced photolysis of polyurethanes
C. Petit, J. Bachmann, L. Michalek, Y. Catel, E. Blasco, J.P. Blinco*, A.-N. Unterreiner*, C. Barner-Kowollik* - Chemical Communications
Polyurethanes (PUs) are widely used in packaging but their lack of degradability causes environmental waste; incorporating photosensitive units into PUs allows for controllable photodegradation, offering a potential solution to make PUs more sustainable.
12. Mapping photochemical reactivity profiles on surfaces
L. Michalek, T. Krappitz, K. Mundsinger, S.L. Walden, L. Barner, C. Barner-Kowollik* - https://onlinelibrary.wiley.com/doi/abs/10.1002/adma.201807288
Journal of the American Chemical Society
The reactivity of photochemical groups attached to surfaces was mapped to their surface absorption spectra, finding that unlike in solution, surface reactivity closely mirrors absorption with no red-shifting. This allows systematic relating of surface absorption to photoreactivity for the first time.
11. Two Grapes Short of a Fruit Salad: Raspberry-, Strawberry-, and Seedpod-Like Organic Microspheres via Colloidal Nanotemplating
K. Mundsinger, C.W. Schmitt, L. Michalek, M. Susewind, T. Hofe, C. Barner-Kowollik*, L. Barner* - ACS Macro Letters
We developed a modular method to synthesize organic-inorganic particles with unique raspberry, strawberry, and seedpod-like surface morphologies by attaching silica nanoparticle templates and polymer shells to divinylbenzene cores and then removing the templates. The resulting superficially porous particles were analyzed for their morphology and surface chemistry using microscopy and spectroscopy techniques.
10. 2D fabrication of tunable responsive interpenetrating polymer networks from a single photoresist
L. Michalek, S. Bialas, S.L. Walden, F.R. Bloesser, H. Frisch*, C. Barner‐Kowollik* -
Advanced Functional Materials
Photocuring of blended polymers with different photoreactive groups enables spatial control over interpenetrating polymer network formation to precisely tune material properties like swelling behavior. This light-gated IPN formation method allows property adjustments within a single polymer blend through incorporation of secondary networks in specific regions.
9. Wavelength‐Selective Folding of Single Polymer Chains with Different Colors of Visible Light
H. Frisch, D. Kodura, F.R. Bloesser, L. Michalek, C. Barner‐Kowollik* -
Macromolecular Rapid Communications
Photochemistry enables precise spatiotemporal control over polymer crosslinking by using different wavelengths of visible light to selectively trigger different cycloaddition reactions that dictate the degree of intramolecular crosslinking. This allows remote, stepwise control over mechanical properties at the molecular level.
8. Adaptable and reprogrammable surfaces
A.S. Goldmann*, N.R.B Boase, L. Michalek, J.P. Blinco, A. Welle, C. Barner‐Kowollik* - Advanced Materials
Reversible surface chemistries enable precise, adaptable functionalization of material interfaces, but still face limitations in synthesis, characterization, and integration that must be overcome to fully realize their potential for reprogrammable, functional interfaces. Spatial and temporal control of light-induced reversible reactions shows particular promise when combined with laser lithography.
7. Quantifying solvent effects on polymer surface grafting
L. Michalek, K. Mundsinger, L. Barner*, C. Barner-Kowollik* -
ACS Macro Letters
The use of a poor solvent leads to preferential grafting of shorter polymer chains onto surfaces, altering the molecular weight distribution compared to in solution and affecting the resulting interface properties and their determination. The solvent conditions are thus critical in controlling grafting polymer interface properties.
6. Access to disparate soft matter materials by curing with two colors of light
S. Bialas, L. Michalek, D.E. Marschner, T. Krappitz, M. Wegener, J. Blinco*, E. Blasco*, H. Frisch*, C. Barner‐Kowollik* - Advanced Materials
This photoresist technology uses orthogonal light wavelengths to selectively crosslink different components, enabling multimaterial 3D printing and coatings through wavelength-orthogonal control of photochemistry. The innovation is achieving wavelength orthogonality so each wavelength only activates its specific target within the resist mixture.
5. The long and the short of polymer grafting
L. Michalek, K. Mundsinger, C. Barner-Kowollik*, L. Barner* -
Polymer Chemistry
The grafting of polymer chains to an interface distorts the chain length distribution, favoring attachment of shorter chains, which is quantified for the first time with a new preferential grafting factor. This effect has critical implications for polymer interface design and analysis methods.
4. Polyselenoureas via multicomponent polymerizations using elemental selenium as monomer
B.T. Tuten*, F.R. Bloesser, D.L. Marshall, L. Michalek, C.W. Schmitt, S.J. Blanksby, C. Barner-Kowollik* - ACS Macro Letters
Multicomponent polymerizations provide a simple, mild method to synthesize polyselenoureas, a new class of polymers containing selenium in the backbone that enables detailed characterization through distinct spectroscopic signatures. The commercially available monomers and ambient temperature conditions make this facile synthesis broadly applicable.
3. A Subtractive Photoresist Platform for Micro‐and Macroscopic 3D Printed Structures
M.M. Zieger, P. Müller, E. Blasco*, C. Petit, V. Hahn, L. Michalek, H. Mutlu, M. Wegener*, C. Barner‐Kowollik* - Advanced Functional Materials
We introduce a versatile, subtractive photoresist platform that enables easy removal of micro and macro scale 3D printed structures, allowing construction of more complex geometries; the analysis techniques and example application demonstrate the capabilities of this innovative platform.
2. Polymer on top: Current limits and future perspectives of quantitatively evaluating surface grafting
L. Michalek, L. Barner*, C. Barner‐Kowollik* - Advanced Materials
A practical access guide for comparatively and quantitatively evaluating the reliability of a given approach is provided, enabling the field to critically judge experimentally determined grafting densities and to avoid the reporting of grafting densities that fall outside the physically realistic parameter space. The assessment is concluded with a perspective on the development of advanced approaches for determination of grafting density, in particular, on single-chain methodologies.
1. Engineering nitroxide functional surfaces using bioinspired adhesion
H. Woehlk, J. Steinkoenig, C. Lang, L. Michalek, V. Trouillet, P. Krolla, A.S. Goldmann, L. Barner, J.P. Blinco, C. Barner-Kowollik*, K.E. Fairfull-Smith* - Langmuir
We developed a mussel-inspired method to coat various materials with thin polymer films containing redox-active nitroxide radicals, which may enable applications in electronics such as organic radical batteries. The films were synthesized via oxidative polymerization of a catecholamine monomer modified with a TEMPO nitroxide group.
University of Stuttgart Affiliated Publications
3. The role of surface oxides on hydrogen sorption kinetics in titanium thin films
E. Hadjixenophontos*, L. Michalek, M. Roussel, M. Hirscher, G. Schmitz -
Applied Surface Science
Titanium thin films are used as a model system to study the atomic-scale diffusion and kinetics of hydrogenation, finding that hydrogen transport through the native titanium oxide layer is the rate-limiting step in the overall absorption process. Quantitative diffusion coefficients for hydrogen in both the oxide layer and metallic titanium are obtained through pressure-dependent measurements and modeling.
2. Hydrogen Sorption Kinetics in MgH2 and TiH2 Thin Films
E. Hadjixenophontos*, L. Michalek, A. Weigel, G. Schmitz - Defect and Diffusion Forum
Thin films of Mg and Ti are used to study H diffusion in metals at high pressures, finding linear kinetics at 200°C in Mg, parabolic at 300°C, while in Ti the oxide layer causes linear kinetics and the hydride forms from the substrate inward unlike Mg. Quantitative calculations determine the H diffusion rates and growth kinetics in the metal hydrides.
1. A Monolithic Hybrid Cellulose‐2.5‐Acetate/Polymer Bioreactor for Biocatalysis under Continuous Liquid–Liquid Conditions Using a Supported Ionic Liquid Phase
B. Sandig, L. Michalek, S. Vlahovic, M. Antonovici, B. Hauer, M.R. Buchmeiser* -
Chemistry–A European Journal
Mesoporous monolithic hybrid cellulose-acetate/polymer supports were synthesized and used as bioreactors for continuous enzymatic transesterification reactions, achieving high conversion and turnover number over 18 days due to the immobilized ionic liquid-lipase system. This liquid-liquid setup with a hybrid reactor shows promise for enhancing productivity of other enzymatic reactions.