Professional Education


  • Master of Science, Institut National Polytechnique (2011)
  • Doctor of Philosophy, Royal Institute of Technology (2015)

Stanford Advisors


  • Yi Cui, Postdoctoral Faculty Sponsor

All Publications


  • Nanometer-Thick Hyaluronic Acid Self-Assemblies with Strong Adhesive Properties ACS APPLIED MATERIALS & INTERFACES Marais, A., Pendergraph, S., Wagberg, L. 2015; 7 (28): 15143-15147

    Abstract

    The adhesive characteristics of poly(allylamine hydrochloride) (PAH)/hyaluronic acid (HA) self-assemblies were investigated using contact adhesion testing. Poly(dimethylsiloxane) spheres and silicon wafers were coated with layer-by-layer (LbL) assemblies of PAH/HA. No increase in adhesion was observed when surfaces covered with dried LbL films were placed in contact. However, bringing the coated surfaces in contact while wet and separating them after drying resulted in an increase by a factor of 100 in the work of adhesion (from one to three bilayers). Herein we discuss the adhesion in PAH/HA and PAH/poly(acrylic acid) assemblies. PAH/HA assemblies have potential application as strong biomedical adhesives.

    View details for DOI 10.1021/acsami.5b03760

    View details for Web of Science ID 000358558300005

    View details for PubMedID 26151110

  • Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries NATURE COMMUNICATIONS Nystrom, G., Marais, A., Karabulut, E., Wagberg, L., Cui, Y., Hamedi, M. M. 2015; 6

    Abstract

    Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g(-1) and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices.

    View details for DOI 10.1038/ncomms8259

    View details for Web of Science ID 000355539700001

    View details for PubMedID 26021485

  • Robust and Tailored Wet Adhesion in Biopolymer Thin Films BIOMACROMOLECULES Pettersson, T., Pendergraph, S. A., Utsel, S., Marais, A., Gustafsson, E., Wagberg, L. 2014; 15 (12): 4420-4428

    Abstract

    Model layer-by-layer (LbL) assemblies of poly(allylamine hydrochloride) (PAH) and hyaluronic acid (HA) were fabricated in order to study their wet adhesive behavior. The film characteristics were investigated to understand the inherent structures during the assembly process. Subsequently, the adhesion of these systems was evaluated to understand the correlation between the structure of the film and the energy required to separate these LbL assemblies. We describe how the conditions of the LbL fabrication can be utilized to control the adhesion between films. The characteristics of the film formation are examined in the absence and presence of salt during the film formation. The dependence on contact time and LbL film thickness on the critical pull-off force and work of adhesion are discussed. Specifically, by introducing sodium chloride (NaCl) in the assembly process, the pull-off forces can be increased by a factor of 10 and the work of adhesion by 2 orders of magnitude. Adjusting both the contact time and the film thickness enables control of the adhesive properties within these limits. Based on these results, we discuss how the fabrication procedure can create tailored adhesive interfaces with properties surpassing analogous systems found in nature.

    View details for DOI 10.1021/bm501202s

    View details for Web of Science ID 000346114400005

    View details for PubMedID 25333327

  • New insights into the mechanisms behind the strengthening of lignocellulosic fibrous networks with polyamines CELLULOSE Marais, A., Magnusson, M. S., Joffre, T., Wernersson, E. L., Wagberg, L. 2014; 21 (6): 3941-3950
  • Towards a super-strainable paper using the Layer-by-Layer technique CARBOHYDRATE POLYMERS Marais, A., Utsel, S., Gustafsson, E., Wagberg, L. 2014; 100: 218-224

    Abstract

    The Layer-by-Layer technique was used to build a polyelectrolyte multilayer on the surface of pulp fibres. The treated fibres were then used to prepare paper sheets and the mechanical properties of these sheets were evaluated as a function of the number of bi-layers on the fibres. Two different systems were studied: polyethyleneimine (PEI)/nanofibrillated cellulose (NFC), and polyallylamine hydrochloride (PAH)/hyaluronic acid (HA). Model experiments using dual polarization interferometry and SiO₂ surfaces showed that the two systems gave different thicknesses for a given number of layers. The outer layer was found to be a key parameter in the PEI/NFC system, whereas it was less important in the PAH/HA system. The mechanical properties of the sheets made from the PAH/HA treated fibres were significantly greater than those made from untreated fibres, reaching 70 Nm/g in tensile index and 6.5% in strain at break. Such a modification could be very useful for 3D forming of paper, opening new perspectives in for example the packaging industry, with a renewable and biodegradable product as a potential substitute for some of the traditional oil-based plastics.

    View details for DOI 10.1016/j.carbpol.2013.03.049

    View details for Web of Science ID 000330092000028

    View details for PubMedID 24188857

  • Nanocellulose Aerogels Functionalized by Rapid Layer-by-Layer Assembly for High Charge Storage and Beyond ANGEWANDTE CHEMIE-INTERNATIONAL EDITION Hamedi, M., Karabulut, E., Marais, A., Herland, A., Nystrom, G., Wagberg, L. 2013; 52 (46): 12038-12042

    View details for DOI 10.1002/anie.201305137

    View details for Web of Science ID 000326670800019

    View details for PubMedID 24573788

  • Toward an alternative compatibilizer for PLA/cellulose composites: Grafting of xyloglucan with PLA CARBOHYDRATE POLYMERS Marais, A., Kochumalayil, J. J., Nilsson, C., Fogelstrom, L., Gamstedt, E. K. 2012; 89 (4): 1038-1043

    Abstract

    Poly(L-lactic acid) (PLLA) chains were grafted on xyloglucan substrates via ring-opening polymerization of the L-lactide monomer. Different parameters such as the nature of the substrate (native or modified xyloglucan) and the substrate/monomer ratios were varied in the synthesis to achieve different lengths of the grafted chains. A range of experimental techniques including infrared spectroscopy and nuclear magnetic resonance were used to characterize the final product. Thermal analysis showed that the glass transition temperature of xyloglucan was decreased from 252 °C to 216 °C following the grafting of PLLA. The grafting of less hydrophilic chains from xyloglucan also affected the interaction with water: the PLLA-grafted xyloglucan was insoluble in water and the moisture uptake could be decreased by about 30%. Xyloglucan adsorbs strongly to cellulose; therefore such a graft copolymer may improve the compatibility between cellulose fibers and PLLA. The PLLA-grafted xyloglucan may be useful as a novel compatibilizer in fiber-reinforced PLLA composites.

    View details for DOI 10.1016/j.carbpol.2012.03.051

    View details for Web of Science ID 000305593900007

    View details for PubMedID 24750911

  • The use of polymeric amines to enhance the mechanical properties of lignocellulosic fibrous networks CELLULOSE Marais, A., Wagberg, L. 2012; 19 (4): 1437-1447