Nanocomposites of metal nanoparticles (NPs) and bacterial nanocellulose (BC) enable fabrication of soft and biocompatible materials for optical, catalytic, electronic, and biomedical applications. Current BC-NP nanocomposites are typically prepared by in situ synthesis of the NPs or electrostatic adsorption of surface functionalized NPs, which limits possibilities to control and tune NP size, shape, concentration, and surface chemistry and influences the properties and performance of the materials. Here a self-assembly strategy is described for fabrication of complex and well-defined BC-NP composites using colloidal gold and silver NPs of different sizes, shapes, and concentrations. The self-assembly process results in nanocomposites with distinct biophysical and optical properties. In addition to antibacterial materials and materials with excellent senor performance, materials with unique mechanoplasmonic properties are developed. The homogenous incorporation of plasmonic gold NPs in the BC enables extensive modulation of the optical properties by mechanical stimuli. Compression gives rise to near-field coupling between adsorbed NPs, resulting in tunable spectral variations and enhanced broadband absorption that amplify both nonlinear optical and thermoplasmonic effects and enables novel biosensing strategies.

Real-time monitoring of product titers during process development and production of biotherapeutics facilitate implementation of quality-by-design principles and enable rapid bioprocess decision and optimization of the production process. Conventional analytical methods are generally performed offline/at-line and, therefore, are not capable of generating real-time data. In this study, a novel fiber optical nanoplasmonic sensor technology was explored for rapid IgG titer measurements. The sensor combines localized surface plasmon resonance transduction and robust single use Protein A-modified sensor chips, housed in a flexible flow cell, for specific IgG detection. The sensor requires small sample volumes (1–150 µL) and shows a reproducibility and sensitivity comparable to Protein A/G high performance liquid chromatography-ultraviolet (G-HPLC-UV). The dynamic range of the sensor system can be tuned by varying the sample volume, which enables quantification of IgG samples ranging from 0.0015 to 10 mg/mL, without need for sample dilution. The sensor shows limited interference from the sample matrix and negligible unspecific protein binding. IgG titers can be rapidly determined in samples from filtered unpurified Chinese hamster ovary (CHO) cell cultures and show good correlation with enzyme-linked immunosorbent assay (ELISA).

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The emerging stretchable photonics field faces challenges, like the robust integration of optical elements into elastic matrices or the generation of large optomechanical effects. Here, the first stretchable plasmonic‐enhanced and wrinkled Fabry–Pérot (FP) cavities are demonstrated, which are composed of self‐embedded arrays of Au nanostructures at controlled depths into elastomer films. The novel self‐embedding process is triggered by the Au nanostructures’ catalytic activity, which locally increases the polymer curing rate, thereby inducing a mechanical stress that simultaneously pulls the Au nanostructures into the polymer and forms a wrinkled skin layer. This geometry yields unprecedented optomechanical effects produced by the coupling of the broad plasmonic modes of the Au nanostructures and the FP modes, which are modulated by the wrinkled optical cavity. As a result, film stretching induces drastic changes in both the spectral position and intensity of the plasmonic‐enhanced FP resonances due to the simultaneous cavity thickness reduction and cavity wrinkle flattening, thus increasing the cavity finesse. These optomechanical effects are exploited to demonstrate new strain‐sensing approaches, achieving a strain detection limit of 0.006%, i.e., 16‐fold lower than current optical strain‐detection schemes.

Scanning electron microscopy micrographs of BC-AuNP cross section (front, bottom right corner) and of BC (front, top left corner). Back cover shows a light microscopy image of BC-AuNP. During the course of the research underlying this thesis, Olof Eskilson was enrolled in Forum Scientium, a multidisciplinary doctoral program