Pectin films mimic the sensing mechanism of viper pit membranes to finely detect temperature changes.

Conventional approaches to create biomaterials rely on reverse engineering of biological structures, on biomimicking, and on bioinspiration. Plant nanobionics is a recent approach to engineer new materials combining plant organelles with synthetic nanoparticles to enhance, for example, photosynthesis. Biological structures often outperform man-made materials. For example, higher plants sense temperature changes with high responsivity. However, these properties do not persist after cell death. Here, we permanently stabilize the temperature response of isolated plant cells adding carbon nanotubes (CNTs). Interconnecting cells, we create materials with an effective temperature coefficient of electrical resistance (TCR) of −1,730% K −1 , ∼2 orders of magnitude higher than the best available sensors. This extreme temperature response is due to metal ions contained in the egg-box structure of the pectin backbone, lodged between cellulose microfibrils. The presence of a network of CNTs stabilizes the response of cells at high temperatures without decreasing the activation energy of the material. CNTs also increase the background conductivity, making these materials suitable elements for thermal and distance sensors.temperature sensor | plant nanobionics | carbon nanotubes | iontronics | biomaterials M aterials that respond sensitively to temperature variations are used in several applications that range from electrical temperature sensors (1) to microbolometers for thermal cameras (2, 3). Existing high-performance temperature-sensitive materials, such as vanadium oxide, have temperature coefficient of electrical resistance (TCR) on the order of −6% K −1 at room temperature (4). These materials derive their properties from changes of their crystal structure during semiconductor to metal transitions (5). Higher sensitivities have been pursued by exploiting quantum effects (6-9), e.g., in carbon nanotube (CNT) composites (1). However, such composites reach lower TCRs because CNTs are embedded in an insulating polymeric matrix (1).Variations of the ambient temperature influence the biopotential of living plants (10,11). Experiments performed in vivo on a maple tree (Acer saccharum) showed an exponential correlation between the tree's branch electrical resistance and temperature (10). This behavior has been attributed to ionic conductivity occurring in plant cell walls (11). The plant cell wall has a highly complex macromolecular architecture with very dynamic structural and physiological properties (12). The cell wall, positioned outside the plasma membrane (13), is composed of carbohydrates such as cellulose microfibrils (14) with diameters as small as 3.0 nm (15) and hemicellulose interconnected with pectin. Pectins are composed of pectic polysaccharides rich in galacturonic acid that influence properties such as porosity, surface charge, pH, and ion balance and therefore are critical for ion transport within the cell wall. Pectins contain multiple negatively charged saccharides that bind cations, such as Ca 2+, that for...

The development of strategies to reduce the load of unwanted bacteria is a fundamental challenge in industrial processing, environmental sciences and medical applications. Here, we report a new method to sequester motile bacteria from a liquid, based on passive, deployable micro-traps that confine bacteria using micro-funnels that open into trapping chambers. Even in low concentrations, micro-traps afford a 70% reduction in the amount of bacteria in a liquid sample, with a potential to reach >90% as shown by modelling improved geometries. This work introduces a new approach to contain the growth of bacteria without chemical means, an advantage of particular importance given the alarming growth of pan-drug-resistant bacteria.