Despite the versatility of synthetic chemistry, certain combinations of mechanical softness, strength, and toughness can be difficult to achieve in a single material. These combinations are, however, commonplace in biological tissues, and are therefore needed for applications such as medical implants, tissue engineering, soft robotics, and wearable electronics. Present materials synthesis strategies are predominantly Edisonian, involving the empirical mixing of assorted monomers, crosslinking schemes, and occluded swelling agents, but this approach yields limited property control. Here we present a general strategy for mimicking the mechanical behaviour of biological materials by precisely encoding their stress-strain curves in solvent-free brush- and comb-like polymer networks (elastomers). The code consists of three independent architectural parameters-network strand length, side-chain length and grafting density. Using prototypical poly(dimethylsiloxane) elastomers, we illustrate how this parametric triplet enables the replication of the strain-stiffening characteristics of jellyfish, lung, and arterial tissues.

Fundamental understanding of rigid particle indentation into soft elastic substrates has been elusive for decades. In conventional heterogeneous and multicomponent systems, the ill-defined interplay between elastic and capillary forces has confounded explanation of the crossover region between the classical wetting and adhesion regimes. Herein, we study the indentation behavior of micrometer-sized silica particles on supersoft, solvent-free PDMS elastomers with brush-like network strands. By varying the side chain grafting density and the crosslinking density of the networks, we control their elastic modulus from ∼1 to 100 kPa without adding solvent. This isostructurally regulated balance between elastic and capillary forces allows for accurate mapping of the entire range of particle− substrate interactions by measuring indentation depth as a function of substrate stiffness and particle radius. A generalized theoretical model, accounting for the collaborative contribution of both forces to the system free energy, demonstrates excellent quantitative agreement with our experimental results as well as with results of computer simulation for particles in contact with soft surfaces.

The purpose of this study was to describe the development of a valid and reliable rubric to assess secondary-level solo instrumental music performance based on principles of invariant measurement. The research questions that guided this study included (1) What is the psychometric quality (i.e., validity, reliability, and precision) of a scale developed to assess secondary-level solo music performance? (2) Do the proposed items fit the measurement model, and if so, how do the items vary in difficulty? and (3) How does the structure of the rating scale vary across individual items? The psychometric considerations in this study included calibrations of items, persons, raters, school level, musical instrument, and rating scale structure using the Multifaceted Rasch Partial Credit Measurement Model. A 13-member cohort of music content experts participated as raters in this study. A total of 75 video performances of secondary-level solo and ensemble performances were evaluated. The result was the development of the Music Performance Rubric for Secondary-Level Instrumental Solos (MPR-2L-INSTSOLO), a 30-item rubric consisting of rating scale categories ranging from two to four performance criteria. Implications for consequential validity, rater training, standard setting, and benchmarking are discussed.

By controlling polymer-network architecture, we create tissue-like materials to extend soft robot performance to harsh environments.

We present a single-step, grafting-to synthetic method for the encapsulation of particulate NaBH4 by dopamine end-functionalized polymer chains. Metal–catechol coordination chemistry is used to produce core–shell capsules, which generate H2 gas exclusively upon adsorption to an oil–water interface. Significantly, the synthetic process enables facile control of core diameter, shell thickness, and the chemistry of both shell and core. The interfacial reactivity of these stimuli-responsive capsules may be engineered for various applications such as medical diagnostics, therapeutics, and subsurface imaging. In addition to their triggered reactivity, the capsules react in a manner independent of pressure and are thus well-suited for high pressure subsurface environments.