Research of biocompatible polymers is critical for advancing biomedical technologies, particularly in the fields of tissue engineering, drug delivery, and cardiovascular health. This study investigates the mechanical properties of a series of novel biocompatible polymers using Brillouin microspectroscopy. We demonstrate the ability of Brillouin spectroscopy to accurately measure mechanical properties of these polymers on a microscopic level, which are vital for their application and can be finely tuned to match the requirements. Our findings suggest that Brillouin microspectroscopy, coupled with Raman spectroscopy, offers a powerful complementary approach to traditional viscoelasticity measurement techniques, paving the way for enhanced characterization and utilization of biocompatible polymers in medical research and clinical practice. This in turn would help streamline production and control of these polymers in a non-invasive and label-free way.

Probiotics offer therapeutic benefits by modulating the local microbiome, the host immune response, and the proliferation of pathogens. Probiotics have the potential to treat complex diseases, but their persistence or colonization is required at the target site for effective treatment. Although probiotic persistence can be achieved by repeated delivery, no biomaterial that releases clinically relevant doses of metabolically active probiotics in a sustained manner has been previously described. Here, we encapsulate stiff probiotic microorganisms within relatively less stiff hydrogels and show a generic mechanism where these microorganisms proliferate and induce hydrogel fracture, resulting in microbial release. Importantly, this fracture-based mechanism leads to microorganism release with zero-order release kinetics. Using this mechanism, small (∼1 μL) engineered living materials (ELMs) release >108 colony-forming-units (CFUs) of Escherichia coli in 2 h. This release is sustained for at least 100 days. Cell release can be varied by more than 3 orders of magnitude by varying initial cell loading and modulating the mechanical properties of the encapsulating matrix. As the governing mechanism of microbial release is entirely mechanical, we demonstrate the controlled release of model Gram-negative, Gram-positive, and fungal probiotics from multiple hydrogel matrices.

The development of fibrous actuators with diverse actuation modes is expected to accelerate progress in active textiles, robotics, wearable electronics, and haptics. Despite the advances in responsive polymer-based actuating fibers, the available actuation modes are limited by the exclusive reliance of current technologies on thermotropic contraction along the fiber axis. To address this gap, the present study describes a reversible and spontaneous thermotropic elongation (~30%) in liquid crystal elastomer fibers produced via ultraviolet-assisted melt spinning. This elongation arises from the orthogonal alignment of smectogenic mesogens relative to the fiber axis, which contrasts the parallel alignment typically observed in nematic liquid crystal elastomer fibers and is achieved through mesophase control during extrusion. The fibers exhibiting thermotropic elongation enable active textiles increase pore size in response to temperature increase. The integration of contracting and elongating fibers within a single textile enables spatially distinct actuation, paving the way for innovations in smart clothing and fiber/textile actuators.

Stress urinary incontinence (SUI) is the involuntary leakage of urine in response to increased intra-abdominal pressure during episodes of exertion. A common treatment method for SUI is sling implantation underneath the urethra to provide support. Most current sling procedures, however, cannot adjust urethral tension postoperatively. To address this limitation, we designed a soft magnetoactive elastomer (MAE) device capable of changing shape in response to moderate magnetic fields. To ensure shape change after fibrotic scar tissue encapsulation, MAE devices were embedded in agar gels with different stiffnesses, and their shape change was studied in response to up to 200 mT magnetic fields. A simple in vitro model of the lower urinary tract was designed to study device performance. Flow time was measured as a function of pressure in the simulated bladder as the model system leaked before and after activating sling with a hand-held magnet. MAE devices embedded in agar gel (100 kPa) in hammock-like configuration achieved 4.7% f 1.1% change in height. Devices with silicacoated magnetic particles showed minimal loss in mass after two weeks in accelerated oxidative (2.36% f 1.55%) and hydrolytic (0.58% f 0.25%) conditions. Placing a sling under the model urethra provided urethral support; thus, increasing its resistance to flow. Normalized flow time significantly reduced from 1.56 f 0.18 to 1.11 f 0.16 when magnetic field was applied, indicating urethral support modulation at 60 cm-H2O. This dynamic sling, powered externally with physiologically safe magnetic fields, allowed for urethral support modulation in a model of the lower urinary tract. Statement of significance: Stress urinary incontinence (SUI) affects up to half the adult women during their lifetime, and slings are commonly used to treat severe cases. While sling implantation is minimally invasive and offers moderate to high cure rates, long-term sling complications, such as urine retention, remain a significant concern. Available adjustable SUI devices often require invasive surgeries, implantable electronics, and multiple mechanical components, increasing the overall invasiveness. Here, we report a proof of concept for using shapemorphing biomaterials to fabricate a dynamic device that can provide continence support and be triggered to change shape, enabling complete voiding. Such a dynamic device may prevent many complications associated with traditional slings and improve quality of life for women suffering from severe SUI.

Curved electronics hold immense promise for applications ranging from flexible displays to biomedical devices. Transitioning from conventional planar fabrication to three-dimensional (3D) geometries remains a significant challenge. To manufacture 3D electronics, either the patterning process must be adapted to 3D forms, or planar substrates must be deformed into 3D shapes. Liquid crystal elastomers (LCEs) offer a promising platform by enabling intrinsic shape change from flat to intricate 3D forms through controlled molecular alignment. By patterning LCE surfaces with conductive traces prior to deformation, curved electronics can be fabricated using established planar deposition methods. Cross-linking LCEs with programmed molecular alignment at elevated temperatures allows for the fabrication of films that can adopt tunable normal and Gaussian curvature near room temperature. Increasing the nematic-isotropic transition temperature (T NI) of the LCE allows for a wide range of cross-linking temperatures, which in turn allows for the magnitude of the deformation to be controlled. Here, we present a tunable LCE composition with a T NI up to 162 +/- 2 degrees C. Moreover, we fabricate hemispherical films with radii of curvature ranging from 24.57 +/- 2.46 to 41.31 +/- 2.82 mm at room temperature. Additionally, the effect of metallization on the deformation of LCEs into 3D forms is characterized. We envision applications for this 3D electronic fabrication platform for wearable devices in health monitoring systems designed to integrate with curvilinear human anatomy.

Interactions between active individuals in animal collectives lead to emergent responses that remain elusive in synthetic soft matter. Here, shape-morphing polymers serve to create bio-inspired transient solids that self-assemble with controlled mechanical properties and disassemble on demand. Dilute suspensions of magnetic, heat-responsive liquid crystal elastomer ribbons mechanically interlock, inducing reversible aggregation. A mathematical model is developed that sheds light on the role of topological mechanisms in aggregation. Aggregation was favored for ribbons with moderate curvature as compared to flat ribbons or higher-curvature ribbons. The ribbon suspensions reversibly transition between fluid-and solid-like states, exhibiting an increase of up to six orders of magnitude in the storage moduli of the entangled aggregates compared with the liquid dispersions. Controlled dissociation is induced by imparting kinetic energy to the individual ribbons at high magnetic-field rotation speeds (>3:33 Hz). Imparting dynamic collective behaviors into synthetic systems may enable potential applications from bio-inspired soft robotics to injectable biomaterials.

Soft materials capable of controlled shape changes near ambient temperature are of interest for active devices that interact with living organisms. In this study, we achieve such functionalities by synthesizing responsive elastomers based on polydiethylsiloxane (PDES). Unlike conventional silicones, PDES elastomers are mesomorphic. Without any reinforcing additives, the mesophase improves the toughness of PDES to 8 times that of neat polydimethylsiloxane (PDMS) elastomers and 4 times that of Sylgard 184. Uniaxially stretched mesomorphic PDES elastomers undergo reversible shape changes under a bias load in response to temperature, generating 14% contractile strain on heating from 0 to 40 °C. The utility of PDES elastomers as actuators is enhanced by fabricating them into twisting actuators and describing strategies to minimize hysteresis during shape change cycles. The combination of toughness, actuation near ambient temperature, and environmental stability suggests that PDES could be attractive for biomedical devices where soft actuators interface with living organisms.

As actuated devices become smaller and more complex, there is a need for smart materials and structures that directly function as complete mechanical units without an external power supply. The strategy uses light-powered, twisted, and coiled azobenzene-functionalized semicrystalline liquid crystal elastomer (AC-LCE) springs. This twisting and coiling, which has previously been used for only thermally, electrochemically, or absorption-powered muscles, maximizes uniaxial and radial actuation. The specially designed photochemical muscles can undergo about 60% tensile stroke and provide 15 kJ m-3 of work capacity in response to light, thus providing about three times and two times higher performance, respectively, than previous azobenzene actuators. Since this actuation is photochemical, driven by ultraviolet (UV) light and reversed by visible light, isothermal actuation can occur in a range of environmental conditions, including underwater. In addition, photoisomerization of the AC-LCEs enables unique latch-like actuation, eliminating the need for continuous energy application to maintain the stroke. Also, as the light-powered muscles processed to be either homochiral or heterochiral, the direction of actuation can be reversed. The presented approach highlights the novel capabilities of photochemical actuator materials that can be manipulated in untethered, isothermal, and wet environmental conditions, thus suggesting various potential applications, including underwater soft robotics. Synthesis, processing, and designing approaches of photochemically controllable and mechanically robust smart spring actuators are presented here. By combining azobenzene into a semicrystalline liquid crystal elastomer matrix (AC-LCE), several unprecedented properties can be realized within a single material system, including enhanced actuation stress, twist processability, and large-stroke latch-like underwater actuation. image

Uncontrolled hemorrhage is the predominant cause of preventable combat deaths. Various biomaterials serve as hemostatic agents due to their procoagulant or absorptive activity. However, these biomaterials often lack expansion capabilities, which severely limits use in noncompressible wounds. This study combines a hemostatic nanocomposite with a shape-memory polymer foam to design a composite material with both hemostatic and physical expansion properties. This composite is fabricated in two formulations: a foam externally coated in a highly concentrated nanocomposite ("coated composite") and a foam containing a diluted nanocomposite infused throughout its pores ("infused composite"). Both formulations retain the shape-memory foam's expansion property. Further, the coated composite shows improved fluid uptake (>2-fold) versus infused composites or foam. The nanocomposite component dissociates from the foam under degradative conditions, with the foam remaining stable for 30 days. Hemostatic studies illustrate that the coated composite reduces the clotting time by ≈20%. Alternatively, the infused composite improves clotting over a larger distance (up to ≈2× distance from the composite). These results signify a modular hemostatic ability: the coated composite reduces clotting and improves fluid uptake, while the infused composite achieves diffuse clotting and maintains mechanical properties. Thus, these materials pose a strong potential for use in noncompressible wounds.

The development of highly sensitive multinuclear RF coils for MRI/S is challenging because most current multi-tuning techniques involve the addition of lossy components. Although it is possible to optimize for a particular nucleus, usually non-1H, multinuclear coils have lower SNR than their single-tuned counterparts. We investigate a novel switching system that uses stimuli-responsive materials. The coils with the proposed switching method had a decrease of <26% in Q when compared to single-tuned coils. As a result, we demonstrated a promising alternative to traditional switching techniques.

Urinary tract infection (UTI) is one of the most common bacterial infections worldwide. The main causative agent of UTI is uropathogenic Escherichia coli (UPEC). There is an immediate need for novel prophylactic and treatment strategies against UTI because of the increasing incidence of antimicrobial resistance among uropathogens. ABU 83972, an asymptomatic bacteriuria-causing E. coli strain, prevents UTI by suppressing the colonization of UPEC. However, the nature of competition and growth repression of UPEC by ABU 83972 is unclear and is the subject of our investigation. Here, we characterized the growth kinetics of ABU 83972 and uropathogens in human urine and laboratory media. Next, we performed a series of competitive co-culture experiments where ABU 83972 and uropathogens were inoculated at a 1:1 ratio in human urine and in various media, and their relative abundance was determined. In human urine, ABU 83972 outcompeted UPEC and additional uropathogens, reaching up to 90% of the total population after 24 hours of incubation. In contrast, UPEC outcompeted ABU 83972 in LB and M9 minimal media and exhibited superior colonization than ABU 83972 in the mouse urinary bladder. Since engineered living materials (ELMs) can be used to retain an organism of interest in a particular location, we developed ABU 83972-containing ELMs that effectively outcompeted UPEC in human urine. In summary, our work establishes that ABU 83972 outcompetes UPEC in a milieu- and cell-density-dependent manner, highlighting the importance of the metabolites and nutrients found in the human urine as determinants of the competitive fitness of ABU 83972.

The growth of multicellular organisms is a process akin to additive manufacturing where cellular proliferation and mechanical boundary conditions, among other factors, drive morphogenesis. Engineers have limited ability to engineer morphogenesis to manufacture goods or to reconfigure materials comprised of biomass. Herein, a method that uses biological processes to grow and regrow magnetic engineered living materials (mELMs) into desired geometries is reported. These composites contain Saccharomyces cerevisiae and magnetic particles within a hydrogel matrix. The reconfigurable manufacturing process relies on the growth of living cells, magnetic forces, and elastic recovery of the hydrogel. The mELM then adopts a form in an external magnetic field. Yeast within the material proliferates, resulting in 259 ± 14% volume expansion. Yeast proliferation fixes the magnetic deformation, even when the magnetic field is removed. The shape fixity can be up to 99.3 ± 0.3%. The grown mELM can recover up to 73.9 ± 1.9% of the original form by removing yeast cell walls. The directed growth and recovery process can be repeated at least five times. This work enables ELMs to be processed and reprocessed into user-defined geometries without external material deposition.

CO2-based aliphatic polycarbonates (aPCs), produced through the alternating copolymerization of epoxides with CO2, present an appealing option for sustainable polymeric materials owing to their renewable feedstock and degradable characteristics. An ongoing challenge in working with aPCs is modifying their mechanical properties to meet specific demands. Herein, we report that monomer ratio and polymer architecture of aPCs impact not only printability by digital light processing (DLP) additive manufacturing, but also dictate the thermomechanical and degradation properties of the printed objects. We found that block copolymers exhibit tailorable thermomechanical properties ranging from soft elastomeric to strong and brittle as the proportion of hard blocks increases, whereas the homopolymer blend failed to print objects and statistical copolymers delaminated or overcured, displaying the weakest mechanical properties. In addition, the hydrolytic degradation of the prints was demonstrated under various conditions, revealing that BCP prints containing a higher proportion of hard blocks had slower degradation and that statistical copolymer prints degraded more slowly than their BCP counterparts. This study underscores that polymer composition and architecture both play key roles in resin printability and bulk properties, offering significant prospects for advancing sustainable materials in additive manufacturing through polymer design.

Ionic liquid crystals have received increasing interest due to their positional and/or orientational order as well as the freedom in molecular motions that arise from the formation of mesophases between solid and liquid. While phase changes of non-fluorinated ionic liquids have been widely reported, there have been few reports on the temperature-dependent phase behavior of fluorinated ionic liquids. Here, we present a series of fluorinated ionic liquids with methylimidazolium cations bearing 1H, 1H, 2H, 2H-perfluoroalkyl chains (butyl, hexyl, and octyl) and halide counterions, and demonstrate their thermotropic mesomorphism. These cations were synthesized under solvent-free conditions, and anion exchange was used to vary the halide counterion. The thermal stability of the compounds was studied using thermogravimetric analysis and differential scanning calorimetry revealed both liquid crystalline phases and solid-solid transitions. We discovered that the mesomorphic properties of the ionic liquids depend strongly on the length of the polyfluoroalkyl pendants. Specifically, ionic liquids with a fluorinated butyl chain showed no mesophase behavior while those with hexyl and octyl fluorinated chains displayed liquid crystalline phases at temperatures above 100°C. The mesophases were further characterized by polarized optical microscopy and powder X-ray diffraction, highlighting the impact of the fluorinated alkyl chain length.

Some animals form transient, responsive and solid-like ensembles through dynamic structural interactions. These ensembles demonstrate emergent responses such as spontaneous self-assembly, which are difficult to achieve in synthetic soft matter. Here we use shape-morphing units comprising responsive polymers to create solids that self-assemble, modulate their volume and disassemble on demand. The ensemble is composed of a responsive hydrogel, liquid crystal elastomer or semicrystalline polymer ribbons that reversibly bend or twist. The dispersions of these ribbons mechanically interlock, inducing reversible aggregation. The aggregated liquid crystal elastomer ribbons have a 12-fold increase in the yield stress compared with cooled dispersion and contract by 34% on heating. Ribbon type, concentration and shape dictate the aggregation and govern the global mechanical properties of the solid that forms. Coating liquid crystal elastomer ribbons with a liquid metal begets photoresponsive and electrically conductive aggregates, whereas seeding cells on hydrogel ribbons enables self-assembling three-dimensional scaffolds, providing a versatile platform for the design of dynamic materials.

Stress urinary incontinence (SUI) is characterized by the involuntary loss of urine due to increased intra-abdominal pressure during coughing, sneezing, or exercising. SUI affects 20-40% of the female population and is exacerbated by aging. Severe SUI is commonly treated with surgical implantation of an autologous or a synthetic sling underneath the urethra for support. These slings, however, are static, and their tension cannot be non-invasively adjusted, if needed, after implantation. This study reports the fabrication of a novel device based on liquid crystal elastomers (LCEs) capable of changing shape in response to temperature increase induced by transcutaneous IR light. The shape change of the LCE-based device was characterized in a scar tissue phantom model. An in vitro urinary tract model was designed to study the efficacy of the LCE-based device to support continence and adjust sling tension with IR illumination. Finally, the device was acutely implanted and tested for induced tension changes in female multiparous New Zealand white rabbits. The LCE device achieved 5.6% +/- 1.1% actuation when embedded in an agar gel with an elastic modulus of 100 kPa. The corresponding device temperature was 44.9 degrees C +/- 0.4 degrees C, and the surrounding agar temperature stayed at 42.1 degrees C +/- 0.4 degrees C. Leaking time in the in vitro urinary tract model significantly decreased (p < 0.0001) when an LCE-based cuff was sutured around the model urethra from 5.2min +/- 1min to 2min +/- 0.5min when the cuff was illuminated with IR light. Normalized leak point force (LPF) increased significantly (p = 0.01) with the implantation of an LCE-CB cuff around the bladder neck of multiparous rabbits. It decreased significantly (p = 0.023) when the device was actuated via IR light illumination. These results demonstrate that LCE material could be used to fabricate a dynamic device for treating SUI in women.

Exploiting the interplay of anisotropic diamagnetic susceptibility of liquid crystalline monomers and site selective photopolymerization enables the fabrication of 3D freeforms with highly refined microstructures. Utilizing chain transfer agents in the mesogenic inks presents a pathway for broadly tuning the mechanical properties of liquid crystalline polymers and their response to stimuli. In particular, the combination of 1,4-benzenedimethanethiol and tetrabromomethane is shown to enable voxelated blueprinting of molecular order, while allowing for a modulation of the crosslink density and the mechanical properties. The formulation of these monomers allows for the resolution of the voxels to approach the limits set by the coherence lengths defined by the anchoring from surfaces. These compositions demonstrate the expected thermotropic responses while allowing for their functionalization with photochromic switches to elicit photomechanical responses. Actuation strains are shown to outstrip that accomplished with prior systems that did not access chain transfer agents to modulate the structure of the macromolecular network. Test cases of this system are shown to create freeform actuators that exploit the refined director patterns during high-resolution printing. These include topological defects, hierarchically-structured light responsive grippers, and biomimetic flyers whose flight dynamics can be actively modulated via irradiation with light. Exploiting the interplay of anisotropic diamagnetic susceptibility of liquid crystalline monomers and site selective photopolymerization enables the fabrication of 3D freeforms with highly refined microstructures.