Remotely actuated programmable self-folding origami strings using magnetic induction heating

Transforming planar structures into volumetric objects typically requires manual folding processes, akin to origami. However, manual intervention at sub-centimeter scales is impractical. Instead, folding is achieved using volume-changing smart materials that respond to physical or chemical stimuli, be it with direct contact such as hydration, pH, or remotely e.g., light or magnetism. The complexity of small-scale structures often restricts the variety of smart materials used and the number of folding sequences. In this study, we propose a method to sequentially self-fold millimeter scale origami using magnetic induction heating at 150 kHz and 3.2 mT. Additionally, we introduce a method for designing self-folding overhand knots and predicting the folding sequence using the magneto-thermal model we developed. This methodology is demonstrated to sequentially self-fold by optimizing the surface, placement, and geometry of metal workpieces, and is validated through the self-folding of various structures, including a 380m m 2 croissant, a 321 mm2 box, a 447 mm2 bio-mimetic Mimosa pudica leaf, and an overhand knot covering 524 mm2. Our work shows significant potential for miniature self-folding origami robots owing to the novel sequential folding approach and the ability to achieve remote and tetherless self-folding within constrained environments.

Metal-Organic Framework as a New Type of Magnetothermally-Triggered On-Demand Release Carrier

The development of external stimuli-controlled payload systems has been sought after with increasing interest toward magnetothermally-triggered drug release (MTDR) carriers due to their non-invasive features. However, current MTDR carriers present several limitations, such as poor heating efficiency caused by the aggregation of iron oxide nanoparticles (IONPs) or the presence of antiferromagnetic phases which affect their efficiency. Herein, a novel MTDR carrier is developed using a controlled encapsulation method that fully fixes and confines IONPs of various sizes within the metal-organic frameworks (MOFs). This novel carrier preserves the MOF's morphology, porosity, and IONP segregation, while enhances heating efficiency through the oxidation of antiferromagnetic phases in IONPs during encapsulation. It also features a magnetothermally-responsive nanobrush that is stimulated by an alternating magnetic field to enable on-demand drug release. The novel carrier shows improved heating, which has potential applications as contrast agents and for combined chemo and magnetic hyperthermia therapy. It holds a great promise for magneto-thermally modulated drug dosing at tumor sites, making it an exciting avenue for cancer treatment.

Dual-Responsive Hydrogels with Three-Stage Optical Modulation for Smart Windows

Since room temperature management consumes a large amount of building energy, thermochromic smart windows have been extensively used for temperature regulation and energy management. However, the development of the smart window is still limited by its simple thermochromic performance, unreasonable thermochromic temperature, and the lack of additional stimulation conditions. In this work, a dual-responsive hydrogel was developed by introducing sodium dodecyl sulfate (SDS) and sodium chloride into the cross-linking network of poly(N-isopropylacrylamide) (PNIPAM) and polyacrylamide (PAM) for energy-saving and privacy protection. By controlling the temperature from low (<15 °C) to medium (15-28 °C) to high (>28 °C), the dual-responsive hydrogel achieved a reversible three-stage transition of opaque-transparent-translucent. The hydrogel exhibited a satisfactory solar modulation ability (T_lum = 80.3%, ΔT_sol,15-18°C = 72.9%, ΔT_sol,18-35°C = 42.7%) and effective IR and UV shielding at high (or low) temperatures. Moreover, compared with traditional windows, smart windows made of dual-responsive hydrogels could offer better thermal insulation and heat preservation. The electrochromic properties of the dual-responsive hydrogel presented a facile strategy to meet the needs of different situations. The dual-responsive hydrogel features energy-saving, privacy protection, three-stage optical modulation, and multistimulus responsiveness, making it an ideal smart window candidate.

Weakly Ionically Bound Thermosensitive Hyperbranched Polymers

We synthesized novel amphiphilic hyperbranched polymers (HBPs) with variable contents of weakly ionically tethered thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) macrocations in contrast to traditional covalent linking. Their assembling behavior was studied below and above the lower critical solution temperature (LCST). The HBPs underwent a morphological transition under changing temperature and ionic strength due to the LCST transition of PNIPAM and the reduction in the ionization degree of terminal ionic groups, respectively. We suggest that, in contrast to traditional branched polymers, ionically linked PNIPAM macrocations can reversibly disassociate from the sulfonate groups and form mobile coronas, endowing the dynamic micellar morphologies. In addition, assembly at the air-water interface confined PNIPAM macrocations and resulted in the formation of heterogeneous Langmuir-Blodgett (LB) monolayers with diverse surface morphologies for different peripheral compositions with circular domains formed in the condensed state. The HBPs with 25% PNIPAM showed larger and more stable circular domains that were partially preserved at high compression than those of HBPs with 50% PNIPAM. Moreover, the LB monolayers showed variable surface mechanical and surface charge distribution, which can be attributed to net dipole redistribution caused by the behavior of mobile PNIPAM macrocations and core sulfonate groups.

Point-of-Care Diagnostics: Molecularly Imprinted Polymers and Nanomaterials for Enhanced Biosensor Selectivity and Transduction

Significant healthcare disparities resulting from personal wealth, circumstances of birth, education level, and more are internationally prevalent. As such, advances in biomedical science overwhelmingly benefit a minority of the global population. Point-of-Care Testing (POCT) can contribute to societal equilibrium by making medical diagnostics affordable, convenient, and fast. Unfortunately, conventional POCT appears stagnant in terms of achieving significant advances. This is attributed to the high cost and instability associated with conventional biorecognition: primarily antibodies, but nucleic acids, cells, enzymes, and aptamers have also been used. Instead, state-of-the-art biosensor researchers are increasingly leveraging molecularly imprinted polymers (MIPs) for their high selectivity, excellent stability, and amenability to a variety of physical and chemical manipulations. Besides the elimination of conventional bioreceptors, the incorporation of nanomaterials has further improved the sensitivity of biosensors. Herein, modern nanobiosensors employing MIPs for selectivity and nanomaterials for improved transduction are systematically reviewed. First, a brief synopsis of fabrication and wide-spread challenges with selectivity demonstration are presented. Afterward, the discussion turns to an analysis of relevant case studies published in the last five years. The analysis is given through two lenses: MIP-based biosensors employing specific nanomaterials and those adopting particular transduction strategies. Finally, conclusions are presented along with a look to the future through recommendations for advancing the field. It is hoped that this work will accelerate successful efforts in the field, orient new researchers, and contribute to equitable health care for all.

Thermomagneto-Responsive Smart Biocatalysts for Malonyl-Coenzyme A Synthesis

Smart biocatalysts, in which enzymes are conjugated to stimuli-responsive polymers, have gained considerable attention because of their catalytic switchability and recyclability. Although many systems have been developed, they require separate laboratory techniques for their recovery, making them unsuitable for many practical applications. To address these issues, we designed a thermomagneto-responsive biocatalyst by immobilizing an enzyme on the terminal of thermo-responsive polymer brushes tethered on magnetic nanoparticle (NP) clusters. The concept is demonstrated by a system consisting of iron oxide NPs, poly(N-isopropyl-acrylamide), and a malonyl-Coenzyme A synthetase (MatB). By using free malonate and coenzyme A (CoA), the designed catalyst exhibits adequate activity for the production of malonyl-CoA. Thanks to the use of a magnetic NP cluster, whose magnetic moment is high, this system is fully recoverable under the magnetic field at above 32 °C because of the collapse of the thermo-responsive polymer shell in the clusters. In addition, the recycled catalyst maintains moderate activity even after three cycles, and it also shows excellent catalytic switchability, that is, negligible catalytic activity at 25 °C because of the blockage of the active sites of the enzyme by the extended hydrophilic polymer chains but great catalytic activity at a temperatures above the lower critical solution temperature at which the enzymes are exposed to the reaction medium because of the thermo-responsive contraction of polymer chains. Because the azide functionality in our system can be easily functionalized depending upon our need, such catalytically switchable, fully recoverable, and recyclable multiresponsive catalytic systems can be of high relevance for other cell-free biosynthetic approaches.

Transformations of Thermosensitive Hyperbranched Poly(ionic liquid)s Monolayers

We synthesized amphiphilic hyperbranched poly(ionic liquid)s (HBPILs) with asymmetrical peripheral composition consisting of hydrophobic n-octadecylurethane arms and hydrophilic, ionically linked poly(N-isopropylacrylamide) (PNIPAM) macrocations and studied low critical solution temperature (LCST)-induced reorganizations at the air-water interface. We observed that the morphology of HBPIL Langmuir monolayers is controlled by the surface pressure with uniform well-defined disk-like domains formed in a liquid phase. These domains are merged and transformed to uniform monolayers with elevated ridge-like network structures representing coalesced interdomain boundaries in a solid phase because the branched architecture and asymmetrical chemical composition stabilize the disk-like morphology under high compression. Above LCST, elevated individual islands are formed because of the aggregation of the collapsed hydrophobized PNIPAM terminal macrocations in a solid phase. The presence of thermoresponsive PNIPAM macrocations initiates monolayer reorganization at LCST with transformation of surface mechanical contrast distribution. The heterogeneity of elastic response and adhesion distributions for HBPIL monolayers in the wet state changed from highly contrasted two-phase distribution below LCST to near-uniform mechanical response above LCST because of the hydrophilic to hydrophobic transformation of the PNIPAM phase.

Nanobiotechnology medical applications: Overcoming challenges through innovation

Biomedical Nanotechnology (BNT) has rapidly become a revolutionary force that is driving innovation in the medical field. BNT is a subclass of nanotechnology (NT), and often operates in cohort with other subclasses, such as mechanical or electrical NT for the development of diagnostic assays, therapeutic implants, nano-scale imaging systems, and medical machinery. BNT is generating solutions to many conventional challenges through the development of enhanced therapeutic delivery systems, diagnostic techniques, and theranostic therapies. Therapeutically, BNT has generated many novel nanocarriers (NCs) that each express specifically designed physiochemical properties that optimize their desired pharmacokinetic profile. NCs are also being integrated into nanoscale platforms that further enhance their delivery by controlling and prolonging their release profile. Nano-platforms are also proving to be highly efficient in tissue regeneration when combined with the appropriate growth factors. Regarding diagnostics, NCs are being designed to perform targeted delivery of luminescent tags and contrast agents that enhance the NC -aided imaging capabilities and resulting diagnostic accuracy of the presence of diseased cells. This technology has also been advancing the ability for surgeons to practice true precision surgical techniques. Incorporating therapeutic and diagnostic NC-components within a single NC can facilitate both functions, referred to as theranostics, which facilitates real-time in vivo tracking and observation of drug release events via enhanced imaging. Additionally, stimuli-responsive theranostic NCs are quickly developing as vectors for tumor ablation therapies by providing a model that facilitates the location of cancer cells for the application of an external stimulus. Overall, BNT is an interdisciplinary approach towards health care, and has the potential to significantly improve the quality of life for humanity by significantly decreasing the treatment burden for patients, and by providing non-invasive therapeutics that confer enhanced therapeutic efficiency and safety

Photopolymerization-based synthesis of iron oxide nanoparticle embedded PNIPAM nanogels for biomedical applications

Conventional therapeutic techniques treat patients by delivering biotherapeutics to the entire body. With targeted delivery, biotherapeutics are transported to the afflicted tissue reducing exposure to healthy tissue. Targeted delivery devices are minimally composed of a stimuli responsive polymer allowing triggered release and magnetic nanoparticles enabling targeting as well as alternating magnetic field (AMF) heating. Although more traditional methods, like emulsion polymerization, have been used to realize such devices, the synthesis is problematic. For example, surfactants preventing agglomeration must be removed from the product increasing time and cost. Ultraviolet (UV) photopolymerization is more efficient and ensures safety by using biocompatible substances. Reactants selected for nanogel fabrication were N-isopropylacrylamide (monomer), methylene bis-acrylamide (crosslinker), and Irgacure 2959 (photoinitiator). The 10 nm superparamagnetic nanoparticles for encapsulation were composed of iron oxide. Herein, a low-cost, scalable, and rapid, custom-built UV photoreactor with in situ, spectroscopic monitoring system is used to observe synthesis. This method also allows in situ encapsulation of the magnetic nanoparticles simplifying the process. Nanogel characterization, performed by transmission electron microscopy, reveals size-tunable nanogel spheres between 40 and 800 nm in diameter. Samples of nanogels encapsulating magnetic nanoparticles were subjected to an AMF and temperature increase was observed indicating triggered release is possible. Results presented here will have a wide range of applications in medical sciences like oncology, gene delivery, cardiology, and endocrinology.