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Open Access Publications from the University of California

Scholarly Works (3 results)

  • Thesis
  • Peer Reviewed
UCLA Electronic Theses and Dissertations (2022)

Synthetic hydrophilic polymers are a type of polymers with polar or charged functional groups, and such functional groups render them with favorable interactions with water, leading to solubility or swellability. These polymers have been used in a wide variety of applications because they can be fabricated into novel materials with customized properties through carefully designed synthetic strategy and proper modification.

In the first chapter, a series of polyacrylamide (PAM) based polymers were applied to cohesionless, sandy soil for dust suppression. PAM is a hydrogel, a hydrophilic crosslinked polymer that does not dissolve in water and is a super water absorbent. We copolymerized PAM with hydrophobic units to control the polymer swelling ratio, and thus managed to mitigate the undesirable polymer swelling, soil matrix expansion, and the mechanical strength loss upon wet-dry processes. We further demonstrated that the treatment depth is controllable, which is crucial to minimize environmental impact, by fine-tuning the precursor composition for in-situ curing.

In the second and third chapters, we combined the functions of piezoresistive strain sensing and photothermal actuation into a single material, resembling living organisms’ neuromuscular behaviors. This design solved the limitation of conventional physically-integrated sensory actuator systems with interface constraints and predefined functions. The material composed of an interpenetrating double-network of a nanostructured thermo-responsive hydrogel poly(N-isopropylacrylamide) and a light-absorbing, electrically conductive polymer. When connected to a control circuit, these muscle-like materials achieved closed-loop feedback controlled, reversible step motion.

In the fourth chapter, polydopamine (PDA) nanoparticles mixed with large pore MSNs were used to deliver drugs. This research seeks to develop nanotherapeutics to deliver an ultra-short course tuberculosis treatment regimen via inhalation, for both drug-sensitive and drug-resistant tuberculosis (TB). We shall develop in an iterative process nanotherapeutics that safely and effectively deliver each of the four drugs alone and in combination as well as nanotherapeutics that can deliver multiple drugs. We evaluated the optimized nanotherapeutics for safety and efficacy in treating tuberculosis in a murine model of pulmonary TB when administered via inhalation, both alone and in combination with oral therapy with the same drugs.

    • Article
    • Peer Reviewed
    UCLA Previously Published Works (2020)
    Structural colors of 2D gratings are iridescent, color-tunable, and never fade, which renders them appealing for anti-counterfeiting applications. However, for advanced security, it still remains a challenge to completely hide the encrypted color patterns and reveal them on demand. In this work, a water-responsive photonic grating consisting of a micropillar array and a hydrogel overcoat with a similar refractive index, termed “hydrocipher”, is presented. The joint effect of stimuli-reversible refractive-index (mis)match and reconfigurable grating-based diffraction coloration enables a complete encryption of the structural color and rapid decryption. The photonic structure shows a strong iridescence due to the angle-dependent diffraction when the hydrogel overcoat is swollen from water. Upon drying, the micropillars bend and the refractive index contrast disappears, which dramatically lessens the diffraction intensity and renders the surface highly transparent. The dehydrated-to-hydrated state transition can occur within 1 s, enabling fast decryption. The color switching is highly reversible over a prolonged hydration/dehydration cycle, and the dehydrated hydrogel layer protects the delicate micropillar array from external mechanical stress. The creative combination of hydrogel material and the 2D grating structure offers a new and simple strategy for realizing reversible, durable, and fast-response cryptography with potentially broad impact on the anti-counterfeiting technology market.
      Cover page: Hydrocipher: Bioinspired Dynamic Structural Color‐Based Cryptographic Surface
      • Article
      • Peer Reviewed
      UCLA Previously Published Works (2020)
      Dust generation is a world-wide issue due to its serious deleterious effects on the environment, human health and safety, and the economy. Although various dust suppression methods have been used for decades, some critical drawbacks in state-of-the-art technology still remain unsolved, such as short-lasting, ground water impact, and prone to water. This work reports a soil stabilizer based on non-toxic material and forms a ductile and durable double-network in soil, namely “D3 soil stabilizer”, which not only improves soil mechanical toughness of surface soil but also suppresses dust generation. A copolymer comprising hydrophilic and hydrophobic components combined with enzyme-induced carbonate precipitation is utilized as an in-situ gelation binder to soil particle. The tunable hydrophobic-to-hydrophilic component ratio minimizes undesirable soil matrix expansion and mechanical strength loss upon experiencing wet-dry processes, while still retains good water affinity. We further demonstrated controllable treatment depth by fine-tuning precursor composition, which is essential to minimize environmental impact. The double-network morphology with carbonate precipitate embedded uniformly in polymer matrix is observed via microscopic imaging. The nature of outstanding ductility, high durability against water, and good long-term stability were supported by systematic unconfined compressive strength (UCS) measurements on treated soil, which show strong inter-particles binding, good retention of peak strength, increased strain at peak strength, and increased toughness after soil samples have experienced wet-dry processes.
        Cover page: Durable and ductile double-network material for dust control
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