Abstract
Valves are largely useful for treatment assistance devices, e.g., supporting fluid circulation movement in the human body. However, the valves presently used in biomedical applications still use materials that are rigid, non-compliant, and hard to integrate with human tissues. Here, we propose biologically-inspired, stimuli-responsive valves and evaluate N-Isopropylacrylamide hydrogels-based valve (NPHV) and PAAm-alginate hydrogels-based valve (PAHV) performances with different chemical syntheses for optimizing better valve action. Once heated at 40 C, the NPHV outperforms the PAHV in annular actuation (NPHV: 1.93 mm displacement in 4 min; PAHV: 0.8 mm displacement in 30 min). In contrast, the PAHV exhibits a flow rate change of up to 20%, and a payload of 100% when the object is at 100 C. The PAHV demonstrated a completely soft, stretchable circular gripper with a high load-to-weight ratio for diversified applications. These valves are fabricated with a simple one-pot method that, once further optimized, can offer transdisciplinary applications.
Highlights
IntroductionA sudden drop in the ambient temperature leads to blood vessel contraction and yields to shivering [1]
Here we demonstrate a N-Isopropylacrylamide hydrogels-based valve (NPHV) that provides a new outlook based on temperature changes, and compares valve performance with previously established PAAm-Alginate hydrogels [8]
(b) Time-lapse images demonstrating the PAAm-alginate hydrogels-based valve (PAHV) grasping. (c) IR images exhibiting the PAHV gripper’s actuation when the object is at 100 ◦ C. (d) Temperature in the PAHV when the object is at 100 ◦ C. (e) Displacement in the PAHV when the object is at 100 ◦ C. (f) Object slipping in the PAHV gripper during grasping for 3 cycles when object is at 100 ◦ C
Summary
A sudden drop in the ambient temperature leads to blood vessel contraction and yields to shivering [1] These biochemical processes lead to inspiration for engineering materials to mimic the stimuli-responsive mechanism as an efficient energy conversion mechanism (e.g., chemical to mechanical). A detailed rheological analysis can be useful in choosing thermoresponsive hydrogels and their pseudo-plasticity with the viscoelastic transition [15,16] This has a significant impact that in turn offers a lightweight and biocompatible system with fine control [9,17,18,19,20,21]. Application avenues of these mechanically-compliant biomaterials include soft robotics [22], stretchable electronics [23], artificial skin [24], safer human–machine interaction [25], biologically-inspired valves [26], drug release [27], microfluidics [28], and more [29,30,31]
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