As
one of the most promising drug delivery carriers, hydrogels have received
considerable attention in recent years. Many previous efforts have
focused on diffusion-controlled release, which allows hydrogels to
load and release drugs in vitro and/or in vivo. However, it hardly
applies to lipophilic drug delivery due to their poor compatibility
with hydrogels. Herein, we propose a novel method for lipophilic drug
release based on a dual pH-responsive hydrogel actuator. Specifically,
the drug is encapsulated and can be released by a dual pH-controlled
capsule switch. Inspired by the deformation mechanism of Drosera leaves,
we fabricate the capsule switch with a double-layer structure that
is made of two kinds of pH-responsive hydrogels. Two layers are covalently
bonded together through silane coupling agents. They can bend collaboratively
in a basic or acidic environment to achieve the “turn on”
motion of the capsule switch. By incorporating an array of parallel
elastomer stripes on one side of the hydrogel bilayer, various motions
(e.g., bending, twisting, and rolling) of the hydrogel bilayer actuator
were achieved. We conducted an in vitro lipophilic drug release test.
The feasibility of this new drug release method is verified. We believe
this dual pH-responsive actuator-controlled drug release method may
shed light on the possibilities of various drug delivery systems.
Mechanical flexibility and electrical reliability establish the fundamental criteria for wearable and implantable electronic devices. In order to receive intrinsically stretchable resistive switching memories, both the electrode and storage media should be flexible yet retain stable electrical properties. Experimental results and finite element analysis reveal that the formation of 3D liquid metal galinstan (GaInSn) calabash bunch conductive network in poly(dimethyl siloxane) (PDMS) matrix allows GaInSn@PDMS composite as soft electrode with the stable conductivity of >1.3 × 103 S cm−1 at the stretching strains of >80% and a fracture strain extreme of 108.14%, while the third‐generation metal–organic framework MIL‐53 thin film with a facial rhombohedral topology enables large mechanical deformation up to a theoretical level of 17.7%. Combining the use of liquid metal–based electrode and MIL‐53 switching layer, for the first time, intrinsically stretchable RRAM device Ag/MIL‐53/GaInSn@PDMS is demonstrated that can exhibit reliable resistive switching characteristics at the strain level of 10%. The formation of fluidic gallium conductive filaments, together with the structural flexibility of the GaInSn@PDMS soft electrode and MIL‐53 insulating layer, accounts for the uniform resistive switching under stretching deformation scenario.
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