Skin-inspired hydrogel–elastomer hybrids with robust interfaces and functional microstructures

Inspired by the mammal skin, a soft blend that combines the advantages of elastic materials and gels has potential applications in different fields such as stretching and biology
Integrated Electronic, micro-fluid, tissue engineering, soft robotics and biomedical equipment.
However, existing gel-elastic composites have limitations such as weak interface binding, low robustness and difficulty in forming micro-structures of patterns.
Here, we report a simple and general approach to assembling gel and elastomer into a hybrid material with a very strong interface (
Interface toughness of more than 1,000
Function structures such as micro-flow control channels and circuits.
The proposed method is generally applicable to various types of tough gel and a variety of commonly used rubber, including polydione Sylgard 184, polyurethane, latex, VHB and Ecoflex.
We further demonstrate a gel-elastic mixture consisting of a solid and micro-structure (including resistance
Dehydrated gel-elastic mixture, pull-up and reactive gel-elastic microfluid and stretch-able gel circuit board with elastic pattern.
Unless otherwise specified, the chemicals currently used at work are from Sigma-
Use without further purification.
For the bonded cross-linked elastic polymer network in tough gels, propylene amide (AAm; Sigma-Aldrich A8887)
Monomer for PAAm network, and peg da for 20kda kd (Sigma-Aldrich 767549)
Is a macro unit for the PEGDA network.
For PAAm gel ,-
Propylene amine (MBAA; Sigma-Aldrich 146072)
Used as a linker and 2-Hydroxy-4′-(2-hydroxyethoxy)-2-
Acetone toluene (Irgacure 2959; Sigma-Aldrich 410896)
Used as a light trigger.
Peg da gel was prepared with Irgacure 2959 as photo initiator.
For the physical cross-linking dissipated polymer network in tough gels, a variety of ionic cross-linking biological polymers, including seaweed sodium (Sigma-Aldrich A2033)
Cross-linking with calcium sulfate ions (Sigma-Alginate C3771), chitosan (Sigma-Aldrich 448869)
Cross-linking with sodium triphosphate ion (Sigma-Aldrich 238503)
And sodium hyaluronic acid (Sigma-Aldrich H5542)
Cross-linking with iron chloride ions (Sigma-Aldrich 157740).
For benzone (for surface treatment of elastic materials)Sigma-Aldrich B9300)was used.
To visualize the pH change in the gel-elastic microfluid chip, universal pH indication solution (Sigma-Aldrich 36828)
Hydrogen chloride (Sigma-Aldrich 38280)
And sodium hydroxide (Sigma-Aldrich 795429)were used. Glucose (Sigma-Aldrich G8270)
Glucose enzymes (Sigma-Aldrich G7141)
In the test of the rubber surface treatment effect, it is used as an oxygen scavenger in the gel.
For rubber, Sylgard 184 (
Juzheng Dione; Dow Corning), Ecoflex (Smooth-On)Polyurethane (Smooth-On), latex (McMaster Carr)and VHB (3u2009M)were used. In the 90°-
Stripping test, high boron silicon glass (McMaster Carr)
Used as a rigid substrate bonded to the surface of the rubber bottom.
As a hard backing of the film, Pitt film (70u2009μm; ePlastics)
Used with propylene salts (Hangao Letai).
In the electric gel circuit experiment,Sigma-Aldrich 746398)
The solution is used as an electrolyte.
Drain coating for glass mold and lid, rain-X (ITW Inc. )
The solution was used.
The surface of the elastic body is treated by adsorption of benzone.
Thoroughly clean the elastic surface with methanol and deionized water, and completely dry with nitrogen before benzone treatment.
After that, the solution of benzone (10u2009wt. % in ethanol)
Uniform coverage of the entire elastic surface at room temperature for 2 min.
Then, wash three times with methanol and completely dry with nitrogen.
A gel with physical cross-linking was prepared by mixing a water pre-solution of 10 ml carefully degassedgel solution (12. 05u2009wt. % AAm, 1. 95u2009wt.
% Sodium algae and 0. 017u2009wt.
% PAAm of MBAA-
Seaweed gel; 18u2009wt. % AAm, 2u2009wt.
% Sodium hyaluronic acid and 0. 026u2009wt.
% PAAm of MBAA-
Hyaluronic acid gel; 24u2009wt. % AAm, 2u2009wt.
% Of sugar and 0. 034u2009wt.
% PAAm of MBAA-
Polymer gel; 20u2009wt. % PEGDA and 2. 5u2009wt.
Gelatin for peg da-
Seaweed gel; 20u2009wt.
% PEGDA and 2 rwWt.
% Sodium hyaluronic acid of PERDA-
Hyaluronic acid gel)
Cross joint with ion (
The concentration of calcium salt in PAAm is 20 × 10 u2009 m-
Seaweed gel;
The concentration of Iron Chloride in PAAm-is 3 × 10 µm
Hyaluronic acid gel;
The concentration of sodium trithing in PAAm-is 3 × 10 µm
Polymer gel;
Peg of 20 × 10 m-
Seaweed gel;
The concentration of Iron Chloride in PEGDA-is 3 × 10 µm
Hyaluronic acid gel)
And Irgacure 29590. 2u2009wt. %).
Quickly mix the mixture, pour it into the glass mold, and then cover it with a glass plate with a drain coating.
The gel is kept in a nitrogen chamber for 1 µh to form a physical cross-linking network.
Thereafter, the physically cross-linked gel is gently removed from the mold, assembled with a freshly processed elastic material, and then UV irradiation is performed in the UV chamber (
365 ultraviolet rays at nm; UVP CL-1000)
Within an hour, the PAAm network is bonded to the elastic surface by a bonded bond cross-bonding.
PAAm normal gel is a pre-degassing by direct curinggel solution (23u2009wt. % AAm, 0. 051u2009wt. % MBAA and 0. 2u2009wt. % Irgacure 2959)
On the elastic surface freshly treated inside the UV link agent.
The cross-linking conditions are the same as PAAm-
Seaweed gel.
Please note that the shear modulus of PAAm gel is adjusted to be with PAAm-
Modulus of seaweed gel (30u2009kPa)
Based on the data previously reported.
All tests were performed in ambient air at room temperature.
The gel and gel-elastic interface maintain consistent performance over test time (
That\'s about a few minutes)
During this period, the effect of dehydration was not significant.
The interface toughness of various gel-elastic mixtures was measured using standard 90 °-peeling test (ASTM D 2861)
With mechanical testing machine (
Load cell 2 kN or 20 µN; Zwick/Roell Z2. 5)and 90°-
Stripping fixture (
Test resources, G50).
All rubber substrate preparation month.
Width 5 cm, 7.
The length is 5 cm and the thickness is 1mm.
Adhesion of poly (DME) and Ecoflex to a boron silicon glass plate using oxygen plasma treatment (
Harrick plasma chip-001).
Glue the latex and polyurethane onto the glass plate with an epoxy adhesive.
VHB simply adheres to the glass plate because it is provided in two waysDouble sided tape form.
According to the procedure described above, the gel is glued to the elastic surface in a size of 100 × 15 × 3mm (
Long X wide x thick).
As a hard backing of the gel, the Pitt film is bonded to the gel with an acrylic adhesive.
Standard 90 ° for the resulting sample-
Stripping test was performed at a constant stripping speed of 50 min.
The measured Peel is up to a platform (
Slight oscillation)
Enter a stable state as the stripping process.
The interface toughness γ is determined by removing the platform force from the width of the film.
To investigate the effect of elastic surface treatment on the interface toughness and failure mode of the gel bonded on the elastic material, the same 90-
Peel test using PAAm-
Seaweed tough gel with the same sample size and test conditions and polyzhengdione substrate.
The surface treatment time of the polydione substrate was fixed at 2 min, while the concentration of benzone in the surface treatment solution changed from 2 wt. % to 10u2009wt. %. As PAAm-
The surface treatment solution containing