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Nature Electronics covers the study
2084, and even though you're nearly 100 years old, anti-aging medications keep your skin firm and energized
.
At this time, the brain-computer interface technology is quite mature, through which you control your stock trading account
with your mind.
Maybe this is a science fantasy, can life really connect with electronics? Life is soft, but machines are hard
.
Traditional electronic devices, hard and dry, may cause an immune response
in the human body.
Repulsion and connection
.
For example, steel nails after fractures, implanted teeth, these most common implants, the human body may produce rejection
.
For example, cochlear implants, even soft materials such as silicone, may have rejection reactions, edema, tenderness or itching
.
On December 18, 2013, an artificial heart was implanted into the chest cavity of a 76-year-old
Frenchman.
It was the world's first artificial heart transplant, and despite some rejection-resistant materials, the artificial heart stopped beating after 75 days due to a "circuit short circuit.
"
Faced with the "embarrassment" of electronic devices entering the body, Hydrogel has high hopes because it has both soft toughness and good biocompatibility
.
If you're a foodie, gelatinous substances you're familiar with — jelly, cold skin, tofu, pearls
in bubble tea.
Hydrogel is everywhere, it can be a contact lens, or it can be a crystal mud
for children to play with.
Technically, hydrogels are three-dimensional networks
formed by chemical or physical crosslinking of hydrophilic polymer chains.
It can fully absorb water without being soluble in water, has a soft texture, physical properties similar to biological tissues, and has good biocompatibility
.
Traditional hydrogel electronic devices are generally divided into two parts: hydrogel matrix and metal circuits and electronic components, in layman's terms, that is, hydrogel to "wrap and package" the circuit
.
However, in the core circuit part, hard metal
is still used.
Another way, Zhou Nanjia's research team's breakthrough this time is precisely to "unify" the metal part into a hydrogel state, turning hard into soft
.
The team looked for a breakthrough in the design method of the material, and found a calcium alginate-polyacrylamide double-network hydrogel to modify
.
Calcium alginate-polyacrylamide double-network hydrogel is a commonly used hydrogel
with high tensile properties and high toughness.
Sodium alginate can form ionic crosslinking with calcium ions, while the polyacrylamide network is covalently
crosslinked by acrylamide monomer and crosslinker.
Covalent crosslinking can be understood as bonding by sharing electrons, which is a very strong way
.
.
The hydrogel conductive ink enables good covalent crosslinking with the surrounding hydrogel support substrate for ultra-high stretchability
.
In this way, all components of hydrogel electronics are soft, including the circuit part and the matrix part
.
All of these materials, before 3D printing, were fluids, and after printing, acrylamide covalently polymerized in the hydrogel matrix by heat initiating the covalent polymerization of acrylamide in the hydrogel matrix can obtain an integrated hydrogel electronic device
encapsulated with internal circuitry.
A "soft heart" that is soft for life must be able to go through layers of tests
.
In order to verify the actual effect of this method, Zhou Nanjia's team "carefully" made some experimental models to verify
.
The team first prepared two-dimensional inductors with different turns and three-dimensional solenoid inductors with different diameters, and the electrical properties of the prepared hydrogel inductor devices were basically consistent with the analog values at a test frequency of 200 kHz, which proved that this method has the ability to
make fine circuits.
The team then experimented with printing a chip hydrogel inductor that would wirelessly light up a red LED bead and still work
when stretched.
In addition, RFID (radio frequency identification, a contactless data communication) hydrogel device can also be obtained
by embedded 3D printing.
By wirelessly lighting the red LED lamp beads
, the flexible circuit can still work under stretching In order to further verify the high degree of automation of the embedded 3D printing developed, the team used the industry's commonly used pick-and-place method to place the active LED device into the hydrogel support matrix, and realized three-dimensional inductive printing directly connected to the LED - that is, printing a conductive coil, and using the electromagnetic field to receive energy, generate voltage, and make the LED emit light
.
By surface modifying the active LED device, the entire device can produce strong covalent crosslinking that can maintain effective operation
under the condition of 100 tensile and compressive large strains.
.
Due to the good flexibility of the hydrogel matrix and ink, the electronic conductive part of the hydrogel electrode can be directly applied to the surface of human skin, which can effectively reduce the impedance, so that the 3D printed electrode shows higher resolution
than the traditional commercial electrode.
The "ultimate goal" of this method is to make a direct "connection" with living organisms, and this has also been very successful in mouse experiments
.
The experimental team prepared a fully hydrogel electrode that could be used to provide electrical stimulation that could be surgically wound on
the sciatic nerve of mice.
Under pulsed voltage stimulation at a frequency of 1Hz, the 3D printed electrode can cause regular, large-angle movements of the mouse's legs at voltages as low as 100mV.
The electrode of the control ionically conductive hydrogel can barely trigger the tiny movement
of the mouse's legs under the action of a driving voltage of 250mV.
Compared with the "hard and cold" metal electrode in the mouse experiment, the "soft" strategy of Zhou Nanjia's team is more eye-catching
.
From the initial idea to the final technical realization, the research team walked for almost two years
.
The reason for the different breakthroughs is inseparable
from the research team's long-term accumulation of hydrogel materials and 3D printing manufacturing methods.
Hui Yue, a postdoctoral fellow at Westlake University and the first author of this paper, said that this set of technical methods can play an important role
in the field of personalized customization of implantable electronic devices.
Perhaps in 2084, the electronic instruments connected to your life are soft and warm, and the source of technology is in a breakthrough and attempt in 2022
.
END*The co-corresponding authors of this paper are Nanjia Zhou and Tao Liang, PI of Westlake University, Hui Yue, postdoctoral fellow, and the co-first author is Yao Yuan
, assistant researcher of Westlake University.
Special thanks to the Public Experimental Platform
of Material Science at Westlake University.
The research results, titled "Three-dimensional printing of soft hydrogel electronics", were published in the early morning of December 20, 2022 in the form of a cover article.
on
Nature Electronics.
The first is the School of Engineering, Westlake University, Zhejiang Provincial Key Laboratory of 3D Micro-Nano Processing and Characterization Research, and the Future Industry Research Center of Westlake University, and all the authors are from Westlake University
.
2084, and even though you're nearly 100 years old, anti-aging medications keep your skin firm and energized
.
At this time, the brain-computer interface technology is quite mature, through which you control your stock trading account
with your mind.
Maybe this is a science fantasy, can life really connect with electronics? Life is soft, but machines are hard
.
Traditional electronic devices, hard and dry, may cause an immune response
in the human body.
Soft hydrogels are considered to be the best candidates to solve this problem, but there is still a lack of a method
that can efficiently construct customizable flexible circuits in hydrogel substrates.
This time, Westlake University fundamentally proposed a new idea, so that the electronic device part can also be as soft as hydrogel and freely printed
.
Developed by Nanjia Zhou's team at Westlake University, the technology includes a hydrogel support matrix and a silver-hydrogel composite conductive ink
.
Model of the hydrogel circuit in print
Repulsion and connection
The history of human beings as living beings connecting with the outside world is a painful and tortuous history
.
At the Osteopathic Museum in Oklahoma, there is a 2,000-year-old skull of a Peruvian warrior, and a metal plate was implanted in the bone, perhaps from an injury repair, when humans wanted to use external materials to "repair" the human body
.
A Peruvian samurai skull implanted with a metal block
"Foreign" materials will be recognized by the human body, resulting in a certain rejection reaction.
For example, steel nails after fractures, implanted teeth, these most common implants, the human body may produce rejection
.
For example, cochlear implants, even soft materials such as silicone, may have rejection reactions, edema, tenderness or itching
.
On December 18, 2013, an artificial heart was implanted into the chest cavity of a 76-year-old
Frenchman.
It was the world's first artificial heart transplant, and despite some rejection-resistant materials, the artificial heart stopped beating after 75 days due to a "circuit short circuit.
"
Faced with the "embarrassment" of electronic devices entering the body, Hydrogel has high hopes because it has both soft toughness and good biocompatibility
.
If you're a foodie, gelatinous substances you're familiar with — jelly, cold skin, tofu, pearls
in bubble tea.
Hydrogel is everywhere, it can be a contact lens, or it can be a crystal mud
for children to play with.
Technically, hydrogels are three-dimensional networks
formed by chemical or physical crosslinking of hydrophilic polymer chains.
It can fully absorb water without being soluble in water, has a soft texture, physical properties similar to biological tissues, and has good biocompatibility
.
Traditional hydrogel electronic devices are generally divided into two parts: hydrogel matrix and metal circuits and electronic components, in layman's terms, that is, hydrogel to "wrap and package" the circuit
.
However, in the core circuit part, hard metal
is still used.
Another way, Zhou Nanjia's research team's breakthrough this time is precisely to "unify" the metal part into a hydrogel state, turning hard into soft
.
The team looked for a breakthrough in the design method of the material, and found a calcium alginate-polyacrylamide double-network hydrogel to modify
.
Calcium alginate-polyacrylamide double-network hydrogel is a commonly used hydrogel
with high tensile properties and high toughness.
Sodium alginate can form ionic crosslinking with calcium ions, while the polyacrylamide network is covalently
crosslinked by acrylamide monomer and crosslinker.
Covalent crosslinking can be understood as bonding by sharing electrons, which is a very strong way
.
Calcium alginate-polyacrylamide double-network hydrogels have strong tensile toughness
However, the previously commonly used methods, calcium alginate and polyacrylamide, are synthesized into a whole hydrogel by one-step method, which lacks flexibility
.
The research team divided the solidification of these two hydrogels into two independent steps - first solidifying calcium alginate, and then "breaking" and refining into microgel microparticles
.
In addition to calcium alginate, this gel particle also contains acrylamide monomer, crosslinking agent and free radical initiator, with a particle size of about 20 microns, which can be used as 3D printing "ink"
.
After printing, the heating initiates the curing of the polyacrylamide to finalize the electronics
.
Freely print circuits in a hydrogel matrix that has not yet cured
Microgel particles are fluid and can be used to print the "matrix" of electronic devices, so can they be modified so that such microgel particles can conduct electricity and be used to print the circuit parts of electronic devices? It sounds a bit whimsical, but the process of exploring it next is even more magical
.
After trial and error, the team found a breakthrough point – mixing microgel particles with a small number of micron silver flakes and additives to make a conductive ink material
.
In fact, the research team has tried many times about the mixing ratio of micron silver sheets and microgel particles, as well as other additives, and finally found an optimal ratio
.
This conductive hydrogel ink can freely construct a flexible circuit
with a three-dimensional structure in the matrix of microgel particles by embedded printing.
Under an electron microscope, micron silver sheets are distributed like capillaries in the gaps between the microgel particles, forming a soft 3D network in which electric current flows
freely.
Since the silver sheet is mainly confined to the interface of the hydrogel microparticles, the conductivity of the ink can be as high as 1.
4x103S/cm
.
.
The hydrogel conductive ink enables good covalent crosslinking with the surrounding hydrogel support substrate for ultra-high stretchability
.
In this way, all components of hydrogel electronics are soft, including the circuit part and the matrix part
.
All of these materials, before 3D printing, were fluids, and after printing, acrylamide covalently polymerized in the hydrogel matrix by heat initiating the covalent polymerization of acrylamide in the hydrogel matrix can obtain an integrated hydrogel electronic device
encapsulated with internal circuitry.
A "soft heart" that is soft for life must be able to go through layers of tests
.
In order to verify the actual effect of this method, Zhou Nanjia's team "carefully" made some experimental models to verify
.
The team first prepared two-dimensional inductors with different turns and three-dimensional solenoid inductors with different diameters, and the electrical properties of the prepared hydrogel inductor devices were basically consistent with the analog values at a test frequency of 200 kHz, which proved that this method has the ability to
make fine circuits.
The team then experimented with printing a chip hydrogel inductor that would wirelessly light up a red LED bead and still work
when stretched.
In addition, RFID (radio frequency identification, a contactless data communication) hydrogel device can also be obtained
by embedded 3D printing.
By wirelessly lighting the red LED lamp beads
, the flexible circuit can still work under stretching In order to further verify the high degree of automation of the embedded 3D printing developed, the team used the industry's commonly used pick-and-place method to place the active LED device into the hydrogel support matrix, and realized three-dimensional inductive printing directly connected to the LED - that is, printing a conductive coil, and using the electromagnetic field to receive energy, generate voltage, and make the LED emit light
.
By surface modifying the active LED device, the entire device can produce strong covalent crosslinking that can maintain effective operation
under the condition of 100 tensile and compressive large strains.
The pick-and-place method places the active LED device into the hydrogel support matrix
.
Due to the good flexibility of the hydrogel matrix and ink, the electronic conductive part of the hydrogel electrode can be directly applied to the surface of human skin, which can effectively reduce the impedance, so that the 3D printed electrode shows higher resolution
than the traditional commercial electrode.
The "ultimate goal" of this method is to make a direct "connection" with living organisms, and this has also been very successful in mouse experiments
.
The experimental team prepared a fully hydrogel electrode that could be used to provide electrical stimulation that could be surgically wound on
the sciatic nerve of mice.
Under pulsed voltage stimulation at a frequency of 1Hz, the 3D printed electrode can cause regular, large-angle movements of the mouse's legs at voltages as low as 100mV.
The electrode of the control ionically conductive hydrogel can barely trigger the tiny movement
of the mouse's legs under the action of a driving voltage of 250mV.
Compared with the "hard and cold" metal electrode in the mouse experiment, the "soft" strategy of Zhou Nanjia's team is more eye-catching
.
From the initial idea to the final technical realization, the research team walked for almost two years
.
The reason for the different breakthroughs is inseparable
from the research team's long-term accumulation of hydrogel materials and 3D printing manufacturing methods.
Hui Yue, a postdoctoral fellow at Westlake University and the first author of this paper, said that this set of technical methods can play an important role
in the field of personalized customization of implantable electronic devices.
Perhaps in 2084, the electronic instruments connected to your life are soft and warm, and the source of technology is in a breakthrough and attempt in 2022
.
END*The co-corresponding authors of this paper are Nanjia Zhou and Tao Liang, PI of Westlake University, Hui Yue, postdoctoral fellow, and the co-first author is Yao Yuan
, assistant researcher of Westlake University.
Special thanks to the Public Experimental Platform
of Material Science at Westlake University.
The research results, titled "Three-dimensional printing of soft hydrogel electronics", were published in the early morning of December 20, 2022 in the form of a cover article.
on
Nature Electronics.
The first is the School of Engineering, Westlake University, Zhejiang Provincial Key Laboratory of 3D Micro-Nano Processing and Characterization Research, and the Future Industry Research Center of Westlake University, and all the authors are from Westlake University
.
