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Updated: 5 hours 28 min ago

Strong adhesion between soft materials

Sun, 2018-12-02 12:20

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Dear Qihan and Hyunwoo:  Thank you both for discussing this topic of great depth and immediacy.  Adhering soft materials has been hard. The newly discovered methods achieve strong adhesion between soft materials.  These methods have opened an enormous field of opportunity for invention and discovery. I look forward to seeing many more researchers in this field participate in this discussion.   

Adhesion between hydrogels and diverse substrates

Sun, 2018-12-02 12:02

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Dear qihan and hyunwoo,

 

Thanks for the nice organization and pioneering works. I have tried all the adhesion methods above. And I want to discuss some issues with you.

(1) To achieve tough bonding between hydrogels and diverse substrates, previous methods usually rely on two strong interactions at the interface. The first is covalent bonding at the interface including silane method, EDC-NHS chemistry (Li, Science, 2017) and benzophenone chemistry. The second is the topological entanglement including glue method and topohesion (Yang, Advanced Materials, 2018) Can there be another kind of interfacial interaction to achieve tough adhesion?

(2) For cured polymer networks, topological entanglement is a better method without requiring functional groups of the polymer networks. However, the present method requires a long working time (Yang, Advanced Materials, 2018) or is toxic (Wirthl, Science Advances, 2017). What’s a better solution?

Thank you very much!

 

Topology of wet adhesion

Sun, 2018-12-02 12:01

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Dear Qihan,

Thank you for bringing up this interesting yet extremely important research topic. In your brief review of the recent efforts, the promising and fruitful future of this field is foreseen. Here, I would like to add my personal opinions to the discussion.

One clear disadvantage of thses bonding methods is that they (except cyanoacrylate whose mechanism is unclear) rely on the design of the chemistry of bonds to achieve strong adhesion. The hydrogel and the elastomer need to have matching functional groups to form bonds. However, design chemistry of bonds either on the surface or in the bulk may cause many complications: 1, surface modification is inconvenient; 2, bulk modification changes the origical mechanical properties of materials; 3, in some bonding situations, such as inside body, surface and bulk modification is impossible; 4, beyond elastomer, the chemistry of bonds limits the choice of materials.

Our group recently discover a new aspect in wet adhesion--the topolgy of connecting materials. By a topology we mean a type of connectivity through bonds, chains, particles, networks, or their combinations. Significantly, numrous topologies are possible, but not explored. Creating bonds is just one of the topology. Two examples of topologies are following:

1. A stitch-stitch topology [1]

This topology does not require fucntional groups from both materials. We spread polymer chains at the interface of two polymer networks, and trigger them to form a new polymer network in situ, localzied at the interface, in topological entanglement with both preexisting polymer networks, stiching them together like a suture.

 

2. A bond-bond topology [2]

We use polymer chains to form covalent bonds with both polymer networks.

 

Reference

[1]. Yang, Jiawei, Ruobing Bai, and Zhigang Suo. "Topological adhesion of wet materials." Advanced Materials 30.25 (2018): 1800671.

[2]. Li, J., Celiz, A. D., Yang, J., Yang, Q., Wamala, I., Whyte, W., ... & Mooney, D. J. (2017). Tough adhesives for diverse wet surfaces. Science, 357(6349), 378-381.

Glass Phase Works for Adhesion

Sun, 2018-12-02 11:00

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Dear Qihan, 

Nice organization of adhesion topics. As your opinion for glue, we already proved that the glass phase plays an important role in the adhesion of polymer. Potentially a widely useful technology. We show some surprising results for hydrogels. The paper will come soon.

Thanks Hyunwoo! These are

Sat, 2018-12-01 22:49

In reply to Dear Qihan,

Thanks Hyunwoo! These are truly the pioneering works that inspired all the following works on the bonding between hydrogels and elastomers!

Dear Qihan,

Sat, 2018-12-01 17:55

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Dear Qihan,

 

Thank you for initiating the discussion on this nascent topic in soft materials. It is truly inspiring and well-summarizing the recent developments on this important topic. I would like to add a few points to facilitate the discussion.

 

The mechanism for tough bonding of hydrogels was reported in 2015 by Yuk et al [1]:

a. Tough and dissipative hydrogel matrix to prevent cohesive failure and provide dissipation to enhance interfacial toughness.

b. Strong linkages between hydrogels and bonded materials to provide high intrinsic interfacial toughness.

Figure 1. Mechanism for tough bonding of hydrogels by synergies between interfacial linkages and bulk dissipation [1].

 

We also developed a cohesive-zone and Mullins-effect model [1, 2] to quantitatively illustrate the mechanism and reported a method for tunable adhesion from 1Jm-2 to 1,000 Jm-2.

Figure 2. Tunable adhesion ranging from 1 to 1,000 Jm-2 by controlling interfacial linkage density via surface modification (silanization time here) [2].

 

Following the above-mentioned mechanism, we proposed the concept of robust hydrogel-elastomer hybrid in 2016 [3]. Since then, many applications that harnessed the merits of hydrogels and elastomers are rapidly emerging. A few examples from our group:

 

a. Anti-dehydration hydrogels, where an elastomer coating on hydrogels can prevent their dehydration [3].

b. Living materials and devices, where the hydrogel provides a matrix for living cells and the elastomer skin to prevent dehydration of the material and devices [3,4].

c. Robust hydrogel coatings, where tough hydrogels provide soft, wet and slippery coatings on existing elastomer devices such as medical gloves, tubings and even condoms [5,6]. 

d. Hydraulic hydrogel robots that are acoustically and optically transparent in water yet fast and forceful enough to catch live fishes [7].

 

References

[1] Hyunwoo Yuk, Teng Zhang, Shaoting Lin, German Alberto Parada, Xuanhe Zhao*, Tough bonding of hydrogels to diverse non-porous surfaces, Nature Materials 15, 190-196 (2016)

[2] Teng Zhang#, Hyunwoo Yuk#, Shaoting Lin, Xuanhe Zhao*, Tough and tunable adhesion of hydrogels: experiments and models, ​Acta Mechanica Sinica 33​, 543-554 (2017)

[3] Hyunwoo Yuk, Teng Zhang, German Alberto Parada, Xinyue Liu, Xuanhe Zhao*, Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures, Nature Communications 7, 12028 (2016)

[4] Xinyue Liu#, Tzu-Chieh Tang#, Eléonore Tham#, Hyunwoo Yuk#, Shaoting Lin, Timothy K. Lu*, Xuanhe Zhao*, Stretchable living materials and devices with hydrogel-elastomer hybrids hosting programmed cells, PNAS 114, 2200-2205 (2017)

[5] German A. Parada, Hyunwoo Yuk, Xinyue Liu, Alex J. Hsieh, Xuanhe Zhao*, Impermeable robust hydrogels via hybrid lamination, Advanced Healthcare Materials 6, 1700520 (2017)

[6] Yan Yu#, Hyunwoo Yuk#, German A. Parada#, You Wu, Xinyue Liu, Kamal Youcef-Toumi, Xuanhe Zhao*, Multifunctional hydrogel skins on diverse polymers with arbitrary shapes, Advanced Materials, in press (2018)

[7] Hyunwoo Yuk, Shaoting Lin, Chu Ma, Mahdi Takaffoli, Nicholas X. Fang, Xuanhe Zhao*, Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water, Nature Communications 8, 14230 (2017)

Thank you for great article!

Sat, 2018-12-01 13:52

In reply to Journal Club for December 2018: Bonding hydrophilic and hydrophobic soft materials for functional soft devices

Dear Qihan, Thank you for initiating the discussion on this nascent topic in soft materials. It is truly inspiring and well-summarizing the recent developments on this important topic. I would like to add a few points to facilitate the discussion. The mechanism for tough bonding of hydrogels was reported in 2015 by Yuk et al [1]: a. Tough and dissipative hydrogel matrix to prevent cohesive failure and provide dissipation to enhance interfacial toughness.b. Strong linkage between hydrogels and bonded materials to provide high intrinsic interfacial toughness. Figure 1. Mechanism for tough bonding of hydrogels by synergies between interface and bulk dissipation [1]. We also developed a cohesive-zone and Mullins-effect [2] to quantitatively illustrate the above-mentioned mechanism and reported a method for tunable adhesion from 1Jm-2 to 1,000 Jm-2. Figure 2. Tunable adhesion ranging from 1 to 1,000 Jm-2 by controlled surface modification (silanization time here) [2]. Following the above-mentioned mechanism, We proposed the concept of robust hydrogel-elastomer hybrid in 2016 [3]. Since then, many applications that harness the merits of hydrogels and elastomers are rapidly emerging. A few examples from our group: a. Anti-dehydration hydrogelswhere an elastomer coating on hydrogels to prevent their dehydration [3]. b. Living materials and devices, where the hydrogel provides a matrix for living cells and the elastomer skin to prevent dehydration of the material and devices [3,4]. c. Robust hydrogel coatings, where tough hydrogels provide soft, wet and slippery coatings on existing elastomer devices such as medical gloves, tubings and even condoms [5,6].  d. Hydraulic hydrogel robots that are acoustically and optically transparent in water yet fast and forceful enough to catch live fishes [7]. References[1] Hyunwoo Yuk, Teng Zhang, Shaoting Lin, German Alberto Parada, Xuanhe Zhao*, Tough bonding of hydrogels to diverse non-porous surfaces, Nature Materials 15, 190-196 (2016)[2] Teng Zhang#, Hyunwoo Yuk#, Shaoting Lin, Xuanhe Zhao*, Tough and tunable adhesion of hydrogels: experiments and models, ​Acta Mechanica Sinica 33​, 543-554 (2017)[3] Hyunwoo Yuk, Teng Zhang, German Alberto Parada, Xinyue Liu, Xuanhe Zhao*, Skin-inspired hydrogel-elastomer hybrids with robust interfaces and functional microstructures, Nature Communications 7, 12028 (2016)[4] Xinyue Liu#, Tzu-Chieh Tang#, Eléonore Tham#, Hyunwoo Yuk#, Shaoting Lin, Timothy K. Lu*, Xuanhe Zhao*, Stretchable living materials and devices with hydrogel-elastomer hybrids hosting programmed cells, PNAS 114, 2200-2205 (2017)[5] German A. Parada, Hyunwoo Yuk, Xinyue Liu, Alex J. Hsieh, Xuanhe Zhao*, Impermeable robust hydrogels via hybrid lamination, Advanced Healthcare Materials 6, 1700520 (2017)[6] Yan Yu#, Hyunwoo Yuk#, German A. Parada#, You Wu, Xinyue Liu, Kamal Youcef-Toumi, Xuanhe Zhao*, Multifunctional hydrogel skins on diverse polymers with arbitrary shapes, Advanced Materials, in press (2018)[7] Hyunwoo Yuk, Shaoting Lin, Chu Ma, Mahdi Takaffoli, Nicholas X. Fang, Xuanhe Zhao*, Hydraulic hydrogel actuators and robots optically and sonically camouflaged in water, Nature Communications 8, 14230 (2017)

Thank you very much Dr. Xu.

Wed, 2018-11-28 08:06

In reply to Somnath Congratulation !

Thank you very much Dr. Xu.

Thank you Dr. Buryachenko. I

Wed, 2018-11-28 08:06

In reply to Somnath,

Thank you Dr. Buryachenko. I appreciate this.

 

Somnath Congratulation !

Tue, 2018-11-27 19:39

In reply to 2019 Ted Belytschko Applied Mechanics Award – Professor Somnath Ghosh

Look forward to meeting you at AMD dinner in 2019!

Roy

Somnath,

Mon, 2018-11-26 20:06

In reply to 2019 Ted Belytschko Applied Mechanics Award – Professor Somnath Ghosh

Somnath,

Congratulations on a great recognition of your contribution into computational micromechanics

interesting book, and interesting attempt

Mon, 2018-11-26 13:36

In reply to non-equilibrium thermodynamic methods in tribology

dear Michael, an interesting book full of ideas. I have downloaded a copy for free at http://b-ok.cc/book/2365963/4dfe32

I am not in a position to judge much of it, except the many parts where you collect more standard results in friction dynamics like TEI or Adams instability with Coulomb friction.

When you move to review Soviet-time ideas on entropy, I generally loose you, as probably I don't know much of these attempts. Have they led anywhere?

But I would need also to check carefully all your results, before I can use them.  For example, just after (3.45)

"In other words, if the coefficient of friction increases with the sliding velocity, the system is unstable."

 

This is generally the opposite of what you find normally true. There is a huge literature against this.  Are you sure of this result?

 

non-equilibrium thermodynamic methods in tribology

Mon, 2018-11-26 10:03

In reply to Is Tribology Approaching Its Golden Age? Grand Challenges in Engineering Education and Tribological Research

Thank you for interesting and educational papers... I agree with most of these concepts, in particular, with the importance of the thermodynamic approach... I personally think (for many years) that given friction is a dissipative process, it is desirable to deduce frictional properties from the Second Law of Thermodynamics and from non-equlibrium thermodynamics principles... Several years ago, we had a book where we tried to address some of these matters, but

M. Nosonovsky & V. Mortazavi. Friction-Induced Vibrations and Self-Organization: Mechanics and Non-Equilibrium Thermodynamics of Sliding Contact (CRC Press/Taylor & Francis, 2013) 

 

Offer/position is CLOSED

Sun, 2018-11-25 23:58

In reply to PhD Position: 3D Printing

Offer/position  is CLOSED

Big congratulations!

Sat, 2018-11-24 14:37

In reply to 2019 Ted Belytschko Applied Mechanics Award – Professor Somnath Ghosh

Big congratulations for well-deserved recognition, Somnath!

The Position is Closed

Thu, 2018-11-22 09:36

In reply to Research Position Computational Fracture Mechanics

Dear All,

The position is closed now.

Do not apply for the post anymore.

 

with regards,

Abhishek

Addition

Wed, 2018-11-21 09:17

In reply to What is the physical meaning of Green-Lagrangian strain and Eulerian-Almansi strain measures?

Hi Selvam,

Do you want to share your findings with us?

Nice work!

Mon, 2018-11-19 16:06

flexoelectricity enables domain at 800 °C

Mon, 2018-11-19 09:16

In reply to Journal Club for November 2018: Beyond piezoelectricity: Flexoelectricity in solids

Hello Jiawang,

We recently found domain-like nanoregions (DLNRs) up to an extreme temperature of 800 °C in a NBT-25ST core–shell nanoparticles by TEM. By applying electric field to the nanoparticles in temperature-dependent in-situ TEM, the change of DLNRs indicates a polorizaiton-switching-like behavior. By combing the TEM observation and phase-field simulation including flexoelectricity, we found that the DLNRs at extreme temperature is possibly attributed to the flexoelectricity which is originated from the strain gradient induced by the diffusion of strontium cations at high temperatures.

Ref:

Enabling nanoscale flexoelectricity at extreme temperature by tuning cation diffusion. Nature Communicationsvolume 9, Article number: 4445 (2018)

https://www.nature.com/articles/s41467-018-06959-8

 

All the best,

Min

Dear Jiawang,

Thu, 2018-11-15 15:10

In reply to  

Dear Jiawang,

Thank you for your interest on our works. I would also like to share our recent work published in Physical Review Letters. In this paper, we have shown that piezoelectricity can indeed imitate flexoelectricity on the condition that the piezoelectric coefficient is inhomogeneously and asymmetrically distributed across the sample. If this condition is met, asymmetric piezoelectricity becomes indistinguishable from intrinsic flexoelectricity in single cantilever-bending experiments. Our calculations show that, for standard perovskite ferroelectrics, even a tiny gradient of piezoelectricity (1% variation of piezoelectric coefficient across 1 mm) is sufficient to yield a giant effective flexoelectric coefficient of 1 μC/m, three orders of magnitude larger than the intrinsic expectation value. This mimicry complicates the task of interpreting experimental results although we have suggested some approaches to separate inhomogeneous piezoelectricity from flexoelectricity.

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.121.205502

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