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Updated: 12 hours 13 min ago

Very interesting review

Fri, 2022-09-30 23:53

In reply to Journal Club for October 2022: A Mechanical Approach to Shape, Flow, and Mechanoperception in Plants

Jean-François, thank you for discussing such an intriguing topic.  I enjoyed very much reading your brief review. 

Re: Great Summary

Sat, 2022-09-17 05:12

In reply to Great Summary

Dear Lifeng,

Many thanks for your kind words and comments!  Please see my replies below:

1. The booming of the light-based 3D techniques has attracted lots of attention in the precise fabrication of active-soft network materials at different length scales.  For instance, Prof. Qi Ge's group has used the digital light processing (DLP) based 3D-printing technique to fabricate shape-memory polymers (SMPs), liquid crystal elastomer (LCE), and hydrogel-based active soft network materials at microscale, where the width of microstructure ranges from 100 μm to 1 mm (see Advanced Materials, 2021, 33: 2101298; Advanced Materials, 2020, 32: 2000797; Science Advances, 2021, 7: eaba4261).  Prof. Rayne Zeng’s group used the projection stereolithography systems to fabricate the polymer-based soft network piezoelectric materials, where the width of microstructure is around 100 μm (see Natural Materials, 2019, 18: 234).  Buckling-guided 3D assembly could also be exploited to transform 2D active network materials into well-ordered 3D structures (see Nature Communications, 2022, 13: 524).

2. Existing studies showed the possibility of forming soft network materials with ordered microstructure in nano/micro-scale through electrospinning technique.  For example, the fixed metallic receiver always resulted in randomly distributed microstructures, due to the irregular spraying, but if the fixed receiver turns to the rotated metallic receiver, the aligned nano/micro-scale fibers can be obtained (see Advanced Materials Interfaces, 2022, 9: 2101808; ACS Applied Materials Interfaces, 2021, 13: 26339).  To obtain ordered nano/microstructures with more complex geometries, it might still remain challenging. 

Warm regards!


Great Summary

Thu, 2022-09-15 11:25

In reply to Journal Club for September 2022: Mechanics of soft network materials

Dear Yihui,

Thanks for this excellent and timely discussion. I am involved in some studies in 2D soft network materials and believe that these materials have remarkable futures. I have some thoughts in this topic.

1) To be active - soft network materials in response to various external stimuli. There are many active materials available in bulk material state, and are there any convenient methods to structure them in to a network state at different length scale? 

2) Randomly distributed vs highly ordered - To have well controlled macroscopic material properties, clearly highly-ordered network materials are desired. Electrospinning provides a convenient way to fabricate randomly distributed network materials in mesoscale. Is it possible to convert them into highly ordered nano-/micro-structures?  


Best wishes,



A new machine learning-based

Tue, 2022-09-13 02:54

In reply to Problem-independent machine learning (PIML)-based topology optimization—A universal approach

A new machine learning-based approach for topology optimization

 Problem-independent machine

Tue, 2022-09-13 02:53

In reply to Problem-independent machine learning (PIML)-based topology optimization—A universal approach

 Problem-independent machine learning (PIML)-based topology optimization—A universal approach


Tue, 2022-09-13 02:53

In reply to Problem-independent machine learning (PIML)-based topology optimization—A universal approach


Problem-independent machine learning (PIML)-based topology optimization—A universal approach

आण तुझ्या पहिल्या बाजीरावाला माझ्यासमोर!

Mon, 2022-09-12 19:17

In reply to Pune unnecessarily has too many private universities, don't you think so?

आण तुझ्या पहिल्या बाजीरावाला माझ्यासमोर!

तो चांगला होता, उदय आर्मी कुलकर्णी! अन्, तू मला Structural Length and Breadth of Shaniwar WaDaa बद्दल उत्तर नाही दिलस मूर्खा Indian Army वाल्या ब्राम्हणा! Leftanant Curnal / Curnal / Brigedier/ etc.

आण तुझ्या पहिल्या बाजीरावाला माझ्यासमोर!

बघून घेतो त्याला पण अन् तुला पण! उदय आर्मी कुलकर्णी!



OK, uploaded

Mon, 2022-09-12 16:50

In reply to Shrikant Datar and Thite you take this

OK, uploaded my CV.

Shrikant Datar and Thite you take this

Mon, 2022-09-12 16:45

In reply to Also Thite of Pune Times of India

Shrikant Datar,


You explain to me why I didn't make money, when your beloved Savitri Mumukshu did.


You take this, together with your beloved Savitri Mumukshu.


[I am attaching my CV from the [recent] times when I went jobless and she minted money to buy home in your fucked up San Francisco Bay Area.





Also Thite of Pune Times of India

Mon, 2022-09-12 16:23

In reply to Shrikant Datar Loves Savitri Mumukshu

Also Thite of Pune Times of India

Tarunaai is the word which most became famous under his authorship.

Tarunaai laa naachaayalaa aavaData. Rastyaata. Hospital madhale mele tar chaalatil. Tarunaai naachate. Tarunaai. Tarunaai. Tarunaai. Thite. Ma Ta. Ma Ta. Ma Ta. Tarunaai.

Shrikant Datar Loves Savitri Mumukshu

Mon, 2022-09-12 16:21

In reply to Pune unnecessarily has too many private universities, don't you think so?

Shrikant Datar Loves Savitri Mumukshu [^]

She can't post her own paintings or share her own CV or reveal her own name to any one on the 'net. Because, she was born to love and enjoy riches.

I had posted my own paintings and had made my own Web site and had posted my paintings and thoughts on grades and rankings and all on that Web site before I even signed up here or at my blog at

Jaggi Ayyangar and Shrikant Datar both love Savitri Mumukshu.

What to do?



Re: Homogeneous vs. heterogeneous

Sat, 2022-09-10 19:49

In reply to Homogeneous vs. heterogeneous

Dear Zheng,

Thank you so much for your comments and insightful questions!  Engineering heteogeneous soft network materials is a very important direction in this area.  While I did not mention the heteogeneous designs in this summary, there are already some explorations reported in the literature.  Regarding the biomimetic soft network materials, the heteogeneous designs can be exploited to better reproduce the spatially non-uniform mechanical properties of skins (Nature Communications, 2015, 6: 6566), noting that the human skin actually has gradient mechanical responses (e.g., nearby waist).  Regarding the soft mechanical metamaterials, introducing heteogenous bi-material horseshoe microstructure design can enable unusual modes of thermal expansion, such as thermally-induced shearing and bending (Advanced Materials, 2019, 31, 1905405).  Regarding the practical applications related to stretchable inorganic electronics, the heteogeneous designs can be exploited to achieve a better integration with the complexly patterned electrical interconnects and hard chips (Science Advances, 2022, 8, eabm3785). 

In terms of the fabrication of heteogeneous soft network materials, the photolithographic processes for creating the 2D networks can easily afford access to gradient forms of the microstructure with spatially varying values of the widths of the ribbon microstructures.  I totally agree it is more challenging to fabricate 3D heteogeneous networks.  You may refer to my reply to Prof. Dong Wang's 2nd comment.

Warm regards!


Homogeneous vs. heterogeneous

Sat, 2022-09-10 12:50

In reply to Journal Club for September 2022: Mechanics of soft network materials

Dear Yihui,

Thank you very much for putting together this nice and timely topic of soft network materials. This is a very informative and fascinating summary! I have one question: Most soft network materials, especially 3D soft network materials, are homogeneous; That is, the lattice structure or pattern is the same throughout the material. Is it possible to design and fabricate heterogeneous soft network materials that impart different material properties (e.g. Young's modulus) to different regions of the soft network material? Will that enable new functions of soft network materials?

Thank you in advance.






Dear Dong,

Sat, 2022-09-10 09:18

In reply to 3D lattice and large stretchability

Dear Dong,

Many thanks for your kind words and questions!  Please see my replies below:

1. In comparison to 2D couterparts, the 3D lattice metamaterials involve much more complex geometries and complicated deformation modes, which makes the development of quantitative mechanics model and design method more challenging.  Despite these difficulties, several important achievements have been made regarding the design of 3D lattice metamaterials, aside from the aforementioned work.  For instance, Prof. Qiming Wang’s group developed a mechanics model of elastomer lattices in the finite deformation regime (see Journal of the Mechanics and Physics of Solids, 2022, 159: 104782), and Prof. Mohsen Asle Zaeem’s group developed a constitutive thermo-visco-hyperelastic model to analyze the shape-memory behavior of several SMP octet-truss lattices (see International Journal of Mechanical Sciences, 2022, 232: 107593).  The main difficulty in their fabrication is elaborated in the reply to your second comment.

2. Indeed, the lack of general, high-resolution 3D fabrication techniques applicable to a very broad range of material types represents a key challenge.  Two/multi-photon lithography, stereolithography technique, digital light processing (DLP) technique and nozzle-based 3D printing techniques correspond to a few promising fabrication techniques of 3D lattice metmaterials.  Excluding the two/multi-photon lithography, the other techniques can all be used in the fabrication of soft lattice metamaterials.  For instance, Prof. Jinsong Leng’s group, Prof. Qi Ge's group (in collaboration with Prof. Yakacki) and Prof. Qiming Wang’s group already employed the laser cladding deposition (LCD), digital light processing (DLP) technique, and stereolithography technique to fabricate SMP lattice metamaterials (see Advanced Functional Materials, 2020, 30: 2004226), LCE lattice metamaterials (see Advanced Materials, 2020, 32: 2000797), and elastomer-based lattice metamaterials (see Journal of the Mechanics and Physics of Solids, 2022, 159: 104782), respectively.  For the modeling approaches, both micromechanics and phenomenological models show promising potentials to guide the design of soft lattice metamaterials.

Warm regards!


3D lattice and large stretchability

Thu, 2022-09-08 23:28

In reply to Journal Club for September 2022: Mechanics of soft network materials

Dear Prof. Zhang,

Very stimulating post! Really outstanding work! I have a few questions.

(1) Work on 3D lattice metamaterials is still rare. What are the main difficulties in fabrication and design?

(2) The materials used in lattice metamaterials generally have a low fracture strain. Lattice metamaterials constructed using softer materials with larger stretchabilities are promising. But it poses challenges to fabrications and modeling. What are the potential approaches?

Thank you. 

Best regards, Dong Wang

Reply to Tongqing's questions

Wed, 2022-09-07 07:46

In reply to Dear Yihui,

Dear Tongqing,

Many thanks for your kind words and inspiring questions! Please see my replies below:

1. It would be very interesting to explore soft network designs that can combine the physical attributes of both biomimetic materials and metamaterials.  Some progress has been made by introducing soft active materials (e.g., SMP, LCE and hydrogels) into network designs for development of mechanical metamaterials that offer, simultaneously, biomimetic mechanical properties (e.g., J-shaped stress-strain curves and flaw-insensitive behavior) and exotic mechanical behavior (e.g., negative Poisson’s ratios, unusual swelling responses, negative thermal expansion, and abnormal acoustic properties).  For example, my group developed a class of soft network metamaterials by exploiting horseshoe-shaped composite microstructures of hydrogel and passive materials as building blocks, which showed both large negative swelling responses and J-shaped stress-strain curves (see Science Advances, 2018, 4: eaar8535).  The mechanics-guided designs consisting of zigzag microstructures could also endow network materials with both J-shaped stress-strain curves and isotropic negative Poisson’s ratios at large strains (see Soft Matter, 2018, 14:693).

2. The fatigue performance of soft network materials should be important to consider, especially in practical applications.  Intuitively, their fatigue performances mainly depend on the mechanical properties of the constituent materials.  As such, if fatigue-resistant materials are exploited to fabricate the network structures, then the fatigue performance of the entire soft network should be good as well.  The fatigue behavior of the soft network materials embedded in anti-fatigue hydrogels is also worthy of further exploration. 

Warm regards!


Dear Yihui,

Tue, 2022-09-06 04:53

In reply to Journal Club for September 2022: Mechanics of soft network materials

Dear Yihui,

Really appreciate for sharing your profound and original insights into this emerging field of soft materials. Soft network materials can be designed to reproduce the J-shaped stress-strain curves of soft tissues, as well as to offer unusual mechanical properties that differ from natural materials. I have two questions

1. Is that possible to design a type of soft network materials with combining attributes of biomimetic materials and metamaterials?

2. Since I have been working on fatigue of soft materials, I wonder if the fatigue performance of such soft network materials is good or not.

Thank you.



Network imperfections

Sun, 2022-09-04 06:26

In reply to Network imperfections

Hi Teng,

Many thanks for your insightful questions! Please see my replies below:

1. Yes, the soft tissues in biology are typically composed of randomly distributed networks.  The 'J-shaped' nonlinear stress-strain curves of randomly distributed networks are usually not as sharp as that of periodically distributed networks - the tangential modulus of periodically distributed networks increases more rapidly than the network with randomness, as the strain increases.  This is because the transition of bending-dominated deformation to stretching-dominated one is more abrupt in periodically distributed networks.

2. My group has not studied the fracture toughness or crack propagation in soft network materials.  But we did analyze the stress concentration in soft network materials with circular-hole imperfections (i.e., with a certain number of missing horseshoe microstructures, depending on the hole size in relative to the microstructure size) (see ACS Applied Materials & Interface, 2019, 11: 36100-3610; Acta Mechanica Sinica, 2021, 37: 1050-1062).  Both the size and location of the circular-hole imperfections are shown to have profound influences on the stretchability of the network.  But the factor of stress-concentration is usually much smaller than the case in 2D solid materials. 

3. Missing microstructures, manufacturing imperfections (unequal sizes or material defects), notchs and cracks can be regarded as different types of flaws.  In addition to the aforementioned hole-type imperfections, Prof. Norman A. Fleck's group has studied the influence of manufacturing imperfections and notch sensitivities on the mechanical responses of lattice materials consisting of wavy microstructures in comparison to those with straight microstructures (see International Journal of Mechanical Sciences, 2019, 192: 106137; JAM, 2021, 88: 031011).  The soft networks with wavy microstructures are found to be more imperfection insensitive than corresponding lattice materials with straight microstructures in most cases.  Along this direction, it might be interesting to introduce the tools of topology optimization or machine learning to design soft network materials with further enhanced flaw insensitivity.

Warm regards!


Network imperfections

Sat, 2022-09-03 13:33

In reply to Journal Club for September 2022: Mechanics of soft network materials

Hi Yihui,

Thanks a lot for your excellent summary of this very exciting field! The engineered nonlinear stress-strain curve is very impressive. I have a few questions related to newtwork imperfections:

(1) As you mentioned that some of the studies are inspired by biological networks, those structures are also less regular and may have some random distribution of the network. How will this affect the modulus of your designed structures?

(2) If the network imperfections are too large, they become flaws/cracks. Did you study the fracture toughness and crack propagation in the soft network structures? 

(3) Many biological structures are designed to be flaw insensitive, which is determined by the mechanical properties and sample sizes. Will you be able to engineer flaw insensitive soft newtwork structures?




Fri, 2022-08-26 12:14

In reply to Freely jointed chain models with extensible links

Nice and interesting work

Lots of new work are referenced in this area


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