Shape memory materials and technology
Wearable applications
Comparison of shape memory effect and shape change effect
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Plastic bag
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SMA (Nitinol)
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Comparison of elastic sponge, memory foam and shape memory foam
Free energy
(different energy barrier between State A and State B) |
Elastic sponge and memory foam: shape change effect
Shape memory foam: shape memory effect Ref: Thermo/chemo-responsive shape memory effect in polymers: a sketch of working mechanisms, fundamentals and optimization, Journal of Polymer Research, Vol. 19, No. 9, 2012, 9952 Emma X BASF｜生活节奏不被定义，慢回弹将你还给自己。
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Comparison of elastic, memory and shape memory insolesElastic insole and memory insole: shape change effect
Shape memory insole: shape memory effect |
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Environmental temperature dependent:
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Comparison of two elastic glasses frames:
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Ref: Stimulus-responsive shape memory materials: a review, Materials and Design, 33, 577-640
An introduction to shape memory materials |
Online version
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Shape memory materials |
Short version
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Stimulus-responsive shape memory materials: a review |
Long version (a summary of what I have done before 2012)
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(a) Original shape; (b) programmed shape; (c) after shape recovery
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Basic working mechanisms for the SME in polymeric materials(I) Dual-state mechanism (DSM);
(II) Dual-component mechanism (DCM); (III) Partial-transition mechanism (PTM). (a) Original sample at room temperature; (b) Upon heating and compressing; (c) After cooling and constraint removal; (d) After heating for shape recovery. Thermo/chemo-responsive shape memory effect in polymers: a sketch of working mechanisms, fundamentals and optimization, Journal of Polymer Research, Vol. 19, No. 9, 2012, 9952
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Ref：Chapter 2: Overview shape memory materials. In: Sokolowski WM, editor. Cold hibernated elastic memory structure: self-deployable technology and its applications. New York: CRC Press; 2019.
Three phases, six transformations (left) and change in lattice structure (right).
Ref: Thermomechanical behavior of shape memory alloys under non-proportional load. In: Proceedings of SPIE on transducing materials and devices; 2002 October 31. SPIE; 2002. p. 183–91
Ref: Shape change/memory actuators based on shape memory materials, Journal of Mechanical Science and Technology, 31(10), 2017, 4863-4873
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Characterization of shape memory performance |
Programming strain (shaft dimension and sample thickness) and programming temperature dependent.
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Previous version
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Uniaxial tension/compression mode |
Ideally, we should use uniaxial tension/compression mode.
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(a)-(c): programming (short term shape fixity ratio)
(c)-(d): creeping/relaxation (long term shape fixity ratio) (d)-(e): recovery (shape recovery ratio) |
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Ref: Characterization of polymeric shape memory materials, Journal of Polymer Engineering, Vol. 37, 2017, 1-20
Bending mode |
(ignore creeping/relaxation)
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Twisting mode |
(ignore creeping/relaxation)
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- To enable the shape memory effect in materials.
- To design a material with the required shape memory function. - To optimize the shape memory performance. |
环境响应型高分子：种类、原理及应用进展
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Multi-dimensional memory in low-friction granular materials
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Soft Matter, 2025, 21, 4890
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记忆效应的工作原理是什么？
AI阅读
引用颗粒材料的记忆效应是指材料对其过去变形历史的依赖性，这种依赖性会影响其对未来变形的响应。其工作原理主要涉及以下几个方面：
1. 颗粒重排：
颗粒材料的记忆效应源于颗粒重排和塑性变形，这些改变会导致材料内部结构发生永久改变，从而使材料能够记忆其过去变形历史，并影响其对未来变形的响应。
AI阅读
引用颗粒材料的记忆效应是指材料对其过去变形历史的依赖性，这种依赖性会影响其对未来变形的响应。其工作原理主要涉及以下几个方面：
1. 颗粒重排：
- 当颗粒材料受到变形时，颗粒之间的接触力和排列方式会发生变化，导致颗粒重排。
- 这些颗粒重排是非可逆的，即使变形停止，颗粒也无法完全恢复到原始位置，从而导致材料内部结构发生永久改变。
- 颗粒重排会导致材料发生塑性变形，即材料在受到外力作用时会发生永久性的形变。
- 塑性变形的程度取决于变形的幅度、速率和材料的特性等因素。
- 随着颗粒材料经历多次相同的变形，颗粒重排会变得更加可重复，导致材料在相同的变形下更容易发生形变。
- 这种对过去变形历史的记忆效应，使得材料能够在未来变形中表现出不同的力学行为。
- 当颗粒材料再次受到与过去相同的变形时，材料会更容易发生形变，并表现出与过去变形历史相关的特征。
- 这种记忆读取过程可以用于检测材料的变形历史，或者用于开发新型传感器和执行器。
- 颗粒材料的特性： 颗粒材料的摩擦系数、形状、尺寸、硬度等因素都会影响颗粒重排和塑性变形，从而影响记忆效应。
- 变形的类型和幅度： 不同的变形类型（例如，剪切、压缩、拉伸）和幅度都会导致不同的颗粒重排和塑性变形，从而影响记忆效应的类型和强度。
- 训练的顺序： 训练的顺序会影响颗粒材料内部结构的改变，从而影响其记忆能力。
- 环境因素： 环境因素，例如温度、湿度等，也会影响颗粒材料的记忆效应。
颗粒材料的记忆效应源于颗粒重排和塑性变形，这些改变会导致材料内部结构发生永久改变，从而使材料能够记忆其过去变形历史，并影响其对未来变形的响应。
（和形状记忆材料DSC下的温度记忆效应非常相似）
Sun L, Wang TX, Huang WM, Monitoring minor over-heating/cooling temperature based on the temperature memory effect in shape memory materials via differential scanning calorimetry: A brief review of the recent progress, Journal of Thermal Analysis and Calorimetry, 133, 2018, 1649-1661
Sun L, Wang TX, Huang WM, Monitoring minor over-heating/cooling temperature based on the temperature memory effect in shape memory materials via differential scanning calorimetry: A brief review of the recent progress, Journal of Thermal Analysis and Calorimetry, 133, 2018, 1649-1661
———————— 智谱清言
在外界激励的作用下，系统从一个状态变化到另一各状态。其中的变化，有一部分可能是可以在撤去激励后自动恢复的，一部分可以在施加反向激励恢复，一部分是永久的。对应于形状记忆材料，比如形状记忆聚合物，分别是弹性的变形，可恢复的形状记忆变形和永久变形。是否可以这样理解？本文所述的记忆效应，与形状记忆聚合物一致。
AI阅读
引用您的理解是正确的，可以将颗粒材料的记忆效应与形状记忆聚合物的不同变形类型进行类比：
颗粒材料的记忆效应：
本文主要研究的是颗粒材料的可恢复的形状记忆变形，即颗粒材料在经历多次相同的变形后，会形成记忆，并在相同的变形下更容易发生形变。这种记忆效应与形状记忆聚合物的可恢复形状记忆变形一致。
需要注意的是：
颗粒材料的记忆效应与形状记忆聚合物的记忆效应在本质上是一致的，都表现出对历史状态的依赖性。但两者在形成机制和应用方式上存在差异。
AI阅读
引用您的理解是正确的，可以将颗粒材料的记忆效应与形状记忆聚合物的不同变形类型进行类比：
颗粒材料的记忆效应：
- 弹性变形： 在外界激励（例如，剪切、压缩）作用下，颗粒材料会发生形变，但当激励撤去后，材料可以自动恢复到原始状态。这类似于形状记忆聚合物的弹性变形。
- 可恢复的形状记忆变形： 在外界激励作用下，颗粒材料会发生塑性变形，形成记忆。当施加反向激励（例如，反向剪切、反向压缩）时，材料可以恢复到记忆状态。这类似于形状记忆聚合物的可恢复形状记忆变形。
- 永久变形： 在外界激励作用下，颗粒材料会发生不可逆的塑性变形，导致材料内部结构发生永久改变，无法恢复到原始状态。这类似于形状记忆聚合物的永久变形。
本文主要研究的是颗粒材料的可恢复的形状记忆变形，即颗粒材料在经历多次相同的变形后，会形成记忆，并在相同的变形下更容易发生形变。这种记忆效应与形状记忆聚合物的可恢复形状记忆变形一致。
需要注意的是：
- 颗粒材料的记忆效应与形状记忆聚合物的记忆效应在形成机制上有所不同。颗粒材料的记忆效应源于颗粒重排，而形状记忆聚合物的记忆效应源于材料内部微观结构的改变。
- 颗粒材料的记忆效应可以应用于更广泛的领域，例如自适应材料、形状记忆材料等，而形状记忆聚合物主要用于形状改变相关的应用。
颗粒材料的记忆效应与形状记忆聚合物的记忆效应在本质上是一致的，都表现出对历史状态的依赖性。但两者在形成机制和应用方式上存在差异。
Under the action of external stimuli, the system changes from one state to another. Some of the changes can be automatically restored after removing the stimuli, some can be restored by applying reverse stimuli, and some are permanent. Corresponding to shape memory materials, such as shape memory polymers, they are elastic deformation, recoverable shape memory deformation, and permanent deformation. Can this be understood in this way? The memory effect described in this paper is consistent with that of shape memory polymers.
AI: Your understanding is correct. The memory effect of granular materials can be compared with the different types of deformation of shape memory polymers:
Memory Effect of Granular Materials:
This paper mainly studies the recoverable shape memory deformation of granular materials, that is, granular materials form memory after experiencing multiple cycles of the same deformation, and are more likely to deform under the same deformation. This memory effect is consistent with the recoverable shape memory deformation of shape memory polymers.
It should be noted that:
The memory effect of granular materials and the memory effect of shape memory polymers are essentially the same, both exhibiting dependence on historical state. However, there are differences in their formation mechanisms and application methods.
AI: Your understanding is correct. The memory effect of granular materials can be compared with the different types of deformation of shape memory polymers:
Memory Effect of Granular Materials:
- Elastic Deformation: Under the action of external stimuli (e.g., shear, compression), granular materials will deform, but when the stimuli are removed, the material can automatically return to its original state. This is similar to the elastic deformation of shape memory polymers.
- Recoverable Shape Memory Deformation: Under the action of external stimuli, granular materials will undergo plastic deformation and form memory. When reverse stimuli (e.g., reverse shear, reverse compression) are applied, the material can return to the memory state. This is similar to the recoverable shape memory deformation of shape memory polymers.
- Permanent Deformation: Under the action of external stimuli, granular materials undergo irreversible plastic deformation, resulting in permanent changes in the material’s internal structure, which cannot be restored to the original state. This is similar to the permanent deformation of shape memory polymers.
This paper mainly studies the recoverable shape memory deformation of granular materials, that is, granular materials form memory after experiencing multiple cycles of the same deformation, and are more likely to deform under the same deformation. This memory effect is consistent with the recoverable shape memory deformation of shape memory polymers.
It should be noted that:
- The memory effect of granular materials and the memory effect of shape memory polymers differ in their formation mechanisms. The memory effect of granular materials originates from particle rearrangements, while the memory effect of shape memory polymers originates from changes in the microscopic structure of the material.
- The memory effect of granular materials can be applied to a wider range of fields, such as adaptive materials, shape memory materials, etc., while shape memory polymers are mainly used for shape change-related applications.
The memory effect of granular materials and the memory effect of shape memory polymers are essentially the same, both exhibiting dependence on historical state. However, there are differences in their formation mechanisms and application methods.
Stokes flow (named after George Gabriel Stokes), also named creeping flow or creeping motion,[1] is a type of fluid flow where advective inertial forces are small compared with viscous forces.[2] The Reynolds number is low, i.e. Re≪1. This is a typical situation in flows where the fluid velocities are very slow, the viscosities are very large, or the length-scales of the flow are very small. Creeping flow was first studied to understand lubrication. In nature, this type of flow occurs in the swimming of microorganisms and sperm.[3] In technology, it occurs in paint, MEMS devices, and in the flow of viscous polymers generally.
Time-reversibility
An immediate consequence of instantaneity, time-reversibility means that a time-reversed Stokes flow solves the same equations as the original Stokes flow. This property can sometimes be used (in conjunction with linearity and symmetry in the boundary conditions) to derive results about a flow without solving it fully. Time reversibility means that it is difficult to mix two fluids using creeping flow.
An immediate consequence of instantaneity, time-reversibility means that a time-reversed Stokes flow solves the same equations as the original Stokes flow. This property can sometimes be used (in conjunction with linearity and symmetry in the boundary conditions) to derive results about a flow without solving it fully. Time reversibility means that it is difficult to mix two fluids using creeping flow.
Demonstration of time-reversibility
A Taylor–Couette system can create laminar flows in which concentric cylinders of fluid move past each other in an apparent spiral.[14] A fluid such as corn syrup with high viscosity fills the gap between two cylinders, with colored regions of the fluid visible through the transparent outer cylinder. The cylinders are rotated relative to one another at a low speed, which together with the high viscosity of the fluid and thinness of the gap gives a low Reynolds number, so that the apparent mixing of colors is actually laminar and can then be reversed to approximately the initial state. This creates a dramatic demonstration of seemingly mixing a fluid and then unmixing it by reversing the direction of the mixer.[15][16][17]
A Taylor–Couette system can create laminar flows in which concentric cylinders of fluid move past each other in an apparent spiral.[14] A fluid such as corn syrup with high viscosity fills the gap between two cylinders, with colored regions of the fluid visible through the transparent outer cylinder. The cylinders are rotated relative to one another at a low speed, which together with the high viscosity of the fluid and thinness of the gap gives a low Reynolds number, so that the apparent mixing of colors is actually laminar and can then be reversed to approximately the initial state. This creates a dramatic demonstration of seemingly mixing a fluid and then unmixing it by reversing the direction of the mixer.[15][16][17]
