MSGID: 1:317/3 64a8e69c
PID: hpt/lnx 1.9.0-cur 2019-01-08
TID: hpt/lnx 1.9.0-cur 2019-01-08
 Chemists create the microspine with shape-transforming properties for
targeted cargo delivery at microscale 

  Date:
      July 7, 2023
  Source:
      The University of Hong Kong
  Summary:
      With the goal of advancing biomimetic microscale materials, the
      research team has developed a new method to create microscale
      superstructures, called MicroSpine, that possess both soft
      and hard materials which mimic the spine structure and can
      act as microactuators with shape-transforming properties. This
      breakthrough was achieved through colloidal assembly, a simple
      process in which nano- and microparticles spontaneously organize
      into ordered spatial patterns.


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FULL STORY
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In nature, it is common to find structures that combine both soft and
hard material. These structures are responsible for diverse mechanical
properties and functions of biological systems. As a typical example,
the human spine possesses alternating stacks of hard bones and soft
intervertebral discs, which is an essential architecture that supports the
human body while maintaining body flexibility. Mimicking the soft-hard
structure in nature can, in principle, inspire the design of artificial
materials and devices, such as actuators and robots. However, the
realisation has been extremely challenging, especially at the microscale,
where material integration and manipulation become exceedingly less
practical.

With the goal of advancing biomimetic microscale materials, the
research team led by Dr Yufeng WANG from the Department of Chemistry
of The University of Hong Kong (HKU) has developed a new method to
create microscale superstructures, called MicroSpine, that possess
both soft and hard materials which mimic the spine structure and
can act as microactuators with shape- transforming properties. This
breakthrough, published in the top scientific journal Science Advances,
was achieved through colloidal assembly, a simple process in which nano-
and microparticles spontaneously organise into ordered spatial patterns.

Many biological organisms, ranging from mammals to arthropods and
microorganisms, contain structures of synergistically integrated soft
and hard components. These structures exist in different lengths,
from micrometres to centimetres, and account for the characteristic
mechanical functions of biological systems. They have also stimulated
the creation of artificial materials and devices, such as actuators and
robots, which change shape, move, or actuate according to external cues.

Although soft-hard structures are easy to fabricate at the macroscale
(millimetre and above), they are much harder to realise at the microscale
(micrometre and below). This is because it becomes increasingly
challenging to integrate and manipulate mechanically distinct components
at smaller scale.

Traditional manufacturing methods, such as lithography, face several
limitations when attempting to create small-scale components using
top-down strategies. For example, low yield can occur because small-scale
manufacturing processes are more complex and require greater precision,
which can increase the risk of defects and errors in the final product.

To tackle the challenge, Dr Wang and his team took a different approach,
called colloidal assembly. Colloids are tiny particles 1/100 the size
of human hair and can be made from various materials. When properly
engineered, the particles can interact with one another, spontaneously
assembling into ordered superstructures. As a bottom-up method,
colloidal assembly is advantageous for making microscale structures
because it allows for precise control over the creation of the desired
structures from various building blocks, possessing a higher yield. Yet,
the difficulty is how to guide the particles to assemble to the desired
soft-hard structure.

By using the spine as a basis for design, the team has invented new
particles derived from metal-organic frameworks (MOFs), an emerging
material that can assemble with high directionality and specificity. Being
also the hard component, these MOF particles can combine with soft
liquid droplets to form linear chains. The hard and soft components
take alternating positions in the chain, mimicking the spine structure,
that is, the MicroSpine.

'We also introduce a mechanism by which the soft component of the chain
can expand and shrink when MicroSpine is heated or cooled, so it can
change shape reversibly,' explained Ms Dengping LYU, the first author of
the paper, as well as the PhD Candidate in the Department of Chemistry
at HKU.

Using the MicroSpine system, the team also demonstrated various precise
actuation modes when the soft parts of the chain are selectively
modified. In addition, the chains have been used for encapsulation and
release of guest objects, solely controlled by temperature.

The realisation of these functions is significant for the future
development of the system, as it could lead to the creation of intelligent
microrobots capable of performing sophisticated microscale tasks, such
as drug delivery, localised sensing and other applications. The highly
uniform and precisely structured microscale components could be used to
create more effective drug delivery systems or sensors that can detect
specific molecules with high sensitivity and accuracy.

The research team believes this technology represents an important step
towards creating complex microscale devices and machines. According to
Dr Wang, 'If you think about modern machinery such as cars, they are
assembled by tens of thousands of different parts. We aim to achieve
the same level of complexity using different colloidal parts.' By taking
inspiration from nature, the research team hopes to design more biomimetic
systems that can perform complex tasks at the microscale and beyond.

The research is funded by the Research Grants Council (RGC).

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Story Source: Materials provided by The_University_of_Hong_Kong. Note:
Content may be edited for style and length.


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Journal Reference:
   1. Dengping Lyu, Wei Xu, Nansen Zhou, Wendi Duan, Zhisheng Wang,
   Yijiang Mu,
      Renjie Zhou, Yufeng Wang. Biomimetic thermoresponsive
      superstructures by colloidal soft-and-hard co-assembly. Science
      Advances, 2023; 9 (26) DOI: 10.1126/sciadv.adh2250
==========================================================================

Link to news story:
https://www.sciencedaily.com/releases/2023/07/230707111635.htm

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