Whether it’s right under our nose or far away, when we observe an object we see it—provided we have healthy eyes and normal vision or suitable glasses—in focus. For this to work, muscles deform the lenses of our eyes and adjust them to a suitable focal distance.
For miniaturized technical devices, microscale lenses with a similar adaptable focus could be an advantage. In the journal Angewandte Chemie, Hong-Bo Sun and a team from Jilin University (China) have described a new approach to the production of adjustable microlenses made from protein gels.
Proteins are potentially useful as “building materials” for microcomponents because they are readily available, inexpensive, and biocompatible. They can also change their properties in response to external stimuli, which makes them an interesting material for use in adjustable microlenses. However, lenses must be extremely precise in order to meet optical requirements—something difficult to achieve with proteins. In addition, they must be fast, simple, and inexpensive to produce.
The Chinese researchers have now met this challenge: They used a laser to “write” the desired micrometer-sized lens shape out of a solution of bovine serum albumin, a protein. Methylene blue acts as a photosensitizer, which captures the light energy like an antenna and triggers a crosslinking reaction of the protein molecules. Driven by a computer, the laser cuts out the desired three-dimensional form voxel by voxel. A voxel is a three-dimensional pixel, a tiny segment of volume. The irradiation used is in femtosecond pulses, which lasts on the order of 10-13 seconds. The crosslinking reaction only takes place in the locations that are irradiated. After the reaction, the protein molecules that have not reacted can simply be rinsed away. What stays behind is a cross-linked, aqueous protein gel in the shapes of micrometer-sized lenses.
Direct writing with lasers usually results in structures that have too rough a surface for optical applications. By optimizing the duration of the laser pulse, the pulse intensity, and the protein concentration, Sun and his team obtained lenses with outstanding optical properties.
The special trick in this case is that the amount of liquid absorbed by the protein gel depends on the pH value of the solution. Increasing the pH causes the lens to swell. If the increase in thickness is limited by a glass surface, the lens primarily grows in width and becomes flatter. If the pH value is reduced, the gel shrinks and the lens is more curved. Because the radius of curvature determines the focal length of the lens, this method can be used to focus the microlenses.
Because the protein lenses are biocompatible, they may be used in optical analytical systems for medical diagnostics or lab-on-a-chip technology.About the Author
Hong-Bo Sun | Angewandte Chemie
Researchers target protein that protects bacteria's DNA 'recipes'
21.08.2018 | University of Rochester
Protein interaction helps Yersinia cause disease
21.08.2018 | Schwedischer Forschungsrat - The Swedish Research Council
There are currently great hopes for solid-state batteries. They contain no liquid parts that could leak or catch fire. For this reason, they do not require cooling and are considered to be much safer, more reliable, and longer lasting than traditional lithium-ion batteries. Jülich scientists have now introduced a new concept that allows currents up to ten times greater during charging and discharging than previously described in the literature. The improvement was achieved by a “clever” choice of materials with a focus on consistently good compatibility. All components were made from phosphate compounds, which are well matched both chemically and mechanically.
The low current is considered one of the biggest hurdles in the development of solid-state batteries. It is the reason why the batteries take a relatively long...
New design tool automatically creates nanostructure 3D-print templates for user-given colors
Scientists present work at prestigious SIGGRAPH conference
Most of the objects we see are colored by pigments, but using pigments has disadvantages: such colors can fade, industrial pigments are often toxic, and...
Scientists at the University of California, Los Angeles present new research on a curious cosmic phenomenon known as "whistlers" -- very low frequency packets...
Scientists develop first tool to use machine learning methods to compute flow around interactively designable 3D objects. Tool will be presented at this year’s prestigious SIGGRAPH conference.
When engineers or designers want to test the aerodynamic properties of the newly designed shape of a car, airplane, or other object, they would normally model...
Researchers from TU Graz and their industry partners have unveiled a world first: the prototype of a robot-controlled, high-speed combined charging system (CCS) for electric vehicles that enables series charging of cars in various parking positions.
Global demand for electric vehicles is forecast to rise sharply: by 2025, the number of new vehicle registrations is expected to reach 25 million per year....
17.08.2018 | Event News
08.08.2018 | Event News
27.07.2018 | Event News
21.08.2018 | Ecology, The Environment and Conservation
21.08.2018 | Life Sciences
21.08.2018 | Power and Electrical Engineering