Capability of Sputtered Micro-patterned NiTi Thick Films

Bechtold, Christoph; Miranda, Rodrigo Lima de; Quandt, Eckhard

doi:10.1007/s40830-015-0029-9

Cited by 17 publications

(21 citation statements)

References 23 publications

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“…. In addition to flat films, complex geometries adapted to the cooling application, such as perforated membranes or tube geometries are possible designs for devices using a heat transfer fluid . Film dimensions within this Review have a thickness in the range of 20–30 μm, a width between 0.5 and 3 mm, and a length ranging from 5 to 30 mm.…”

Section: Elastocaloric Films—overview and Advancesmentioning

confidence: 99%

“…Structural fatigue can often be minimized by using an adequate fabrication technique such as magnetron sputtering in combination with subsequent surface polishing. As a result, carbide inclusions and voids acting as nucleation centres for cracks can be avoided . Mechanical‐ or electropolishing on the other hand smooths sharp edges.…”

Section: Elastocaloric Films—overview and Advancesmentioning

confidence: 99%

“…Thel atter enables,i n combination with UV lithographya nd wet chemical etching, free-standing films with at hickness up to 80 mma nd as mall feature size.D etails about the processing steps can be found in Ref. [34].I na ddition to flat films,c omplex geometries adapted to the cooling application, [35] such as perforated membraneso rt ube geometriesa re possible designsf or devices using ah eat transfer fluid. [34,35] Film dimensions within this Review have at hickness in the range of 20-30 mm, a width between 0.5 and3mm, and al ength ranging from 5t o 30 mm.…”

Section: Materials and Fabricationmentioning

confidence: 99%

“…[34].I na ddition to flat films,c omplex geometries adapted to the cooling application, [35] such as perforated membraneso rt ube geometriesa re possible designsf or devices using ah eat transfer fluid. [34,35] Film dimensions within this Review have at hickness in the range of 20-30 mm, a width between 0.5 and3mm, and al ength ranging from 5t o 30 mm. Even though similar shapes/geometries are possible using cold rolling, in combination with laser structuring or magnetron sputtering using UV lithography,d ifferences exist on the microstructural scale.C old rollingi nvolves the thickness reduction of an already-crystallized material, whereas magnetron-sputtered films are,i nt he as-deposited state,f ully amorphous.…”

Section: Materials and Fabricationmentioning

confidence: 99%

“…[1][2][3] Caloric effects such as magneto-, electro-, and mechanocaloric effects do not rely on refrigerants contributingt og lobal warminga nd potentially reach large temperature changes DT and/or high cooling power. [4][5][6] Large elastocaloric effects near room temperature structural phase transitions have been observed,f or instance,i nc opper-based shape-memory alloys (SMAs) showing DT up to 15 K [7] and in Ti-Ni-based alloys revealing the largestt emperature changes DT of 15-40 K. [8,9] Thel atent heat can reach up to 35 Jg À1 in Ti-Nibased alloys. [10,11] In these materials,t he elastocaloric effect is based on as tress-induced reversible phase transformation between the high-temperature phase austenite( A) and the low-temperaturep hase martensite (M).…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Elastocaloric Cooling on the Miniature Scale: A Review on Materials and Device Engineering

Bruederlin

Bumke²,

Chluba³

et al. 2018

Energy Tech

Self Cite

104

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This Review covers the fundamentals of operation and scaling of elastocaloric cooling devices as well as current developments of elastocaloric shape‐memory alloy (SMA) films and the engineering of SMA film‐based cooling devices. Sputter‐deposited TiNiCuCo alloys showing ultra‐low fatigue enable unique functional properties such as tailored transformation temperature gradients. Two substantially different concepts for the development of elastocaloric cooling demonstrators are discussed. One concept relies on heat transfer by mechanical contact between the elastocaloric SMA film and solid heat sink and source elements. The second concept makes use of the heat transfer between the elastocaloric SMA film and a heat transfer fluid, including the advanced technology of active regeneration. Demonstrators based on a single SMA film reach device temperature spans of 14 K and a high specific cooling power of up to 18 W g−1. The performance characteristics are compared with other solid‐state caloric cooling technologies.

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Section: Elastocaloric Films—overview and Advancesmentioning

confidence: 99%

Section: Elastocaloric Films—overview and Advancesmentioning

confidence: 99%

Section: Materials and Fabricationmentioning

confidence: 99%

Section: Materials and Fabricationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Elastocaloric Cooling on the Miniature Scale: A Review on Materials and Device Engineering

Bruederlin

Bumke²,

Chluba³

et al. 2018

Energy Tech

Self Cite

104

View full text Add to dashboard Cite

show abstract

Thin‐Film Patient‐Specific Flow Diverter Stents for the Treatment of Intracranial Aneurysms

Velvaluri

Pravdivtseva

Berg

et al. 2021

Adv Materials Technologies

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Intracranial aneurysm treatment based on blood flow reduction with braided flow diverters (FDs) has become highly relevant. However, FDs have several limitations, e.g., sudden torsional collapse, variable porosity, and possible side branch occlusions. Thin‐film FD stents can overcome these limitations by offering high design freedom to produce patient‐specific implants. Here a workflow to design, fabricate, and characterize novel thin‐film FDs that can be individualized to meet patient‐specific needs is demonstrated. FD design is virtually optimized to achieve the best flow reduction and the lowest crimping resistance. Then, the optimal design is fabricated using state‐of‐the‐art thin‐film technology. The thin‐film FD is characterized for mechanical and flow behavior and is compared to a braided FD (Derivo; FD0). The thin‐film FD and FD0 show similar radial forces in the diameter range 2.6–4.5 mm, and the former exhibits no sudden torsional collapse. The flow analysis using MRI reveals that both FDs reduce the flow into the aneurysm. However, only the thin‐film FD maintains adequate flow into all the side branches. A thin‐film FD that overcomes braided FDs limitations while offering similar performance has been developed. The proposed framework is a pilot study for fabricating on‐demand patient‐specific thin‐film FD stents.

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Shape Memory Alloy Thin Film Auxetic Structures

Dengiz

Goldbeck

Curtis

et al. 2023

Adv Materials Technologies

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Auxetic structures provide an interesting approach to solving engineering problems due to their negative Poisson's ratio, which allows for elongation perpendicular to applied stresses, opposite to a conventional structure's necking behavior. Thus, they can function well in applications requiring compacting the device into a small volume during the deployment (e.g., implants inserted with catheters) or stretchability with area coverage (e.g., stretchable electronics). Fabricating them with shape memory alloys (SMAs) expands the possibilities. The high strains experienced by auxetic structures may become reversible compared to ordinary metals due to superelastic or shape memory effect. This work studies four different auxetic microstructures using thin film SMAs that are capable of surviving strains up to 57.4%. Since these structures are fabricated by layer deposition and lithography, other components, such as microelectronics, can be seamlessly integrated into the fabrication process. These auxetic thin films are investigated for their mechanical behavior under tension for their stretchability and stability. Under tension, thin films are known to show wrinkling instabilities. In two of four designs, the large auxetic behavior leads to wrinkling, while the other two display stable, non‐wrinkling behavior. These designs can be candidates for stretchable electronics, wearable medical devices (e.g., biosensors), or implants (e.g., stents).

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Capability of Sputtered Micro-patterned NiTi Thick Films

Cited by 17 publications

References 23 publications

Elastocaloric Cooling on the Miniature Scale: A Review on Materials and Device Engineering

Elastocaloric Cooling on the Miniature Scale: A Review on Materials and Device Engineering

Thin‐Film Patient‐Specific Flow Diverter Stents for the Treatment of Intracranial Aneurysms

Shape Memory Alloy Thin Film Auxetic Structures

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