Periodic Reporting for period 2 - SWISSMODICS (Development of a Sensor with WIde Spectrum Sensitivity for MOnitoring of Damage and Defects In Composite Structures)
Berichtszeitraum: 2022-01-01 bis 2023-11-30
In the EU-funded Clean Sky project SWISSMODICS, coordinated by CSEM, experts have designed an image sensor for integration into aircraft composite structures. This innovation aims to identify damage and defects, streamlining inspections and minimizing the need for prolonged downtimes or disassembly of aircraft.
Aircraft undergo regular inspections, both as part of routine maintenance and after experiencing impacts, such as those from ground support equipment at airport gates or in-flight bird strikes. The impact damage on an aircraft's structure may not always be visible at the point of contact.
That’s especially true for aircraft made from composite materials, which are increasingly common as composites weigh less than conventional materials. When a composite material is impacted, that creates a shock wave that propagates through the material and may cause damage – called delamination – at a location distant from the impact site making the damage harder to detect.”
A variety of methods are available for detecting delamination in composites. However, they involve inspections that require aircraft to be grounded for long periods of time or even disassembled – both of which are costly processes.
In SWISSMODICS, three partner organizations – CSEM, Jean Monnet University in Saint-Etienne, France, and Almay Technologies in Chauvigny, France, – have developed a broad-wavelength spectrum image sensor , while ensuring a slim profile enabling a seamless integration directly into the aircraft’s composite structure to detect damage. This new technology could substantially shorten inspection times and reduce the inconvenience caused to both airlines and passengers, especially when planes must be grounded at the last minute for unplanned maintenance inspections.
The new device was designed to detect a broad spectrum of wavelengths: visible, X-ray and infrared. Operators can select the most suitable range from three options to effectively detect damage or inspect specific areas
The sensor includes an electronic chip containing an array of 512 x 512 pixels on which different types of sensitive layers (quantum dots / perovskite) have been deposited, to be sensitive to X-ray, visible and short-wave infrared up to 1300 nm. This is to our knowledge the worldwide first CMOS X-ray sensor with direct conversion in quantum dots. It not only detects X-ray photons, but also visible light and infrared light up to a wavelength of 1300 nm. The sensor was used successfully to detect defects in composite samples. The project, completed in November 2023, showcased a wide-spectrum sensor with outstanding X-ray detection capabilities. The very high absorption coefficient of the detecting layer enables thin X-ray detectors, which is key for their incorporation in composite structures. The use of standard processes to deposit these layers will enable the development of low cost sensors, that support not only the development of lighter aircraft, with all the environmental benefits that will bring, but will also benefit other markets outside the aeronautical one.
Aircraft undergo regular inspections, both as part of routine maintenance and after experiencing impacts, such as those from ground support equipment at airport gates or in-flight bird strikes. The impact damage on an aircraft's structure may not always be visible at the point of contact.
That’s especially true for aircraft made from composite materials, which are increasingly common as composites weigh less than conventional materials. When a composite material is impacted, that creates a shock wave that propagates through the material and may cause damage – called delamination – at a location distant from the impact site making the damage harder to detect.”
A variety of methods are available for detecting delamination in composites. However, they involve inspections that require aircraft to be grounded for long periods of time or even disassembled – both of which are costly processes.
In SWISSMODICS, three partner organizations – CSEM, Jean Monnet University in Saint-Etienne, France, and Almay Technologies in Chauvigny, France, – have developed a broad-wavelength spectrum image sensor , while ensuring a slim profile enabling a seamless integration directly into the aircraft’s composite structure to detect damage. This new technology could substantially shorten inspection times and reduce the inconvenience caused to both airlines and passengers, especially when planes must be grounded at the last minute for unplanned maintenance inspections.
The new device was designed to detect a broad spectrum of wavelengths: visible, X-ray and infrared. Operators can select the most suitable range from three options to effectively detect damage or inspect specific areas
The sensor includes an electronic chip containing an array of 512 x 512 pixels on which different types of sensitive layers (quantum dots / perovskite) have been deposited, to be sensitive to X-ray, visible and short-wave infrared up to 1300 nm. This is to our knowledge the worldwide first CMOS X-ray sensor with direct conversion in quantum dots. It not only detects X-ray photons, but also visible light and infrared light up to a wavelength of 1300 nm. The sensor was used successfully to detect defects in composite samples. The project, completed in November 2023, showcased a wide-spectrum sensor with outstanding X-ray detection capabilities. The very high absorption coefficient of the detecting layer enables thin X-ray detectors, which is key for their incorporation in composite structures. The use of standard processes to deposit these layers will enable the development of low cost sensors, that support not only the development of lighter aircraft, with all the environmental benefits that will bring, but will also benefit other markets outside the aeronautical one.
The project was divided into 6 work packages (WP). Here is a brief description of each WP:
WP1 - configuration and requirement definition
The functional and operational requirements of the sensor to be developed have been established, as well as the definition of the physical, electrical and mechanical interfaces of the system. The types of defects to be detected has also been defined, composite structures incorporating such defects have been fabricated to serve as references.
WP2 - Preliminary evaluation of the sensing technology
Starting from the requirements established in WP1, the system specifications and the sensor specifications have been derived, in particular the spectral range which must cover X-ray, visible and near infrared photons. For this purpose, two types of materials have been investigated, perovskite and sol-gel and optimized to extend their sensitivity in the near infrared band. Perovskite enables direct conversion from photon to electrical charges, while the use of sol-gel leads to an indirect conversion from near-infrared photons to visible photons. Patterning of different kind of perovskite materials was also studied to selectively optimize pixels for a specific spectral range (X-ray, visible or near infrared). Both technologies achieved near infrared sensitivity. Due to its high conversion efficiency, high X-ray absobtion coeffcicient and long term interesting perspectives, perovskite was retained as the material to be used for the demonstrator.
WP3 – Design and development of the detector
The readout chip was developed. It incorporates an array of 512x512 pixels with the top metal layer of the CMOS process being used as in-pixel electrode to contact in each pixel the bottom side of a photon absorber deposited on top of the pixel array. In parallel to this development, the development of the perovskite photon absorber layer continued. During chip fabrication by the foundry, a sensor PCB as well as a main PCB were developed to enable characterization of the chip. On receipt of the wafers, chips were assembled on PCB and tested electrically. Simultaneously chips were coated with a photon absorber. In addition to perovskite, a photon absorber made of quantum dots was also deposited by a Dutch start-up, QDI.
WP4 – Integration and evaluation of the prototype in laboratory environment
The sensor was characterized with X-ray and optically. The sensor with the quantum dot photon absorber gave the best results, with a single photon absorber being sensitive to X-ray, visible and IR up to a wavelength of 1300 nm. First test were performed on a composite part made of a honeycomb structure. Imaged with X-ray, the internal structure could be seen very clearly.
WP5 – Validation
The sensor was used to analyse by X-ray a piece of composite with defects inenationally inserted (delamination, inclusions, folding of layers), showing the ability of the sensor to detect defects in a composite part.
WP6 – Project management, communication, dissemination and exploitation
Dissemination and communication activities included presentations at the RADOPT’2021 and RADOPT’2023 workshops, articles in the CSEM Scientific and Technical reports 2021 and 2023 and a flyer.
WP1 - configuration and requirement definition
The functional and operational requirements of the sensor to be developed have been established, as well as the definition of the physical, electrical and mechanical interfaces of the system. The types of defects to be detected has also been defined, composite structures incorporating such defects have been fabricated to serve as references.
WP2 - Preliminary evaluation of the sensing technology
Starting from the requirements established in WP1, the system specifications and the sensor specifications have been derived, in particular the spectral range which must cover X-ray, visible and near infrared photons. For this purpose, two types of materials have been investigated, perovskite and sol-gel and optimized to extend their sensitivity in the near infrared band. Perovskite enables direct conversion from photon to electrical charges, while the use of sol-gel leads to an indirect conversion from near-infrared photons to visible photons. Patterning of different kind of perovskite materials was also studied to selectively optimize pixels for a specific spectral range (X-ray, visible or near infrared). Both technologies achieved near infrared sensitivity. Due to its high conversion efficiency, high X-ray absobtion coeffcicient and long term interesting perspectives, perovskite was retained as the material to be used for the demonstrator.
WP3 – Design and development of the detector
The readout chip was developed. It incorporates an array of 512x512 pixels with the top metal layer of the CMOS process being used as in-pixel electrode to contact in each pixel the bottom side of a photon absorber deposited on top of the pixel array. In parallel to this development, the development of the perovskite photon absorber layer continued. During chip fabrication by the foundry, a sensor PCB as well as a main PCB were developed to enable characterization of the chip. On receipt of the wafers, chips were assembled on PCB and tested electrically. Simultaneously chips were coated with a photon absorber. In addition to perovskite, a photon absorber made of quantum dots was also deposited by a Dutch start-up, QDI.
WP4 – Integration and evaluation of the prototype in laboratory environment
The sensor was characterized with X-ray and optically. The sensor with the quantum dot photon absorber gave the best results, with a single photon absorber being sensitive to X-ray, visible and IR up to a wavelength of 1300 nm. First test were performed on a composite part made of a honeycomb structure. Imaged with X-ray, the internal structure could be seen very clearly.
WP5 – Validation
The sensor was used to analyse by X-ray a piece of composite with defects inenationally inserted (delamination, inclusions, folding of layers), showing the ability of the sensor to detect defects in a composite part.
WP6 – Project management, communication, dissemination and exploitation
Dissemination and communication activities included presentations at the RADOPT’2021 and RADOPT’2023 workshops, articles in the CSEM Scientific and Technical reports 2021 and 2023 and a flyer.
The SWISSMODICS consortium has delivered an ultra-thin sensor module containing an image sensor sensitive to X-ray, near-infrared and visible light, based on sensitive layers deposited on top of a readout chip. Demonstrated on a composite panel incorporating faults such as delamination, it is a first step toward the integration of imaging sensors within the airframe structure. This technology will ease structural monitoring of airplanes reducing immobilization time and enabling more frequent monitoring of critical parts. It can be used for non-destructive testing and structural monitoring outside of the aeronautical field. However, its application is not limited to non-destructive testing. The material used is a very good X-ray absorber, enabling to minimize the irradiation dose. This is of paramount importance in the medical field, where this technology offers very interesting perspectives. Furthermore, it can also be optimized for ultra-violet, enabling the development of multispectral imagers covering the ultra-violet to near-infrared spectrum.