Experimental and data analysis workflow for soft matter nanoindentation

Nanoindentation refers to a class of experimental techniques where a micrometric force probe is used to quantify the local mechanical properties of soft biomaterials and cells. This approach has gained a central role in the fields of mechanobiology, biomaterials design and tissue engineering, to obtain a proper mechanical characterization of soft materials with a resolution comparable to the size of single cells (μm). The most popular strategy to acquire such experimental data is to employ an atomic force microscope (AFM); while this instrument offers an unprecedented resolution in force (down to pN) and space (sub-nm), its usability is often limited by its complexity that prevents routine measurements of integral indicators of mechanical properties, such as Young's Modulus (E). A new generation of nanoindenters, such as those based on optical fiber sensing technology, has recently gained popularity for its ease of integration while allowing to apply sub-nN forces with µm spatial resolution, therefore being suitable to probe local mechanical properties of hydrogels and cells. In this protocol, a step-by-step guide detailing the experimental procedure to acquire nanoindentation data on hydrogels and cells using a commercially available ferrule-top optical fiber sensing nanoindenter is presented. Whereas some steps are specific to the instrument used herein, the proposed protocol can be taken as a guide for other nanoindentation devices, granted some steps are adapted according to the manufacturer's guidelines. Further, a new open-source Python software equipped with a user-friendly graphical user interface for the analysis of nanoindentation data is presented, which allows for screening of incorrectly acquired curves, data filtering, computation of the contact point through different numerical procedures, the conventional computation of E, as well as a more advanced analysis particularly suited for single-cell nanoindentation data

Properties characterization of PDMS/Beeswax composite

Mestrado de dupla diplomação com a UTFPR - Universidade Tecnológica Federal do ParanáPolydimethylsiloxane (PDMS) is one of the elastomers belonging to the polymers that has received the most attention, as it is a material with good thermal stability, biocompatibility, flexibility, low cost and hyperplastic characteristics. As well as PDMS, beeswax, too, has attracted the attention of researchers, as it is a biodegradable material, thermally stable and of natural origin. These materials can be used in areas such as microfluidic systems, medical devices, electronic components, among others. PDMS mixed with beeswax is able to improve hydrophobic properties, abrasion and corrosion resistance, thermal stability and high temperature transparency. However, the manufacturing process used to mix PDMS and waxes requires some steps, such as heating, mixing and degassing, however, conventional methods do not follow a standardized process, resulting in products with low repeatability. To overcome this limitation, a vacuum chamber was developed and built with the objective of optimizing the manufacturing process. Another important factor is the use of beeswax, as it is a natural product, the composition is different depending on the climate and region. For this reason, in this study, the chemical characterization of beeswax was performed. Subsequently, experimental tests were carried out with the composite of PDMS and beeswax. Samples were manufactured using the multifunctional vacuum chamber developed in this dissertation. The samples were submitted to tensile, hardness, DMA, TGA, spectrometry and wettability tests in order to analyze the mechanical, optical and wettability properties. The manufacture of the multifunctional vacuum chamber allowed the production of samples with more uniform properties and made the process more efficient. In the DMA test, the composite showed thermal stability up to 200°C, together with high transparency at 80°C, when compared to pure PDMS. In the wettability test, the composite proved to increase the contact angle close to 150°C, presenting a super-hydrophobic surface.O polidimetilsiloxano (PDMS) é um dos elastómeros pertencente aos polímeros que mais tem recebido atenção, por ser um material com boa estabilidade térmica, biocompatibilidade, flexibilidade, baixo custo e características hiperplásticas. Assim como o PDMS, a cera de abelha, também, tem atraído a atenção dos investigadores, por se tratar de um material biodegradável, termicamente estável e de origem natural. Esses materiais podem ser utilizados em áreas como sistemas microfluídicos, dispositivos médicos, componentes eletrónicos, entre outros. O PDMS misturado com cera de abelha, mostra-se capaz de melhorar as propriedades hidrofóbicas, resistência à abrasão e corrosão, estabilidade térmica e transparência a alta temperatura. Porém, o processo de fabricação utilizado para misturar PDMS e ceras requer algumas etapas, como aquecer, misturar e desgaseificar, contudo, os métodos convencionais não seguem um processo normalizado, originando produtos com baixa repetibilidade. Para contornar esta limitação, desenvolveu-se e construiu-se uma câmara de vácuo com o objetivo de otimizar o processo de fabricação. Outro fator importante é a utilização da cera de abelha por ser um produto natural, a composição é diferente dependendo do clima e da região. Por esse motivo, neste estudo foi realizado a caracterização química da cera de abelha. Posteriormente, foram realizados testes experimentais com o compósito de PDMS e cera de abelha. O fabrico das amostras foi efetuado utilizando a câmara de vácuo multifuncional desenvolvida nesta dissertação. As amostras foram submetidas a ensaios de tração, dureza, DMA, TGA, espectrometria e de molhabilidade com o intuito de analisar as propriedades mecânicas, óticas e de molhabilidade. A fabricação da câmara de vácuo multifuncional permitiu a produção das amostras com propriedades mais uniformes e tornou o processo mais eficiente. No ensaio de DMA, o compósito mostrou uma estabilidade térmica até os 200°C, juntamente com a alta transparência a 80°C, quando comparado ao PDMS puro. No ensaio de molhabilidade, o compósito provou aumentar o ângulo de contacto perto dos 150°C, apresentado uma superfície super-hidrofóbica

Biomechanical Assessment and Monitoring of Thermal Ablation Using Harmonic Motion Imaging for Focused Ultrasound (HMIFU)

Cancer remains, one of the major public health problems in the United States as well as many other countries worldwide. According to the World Health Organization, cancer is currently the leading cause of death worldwide, accounting for 7.6 million deaths annually, and 25% of the annual death was due to Cancer during the year of 2011. In the long history of the cancer treatment field, many treatment options have been established up to date. Traditional procedures include surgical procedures as well as systemic therapies such as biologic therapy, chemotherapy, hormone therapy, and radiation therapy. Nevertheless, side-effects are often associated with such procedures due to the systemic delivery across the entire body. Recently technologies have been focused on localized therapy under minimally or noninvasive procedure with imaging-guidance, such as cryoablation, laser ablation, radio‐frequency (RF) ablation, and High Intensity F-ocused Ultrasound (HIFU). HIFU is a non-invasive procedure aims to coagulate tissue thermally at a localized focal zone created with noninvasively emitting a set of focused ultrasound beams while the surrounding healthy tissues remain relatively untreated. Harmonic Motion Imaging for Focused Ultrasound (HMIFU) is a dynamic, radiation-force-based imaging technique, which utilizes a single HIFU transducer by emitting an Amplitude-modulated (AM) beam to both thermally ablate the tumor while inducing a stable oscillatory tissue displacement at its focal zone. The oscillatory response is then estimated by a cross-correlation based motion tracking technique on the signal collected by a confocally-aligned diagnostic transducer. HMIFU addresses the most critical aspect and one of the major unmet needs of HIFU treatment, which is the ability to perform real-time monitoring and mapping of tissue property change during the HIFU treatment. In this dissertation, both the assessment and monitoring aspects of HMIFU have been investigated fundamentally and experimentally through development of both a 1-D and 2-D based system. The performance assessment of HMIFU technique in depicting the lesion size increase as well as the lesion-to-background displacement contrast was first demonstrated using a 3D, FE-based interdisciplinary simulation framework. Through the development of 1-D HMIFU system, a multi-parametric monitoring approach was presented where presented where the focal HMI displacement, phase shift (Δφ), and correlation coefficients were monitored along with thermocouple and PCD under the HIFU treatment sequence with boiling and slow denaturation. For HIFU treatments with slow denaturation, consistent displacement increase-then-decrease trend was observed, indicating tissue softening-then-stiffening and phase shift increased with treatment time in agreement with mechanical testing outcomes. The correlation coefficient remained high throughout the entire treatment time under a minimized broadband energy and boiling mechanism. Contrarily, both displacement and phase shift changes lacked consistency under HIFU treatment sequences with boiling due to the presence of strong boiling mechanism confirmed by both PCD and thermocouple monitoring. In order to facilitate its clinical translation, a fully-integrated, clinically 2D real-time HMIFU system was also developed, which is capable of providing 2D real-time streaming during HIFU treatment up to 15 Hz without interruption. Reproducibility studies of the system showed consistent displacement estimation on tissue-mimicking phantoms as well as monitoring of tissue-softening-then-stiffening phase change across 16 out of 19 liver specimens (Increasing rate in phase shift (Δφ): 0.73±0.69 %/s, Decreasing rate in phase shift (Δφ): 0.60±0.19 %/s) along with thermocouple monitoring (Increasing: 0.84±1.15 %/ °C, Decreasing: 2.03± 0.93%/ °C) and validation of tissue stiffening using mechanical testing. In addition, the 2-D HMIFU system feasibility on preclinical pancreatic tumor mice model was also demonstrated in vivo, where HMI displacement decreases were observed across three of five treatment locations on the kP(f)c model at 20.8±6.84, 18.6±1.46, and 24.0±5.43%, as well as across four of the seven treatment locations on the KPC model at 39.5±2.98%, 34.5±21.5%, 16.0±3.05%, and 35.0±3.12% along with H and E histological confirmation. In order to improve the quantitative monitoring aspect of HMIFU, a novel, model-independent method for the estimating Young's modulus based on strain profile was also implemented, where 1-D HMIFU system showed feasibilities on polyacrylamide phantom (EHMI/E ≈ 2.3) and liver specimen (EHMI/E ≈ 8.1), and 2-D HMIFU system showed feasibilities on copolymer phantom(EHMI/E ≈ 30.4), liver specimen(EHMI/E ≈ 211.3), as well as HIFU treated liver specimen (EHMI,end/EHMI,beginning ≈ 5.96). In conclusion, the outcomes from the aforementioned studies successfully showed the feasibility of both HMIFU systems in multi-parametric monitoring of HIFU treatment with slow denaturation and boiling, which prepares its stage towards clinical translation