IBEC Seminar. Sung Hoon Kang
viernes, julio 25 @ 10:00 am–11:00 am
Bone-inspired materials with self-adaptable mechanical properties and rose prickle-inspired sutureless anastomosis devices for resilient and healthy future
Sung Hoon Kang, Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology
I will present our ongoing efforts to address current challenges in materials for structural/biomedical applications and surgical procedures to connect blood vessels together based on inspiration from nature.
First, I will present self-adaptive materials that can change their mechanical properties depending on loading conditions by the coupling between loading and material synthesis [1]. Bone provides structural support for human body, and it has been a subject of study and inspiration for novel materials due to its outstanding mechanical properties including toughness, self-healing, and remodeling capability, which is desirable to mitigate the failure of materials and structures through fracture and fatigue. However, it has been challenging for synthetic materials to change and adapt their structures and properties to address the changing loading condition to prevent failure.
To address the challenge, we are inspired by the findings that bones are formed by mineralizing ions from blood onto collagen matrices. I will present a material system that triggers proportional mineral deposition from electrolytes on piezoelectric matrices upon mechanical loadings so that it can self-adapt to mechanical loadings. For example, the mineralization rate could be modulated by controlling the loading condition, and a 30-180% increase in the modulus of the material was observed upon varying the cyclic loading condition. Moreover, our results showed that minerals were preferentially formed near the crack tip where stress was concentrated so that they contribute to blunting the crack tip and mitigating the propagation of the damage. As a result, the material system showed a decrease in crack propagation speed by ~90%, compared to samples tested in deionized water without mineral ions.
To expand the environment that the material can be utilized, we have investigated synthesis of liquid-infused porous piezoelectric composites inspired by bone and pitcher plant [2]. I will present our synthesis approach and resulting mechanical properties. The material showed over 36 times increase in modulus and 30 times increase in dissipation after 12 million loading cycles, demonstrating self-adaptive behavior in air. Furthermore, the material can be (re)programmed to generate multiple shapes by self-folding based on spatial distribution of mechanical loading. [3]. We envision that our findings can contribute to new strategies for making resilient and sustainable materials for dynamically changing mechanical environments, with potential applications including infrastructure, vehicle, and healthcare [4].
Second, I will present biomedical devices that can connect blood vessels together without suture. Vascular anastomosis, the surgical connection of adjacent blood vessels, is a foundational surgical skill critical for plastic and reconstructive surgery, transplant surgery, vascular surgery, and many other surgical specialties. The current standard of anastomosis is manually suturing two tubular structures together around an opening with fine sutures often requiring a microscope or vessel loupes. This is a century old technique with many challenges. Suturing technique requires extensive surgical training in resource-intensive settings. Procedures are long (60 to 90 minutes per anastomosis), expensive (up to $35,000 per procedure), and, at times, require specialized equipment (surgical microscope costing over $100,000 per unit). Even in the hands of skilled surgeons, the anastomosis can be complicated by leakage or thrombosis; 27% of cases result in complications and 25% require reoperation. Consequently, there is a pressing need for a more efficient and safer alternative to handsewn anastomosis.
Inspired by rose prickles that are used by the plant for climbing walls, we report a sutureless anastomosis device with anchors designed to hold free vascular ends together with traction. We utilized 3D printing to find an optimum geometry of anchors by conducting ex-vivo tensile testing and flow measurements, as well as in-vivo testing with porcine models. We identified an optimum geometry from ex-vivo testing with porcine vessels, which showed the failure force of our device is comparable or better than that of the handsewn suture (4.9 N) with stretch force tolerance up to 6.3 N. Based on pulsatile flow testing with porcine vessels, we found no leakage up to 45 mL/min flow rate, well above the physiologic blood flow rate in a microvascular flap after anastomosis (13.7±5 mL/min). Compared with handsewn anastomosis, the device resulted in minimum deformation of the anastomotic site. From in-vivo non-survival porcine studies (N=10), the device showed successful anastomosis (< 5 min per anastomosis) with no leaking for both arterial and venous anastomoses. There was no thrombosis or other technical failure identified during the 4-hour observation period after device implantation. Our anastomotic device has the ability to innovate the way blood vessels are put together making current procedures faster, easier, and safer. We envision our sutureless anastomotic device will contribute to significantly improve medical readiness and make anastomotic techniques more accessible to a broad range of clinicians, researchers, and patients across the world.
