Organic actuators for biomedical haptics and as tools for understanding the tactile sense

触觉在医学科学中的重要性几乎不可能被夸大。例如，触诊（通过触摸检查）是初级保健、骨科、产科、泌尿科、肿瘤学和语言病理学的一线诊断工具。此外，触摸是所有手工操作的关键部分。矫正骨折和脱臼的关节，翻转臀位婴儿，以及几乎所有的手术。对于位于城市和农村“医疗沙漠”的社区来说，触摸将大大提高远程患者就诊或基于药店的诊断测试的价值。尽管虚拟触觉在远程护理、医疗培训和机器人辅助手术方面很有吸引力，但医疗触觉技术还不发达。原因是现有的系统无法模仿生物组织的质地、柔软度、湿润度、导热性、粘性和其他近表面特性。该项目的关键假设是，要模拟这些感觉，需要能够实时改变其机械、电气和热性能的材料。这样做的方法是开发一个触觉设备系统，即可以刺激触觉的设备，基于可以产生可以动态转换的感觉的材料。粗糙与光滑，热与冷，黏与滑。提出了三种基于(1)导电聚合物的设备，以再现精细纹理的感觉；(2)液晶弹性体阵列，可以根据光线改变其柔软度；(3)热塑性塑料，可以在很小的温度变化下从橡胶变硬，从而给人一种虚拟物体的坚固和弹性的感觉。利用这些“触觉生物材料”的灵活性和可穿戴性，研究人员将制造一种原型触觉手套，允许人类用户通过触摸来区分虚拟物体。通过探索有机材料和心理学等不同领域的交叉点，该项目将为研究人员提供一个新的工具包，以更广泛地理解生物系统中的触觉和机械感知。研究和教育将通过以下活动相结合：(1)为代表性不足的少数民族学生提供实习机会；(2)将研究结果整合到研究人员的研究生和本科课程中；(3)在YouTube上制作一个关于触觉感知科学的视频系列，以及利用制作科学和教育视频的大量经验制作该项目的结果。这项研究的长期目标是使用触觉设备的组合，同时利用多种效果来实现热和冷，硬和软，粗糙和光滑，毛茸茸和鳞片，或粘和滑的感觉。这个项目的重点是测试一个假设，即由刺激响应聚合物制成的致动器——“有机致动器”——可以为“现成”组件无法提供的生物医学触觉设备提供新型的感觉。有机致动器被定义为由聚合物材料制成的结构，其氧化态、电导率、相行为、分子构象或填料结构可以通过电、光学或热刺激实时改变，从而产生宏观效应。研究计划分为三个任务，每个任务都使用有机驱动器产生的不同物理效果来产生触觉。第一项任务的重点是通过空间分辨的触觉电信号进行电刺激。一种可拉伸的导电聚合物在电极阵列中形成图案，产生电触觉信号，该信号将用于测量两点分辨率的刺激，并产生空间分辨率的感觉。研究的目的是验证这样一个假设，即小尺寸的电极，以及在专门设计的多路插座中单独处理它们的能力，可以用来产生在x-y平面上转换的感觉，从而产生运动感。人类受试者志愿者将采用双盲方法进行测试。第二项任务的重点是由液晶弹性体（LCE）产生的光学机械刺激，液晶弹性体（LCE）会根据光线改变形状，从而在指尖产生可变柔软度、纹理和运动的感觉。设计了一组实验来测量柔软阈值，该阈值可以通过改变LCE的弹性模量随辐照强度的变化而实时改变。第二组实验将使用LCE微柱阵列，这些微柱可以在光照下移动，让人类受试者感受到不同的纹理，甚至可能在指尖保持固定位置的情况下也能感受到移动界面的感觉。第三项任务的重点是通过嵌入纺织手套的热塑性聚合物提供热激活的动觉反馈。当加热或冷却刚好高于或低于其玻璃化转变温度时，手套将经历从僵硬到柔软的可逆变化，从而引发动觉反应。对手套温度的控制可以通过配对热敏电阻来实现，热敏电阻可以根据热波动改变其电阻，热电装置可以稳定温度，从而稳定基板的刚度。为了实现人机界面，手套上安装了弯曲传感器来控制机器人手指，机器人手指的尖端有一个压力传感器，当被激活时，它会向手套里的热电装置发送信号来冷却（使手指变硬），从而向用户提供动觉反馈。一旦确定了产生动觉反应所需的刚度阈值，所获得的信息将用于设计虚拟现实中的游戏，要求参与者抓住视觉上出现的物体，并识别哪些是实体的，哪些只是图像。最后，纹理信息将被编码到实体物体中，以确定是否有可能通过嵌入在前面任务中描述的类型的触觉致动器来区分物体。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The importance of the sense of touch in the medical sciences is nearly impossible to overstate. For example, palpation (examining by touching) is a first-line diagnostic tool in primary care, orthopedics, obstetrics, urology, oncology, and speech pathology. Moreover, touch is a key part of all procedures performed by hand--e.g., setting broken bones and dislocated joints, turning breech babies, and nearly all surgeries. For communities located in urban and rural "healthcare deserts," touch would greatly enhance the value of remote patient visits or drug-store-based diagnostic tests. Despite the attractiveness of virtual touch for remote care, medical training, and robot-assisted surgery, medical haptic technologies are underdeveloped. The reason is that existing systems cannot mimic the texture, softness, wetness, thermal conductivity, tack, and other near-surface properties of biological tissue. The key hypothesis of this project is that to mimic these sensations requires materials that can change their mechanical, electrical, and thermal properties in real time. The approach for doing so is to develop a system of haptic devices, i.e., devices that can stimulate the sense of touch, based on materials that can create sensations that can be transformed dynamically--e.g., rough vs. smooth, hot vs. cold, and sticky vs. slimy. Three types of devices are proposed based on (1) electricity conductive polymers to reproduce the feeling of fine texture, (2) arrays of liquid crystal elastomers that can change their softness in response to light, and (3) thermoplastics that can go from rubbery to stiff with small temperature changes to give the feeling of solidness and elasticity of virtual objects. Leveraging the flexible, wearable nature of these "haptic biomaterials," the investigators will build a prototype haptic glove that will allow a human user to differentiate between virtual objects by touch. By exploring the intersection of very different fields--organic materials and psychology--this project will provide a new toolkit for researchers to understand the tactile sense and mechanical sensing in biological systems more broadly. Research and education will be integrated through the following activities: (1) creation of internships for underrepresented minority students, (2) integration of the results into the investigators' graduate and undergraduate courses, and (3) creation of a video series on YouTube on the science of tactile perception and the results of this project which leverages considerable experience in creating scientific and educational videos.The long-term goal of this research is to use combinations of haptic devices that exploit multiple effects simultaneously to achieve sensations of hot and cold, hard and soft, rough and smooth, furry and scaly, or sticky and slimy. The focus of this project is on testing the hypothesis that actuators made from stimulus-responsive polymers--"organic actuators"--can supply new types of sensations for biomedical haptic devices unavailable to "off-the-shelf" components. Organic actuators are defined as structures made from polymeric materials whose oxidation state, electrical conductivity, phase behavior, molecular conformation, or packing structure can be altered by an electrical, optical, or thermal stimulus in real time to produce macroscopic effects. The Research Plan is organized under three tasks, each of which generates a tactile sensation using a different physical effect generated by an organic actuator. The FIRST Task is focused on electrical stimulation via spatially resolved electrotactile signals. A stretchable conductive polymer patterned into an array of electrodes generates an electrotactile signal that will be used to measure two-point resolution of stimulation and generate spatially resolved sensations. Studies are designed to test the hypothesis that the small size of the electrodes, along with the ability to address them individually in a purpose-designed multiplexed socket, can be used to produce sensations that translate in the x-y plane to give the sensation of motion. Human subject volunteers will be tested using a double-blind methodology. The SECOND Task is focused on optically-enabled mechanical stimulation created by a liquid-crystal elastomer (LCE) that undergoes a change in shape in response to light to generate sensations of variable softness, texture, and motion at the fingertip. One set of experiments is designed to measure softness thresholds that can be changed in real time by altering the elastic modulus of the LCE with the intensity of irradiation. A second set of experiments will use arrays of LCE microposts that can be moved with illumination to give human subjects the sense of feeling different textures and possibly the sensation of moving interfaces even as the fingertip maintains a fixed position. The THIRD Task is focused on providing thermally-enabled kinesthetic feedback via a thermoplastic polymer embedded into a textile glove. When heated or cooled just above or below its glass transition temperature, the glove will undergo a reversible change from stiff to soft to elicit a kinesthetic response. Control over the temperature of the glove can be achieved by pairing a thermistor that changes its resistance in response to thermal fluctuations, with the thermoelectric devices to stabilize the temperature and therefore the stiffness of the substrate. To achieve a human-machine interface, the glove has been fitted with flex sensors to control a robotic finger on whose tip there is a pressure sensor which, when activated, sends a signal to the thermoelectric devices in the glove to cool (stiffen the finger) and thus provide kinesthetic feedback to the user. Once the thresholds for stiffness required to generate a kinesthetic response are determined, the information gained will be used to design a game in virtual reality that asks participants to grasp objects that appear visually and identify which is solid and which is merely an image. Finally, textural information will be encoded in the solid objects to determine if it is possible for subjects to discriminate between objects by embedding haptic actuators of the type described in previous tasks.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.