太大、太小、太$O_2$：来自氧梯度的潘多罗效应在体积分层增材制造中的表现
Too Big, Too Small, Too $O_2$: The Pandoro Effect from Oxygen Gradients in Tomographic Volumetric Additive Manufacturing
AI总结：
本文研究了体积分层增材制造中因氧梯度导致的潘多罗效应，提出多级策略通过光化学优化模型和工艺干预抑制该现象，提升生物打印的可重复性。
摘要：
体积分层增材制造（TVAM）能够实现快速、无层生物打印；然而其在热可逆水凝胶中的应用常受限于复杂的化学动力学。本文识别并表征了一种反复出现的打印缺陷——称为潘多罗效应，其表现为由于容器底部过早聚合和顶部抑制导致的截断锥形畸变。我们证明该现象源于树脂制备热滞后引起的垂直氧梯度：加热会消耗溶解氧，而随后冷却会从空气-树脂界面限制扩散重新供氧。为缓解此问题，我们提出多级策略。首先，我们引入一个耦合射线光学和光化学优化模型，严格考虑空间异质抑制剂浓度。不同于传统阈值方法，该可微框架显式模拟氧耗尽的时空反应-扩散动力学，使反求求解器能够预测性补偿局部抑制梯度。此外，我们验证了两种工艺干预：消除空气-树脂界面和控制头空间气氛。我们证明这些策略有效抑制潘多罗效应，并与细胞负载树脂兼容。本文为可重复的体积分层打印提供了指南，并扩展了我们的开源Dr.TVAM平台，使其具备先进的聚合建模能力。
英文摘要：
Tomographic Volumetric Additive Manufacturing (TVAM) enables rapid, layerless biofabrication; however, its application to thermoreversible hydrogels is often compromised by complex chemical kinetics. In this study, we identify and characterize a recurrent printing artifact - termed the Pandoro effect - manifesting as a truncated-cone distortion caused by premature polymerization at the vial bottom and inhibition at the top. We demonstrate that this phenomenon originates from a vertical oxygen gradient driven by the thermal hysteresis of resin preparation: heating depletes dissolved oxygen, while subsequent cooling induces diffusion-limited re-oxygenation from the air-resin interface. To mitigate this, we present a multi-tiered strategy. First, we introduce a coupled ray-optical and photochemical optimization model that rigorously accounts for spatially heterogeneous inhibitor concentrations. Unlike conventional threshold-based approaches, this differentiable framework explicitly simulates the spatiotemporal reaction-diffusion dynamics of oxygen depletion, allowing the inverse solver to predictively compensate for local inhibition gradients. Complementing this algorithmic correction, we validate two process-based interventions: the elimination of the air-resin interface and the control of headspace atmosphere. We demonstrate that these strategies effectively suppress the Pandoro effect, and are compatible with cell-laden resins. This work establishes guidelines for reproducible volumetric bioprinting and expands our open-source Dr.TVAM platform with advanced polymerization modeling capabilities.
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